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BLAM! The shot was noticeably loud and snappy. Then again I was shooting full-house 10mm. Debris peppered my face. “What the heck?” I thought it was dirt or bullet material ricocheting back from downrange. But the stinging in my hands reached my brain and I looked down at my GEN3 GLOCK 20SF to find the right side of the frame blown out, the mag release missing, and my strong hand reassigned to a different location on the grip.

I promptly swore (warning: there’s some choice language in the video) and threw the gun down on the ground in front of me (pointed downrange, of course). As I was shooting from a kneeling position the snow-covered ground was the best place to put it.

First step, of course, was taking stock of myself. Everything was still attached. There was no blood or open wounds. Good lord did my hands sting. Probably didn’t help that they were already really cold from shooting outside in snowy conditions for a few hours. Damn, I wish I’d been wearing gloves. They at least would have prevented that pressure-blasted carbon soot from staining my skin — a nice, straight line down my thumb from the slide/frame gap, around the web of my hand from the same, and in various other areas.

I am, however, very glad I had eye protection on. I took off the silly sunglasses I wear in most of my videos and put on actual, safety-rated lenses since I was off camera. Not that the sunglasses wouldn’t have been sufficient. There was no damage to my face as I’d only received a minor sandblasting of insignificant debris. But it could have easily been a very different scenario.

As you may have guessed from the first photo, the right side of the magazine release attempting to reach low earth orbit did the most damage. It was fully covered by my strong side hand in a solid grip, lined up with the bottom of my trigger finger. Practically right in the web between trigger finger and middle finger, really.

With the gun kicking back from the very stout recoil and the top of the frame popping outwards, it appears to have moved my hand enough such that the mag release smacked the first knuckle on my index finger as it escaped over the top. The photo above was taken three days later and shows some of the broken blood vessels and light bruising. It was tender but really not that bad at all, and that’s the extent of the damage I suffered.

It’s fair to say that my GLOCK absorbed the brunt of the blast.

Inside the slide was a Lone Wolf 6.6-inch threaded barrel and a 21-lb. recoil spring. I’ve shot hundreds of rounds of 10mm ammo through this setup without a hiccup. As it turned out, I was likely lucky this barrel, with its better case support than the factory one, was in the gun at the time.

The mag release button almost escaped the left side of the frame, too.

Significant gas pressure clearly shot down into the magazine. It broke through the front of the follower, popped the magazine almost entirely out of the frame, and caused it to expand so much that it split the polymer overmold right down to the baseplate. When I removed the magazine from the gun, round number two was positioned exactly as seen above.

Loose chunks of plastic were rattling around inside the magazine.

Believe it or not, the frame popped right back into place and at that point everything (mag release excepted) still functioned. I was then able to verify that my G20 wouldn’t fire out of battery, striking that off the list of potential causes.

No part of the slide or components therein appeared damaged at all.

It was sure dirty, but nothing about the barrel appeared or measured out of spec as far as I could tell. It’s with Lone Wolf now for a full inspection, but I believe it survived the ka-boom without a scratch.

So, what caused the detonation? We know it wasn’t the gun firing out of battery and thanks to capturing the previous shot on video I was able to conclusively rule out the possibility of a barrel obstruction. Everything pointed to a bad round of ammunition.

The ammo in question was from Underwood Ammunition, a brand I know, trust, and have a great affinity for. Specifically, it was their 10mm loaded with Lehigh Defense‘s solid copper Xtreme Penetrator projectile.

I contacted Underwood and laid out my case, suggesting I believed it was almost unquestionably an ammo issue. Specifically, my guess was either a double charge (too much gunpowder in the case) or a loose bullet that was shoved down into the case when it fed, causing a pressure spike.

Underwood was extremely responsive, friendly, and helpful. They immediately stepped up to the plate and informed me that they would, at my preference, either replace everything that was damaged or would send me a check for the appropriate amount. I had only to send them a list of ruined items: one full-size GLOCK SF frame, one G20 magazine, one pair Kirkland Signature boy’s size extra medium underwear.

They also e-mailed me a shipping label so I could send the remaining ammo back to them for inspection. Underwood analyzed it and provided the following statement on the cause of my G20 kaboom:

After receiving the ammunition back and testing, we have determined that an anomaly in the projectile is what caused the malfunction in the firearm.

The issue has been resolved and we have invested in the most advanced inspection equipment available to ensure nothing like this will become an issue in the future. This equipment utilizes infrared laser technology to detect any inconsistencies in the rounds or projectiles. It is able to do so with far more scrutiny and accuracy than any other method we have come across.

We never want anyone to be in danger of destruction of property or, worst of all, injury while using our product. Safety and quality are our two most important goals when manufacturing ammunition.

Specifically, the projectile diameter was undersized. Even though the case was properly crimped, the bullet was easily pressed down into the casing (bullet setback) when the round fed into the chamber and this caused a sufficient spike in pressure to do the damage seen above.

I can only assume that Underwood will have a chat with Lehigh (also a brand I know and like, which has a solid reputation for making quality, innovative products and even won our Reader’s Choice Award last year) about this, but for Underwood’s part they didn’t change their tune about taking ownership and sending me a check. As far as they’re concerned it was their ammo and therefore their responsibility, and they’re going to make it right. Period. This level of customer service is certainly appreciated, and they’ve made the whole process as easy as it could possibly be.

For me, I still trust Underwood’s ammo and will continue to use it. I’ve been shooting (and browsing the interwebs) enough that I’ve seen serious ammunition malfunctions and kabooms from just about every major brand of ammunition available. This sort of thing is a risk we all assume as shooters. I’m thankful I wasn’t injured, thankful that Underwood handled it so nicely, and I think it’s great that they’re doubling down on inspection equipment to make sure even projectiles purchased from trusted manufacturers are measured before they’re loaded.

My main takeaways: always wear eye protection, keep a first aid/trauma kit in your range bag, guns and ammo are complex systems that can fail in dangerous ways, and I may just wear shooting gloves more often.

[UPDATE] Further input from Underwood Ammo regarding the question of a recall and expanding on the brief statement previously provided:

Looking back, I failed to clarify that the other projectiles that were found to be too small were not from the same box of ammo we sent you, but from the same shipment of projectiles we received from the manufacturer. We looked through all of those and found 4 additional projectiles in addition to the one that caused your malfunction. We also went through our shelves and check each round that had already been loaded and found no issues. We are extremely confident this issue is isolated and resolved.

We have, however, given great thought to a recall because we do not want anyone else to be put in harms way. As a result, we are contacting all customers who purchased the same lot number as you did and offering them an opportunity to exchange their box of ammo for a new one.

While we are confident this will not happen again, it simply isn’t worth risking anyone’s safety.

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    • GLOCK haters are going to come out of the woodwork here no matter what. But the GLOCK didn’t cause this, the ammo (undersized diameter projectile) did. The same massive pressure spike would have occurred in any pistol. That said…

      I’m willing to entertain the idea that, if this were a metal-framed gun, the frame may have survived without any damage. However, I still think it’s highly likely that the right side of the mag release would have been blown out of the frame and hurt my hand. Or that on many metal-framed guns the grip panels may have exploded off the frame and done worse damage to me. I have seen plenty of photographs of completely destroyed metal-framed pistols and rifles as well though where the metal itself cracked, broke, and became shrapnel so, no, I will not actually agree that a metal-framed pistol would have fared better in this specific case. And I’d take a ruined frame all day every day if it means it absorbed that energy and prevented the gun from grenading or otherwise transferring more of it into my hands instead.

      But I’d rather avoid the mental masturbation of the “what if” rabbit hole. Bottom line, this was not the GLOCK’s fault and there’s no way to actually know if I would have been better off or worse off were I shooting gun model XYZ instead.

      • Back in the early ’90’s when guys were making major power factor with .38 supers I remember more than one colt steel 1911 coming apart and giving the shooter “super face”.

        • Thanks for the trip in the way back machine! Look! Super Face!

          I remember seeing guys at IPSC matches in the 80’s walking around with a dozen+ little band-aids on their face after shooting .38 Super loads to make major power factor, and have all manner of weapon and case failures flying out of their 1911 to wear on their face. I would imagine the polymer’s flexibility allowed for some expansion before breaking, rather than the fragments typically seen on metal frame pistols with questionable metallurgy (which has come a long way in the recent decades). Any portion of the case that is unsupported becomes a potential failure point when you have an ammunition problem – so go easy on those feed ramps if you’re the young, unknowingly uninformed, aggressive, home gunsmithing type like I was 30 years ago (There’s a reason why I know this. Experience is what you get just seconds after you actually needed it.)

      • Same thing would have happened with an aluminum frame pistol. Steel I’m unsure about, but the pressure has to go somewhere.

        • It’s the dang rare steel-framed (or aluminum) gun that doesn’t have plastic, wood, or other synthetic-material grip panels on it. Maybe the steel would have held up, but ultimately if you think your hand is wrapped around nothing but steel you’re probably wrong. I’d guess that a one-piece FRP molded frame (e.g. Glock) is less likely to pop than separate grip panel pieces held to a steel frame by one or two screws.

          Except for the magazine release, the Glock frame appears to have vented the pressure above where my hand was. I’d gladly accept this over a frame that explodes under my hands because that’s where the weakest point is.

        • Indeed. 1911’s that have suffered case failures have often had the wood grip panels blown off – or splintered into the shooter’s hand, etc.

      • Not a fan of glocks…. but this is clearly not the glocks fault. I’m amazed it held up an well as it did.
        And props to the ammo company for taking this seriously and paying for the damage.
        Also glad you weren’t hurt any worse.
        Be safe out there everybody. This could’ve been any one of us.

      • Ah, yes, the Glock fanboys defend this failure. It’s *always* due to ammo. Yet when other guns go tits up, it’s the gun, never the ammo. Typical hilarity. You guys wouldn’t hear so much shit when something happens to your favorite pistol if you had a bit of humility and shut op once in a while about it’s infallibility.

        • @RickP — in case you’re directing that towards me or anything I said, you’re way off base. Not only is this incident well-documented and has been proven to be the fault of the ammo (by the ammo manufacturer, btw, who I’m sure would have preferred it were the gun’s fault), but I’m the guy who just said this gun is superior to the G19. I’m far from a Glock fanboy. I really don’t care at all what logo is on my guns, which is why I regularly carry a Beretta, an HK, a Glock, and a Taurus. And my competition pistol has been a CZ for a long time. A look inside my safe would dispel any thoughts you might have that I’m loyal to any given brand, let alone a fanboy of one.

          What you got in this article (as usual) is the straight truth. If it were the gun’s fault I would have said so. Period. No matter what gun it was. It was a coincidence that it happened while I was shooting a Glock. Minutes prior I was shooting that CZ P-10 and minutes before that I was shooting a Springfield. If they were all 10mms, whatever one loaded this round first would have blown up. Any semi-auto 10mm that loaded this round would have blown up to some degree. Period, full stop.

        • Guess reading and comprehension isn’t your strong suit. The manufacturer analyzed the returned ammo and determined it was their fault caused by the projectile diameter being undersized.

        • The requisite douchebag award for every internet comment section has found its recipient. Take a bow, sir, take a bow

      • The shooter escaped injury which proves superiority of glock guns. People often cannot see past the wreck to appreciate the safety features that worked. Instead they focus on the dents and scratches.

        Great article and follow through. Love my 29SF and Buffalo Bore.

        • “The shooter escaped injury which proves superiority of glock guns.”

          WTF? If this had happened while he was shooting an XD would you still be saying the same thing? C’mon man, it’s statements like that that start flame wars and are just so needless.

          BTW, he didn’t escape injury, though thank goodness it wasn’t more serious. If anything, the polymer frame may have alleviated some of the potential injury, and Glock isn’t the only one making those… Yes, I own an XD and love it. Yes, I am still considering getting a Glock. Not as a replacement mind you, but as an additional option. Probably a G19.

      • “And I’d take a ruined frame all day every day if it means it absorbed that energy and prevented the gun from grenading or otherwise transferring more of it into my hands instead.”


      • You can speculate without being an obvious Glock shill. Honestly, Glock advertising notwithstanding, Glock pistols are not “Perfection” any more than any other company’s products are, and its an insult to the intelligence of SOME of your readers to be talked down to like we’re too stupid to know that Glocks, particularly those of the .40 S&W and 10mm varieties, have a reputation for catastrophic failure. If the pistol wasn’t the problem, why are you defending it and the company? If you’re convinced the gun didn’t fail (whats up with the aftermarket parts in a high-quality firearm, by the way?), then there is no need to repeatedly mention a non-existent problem. Move on to the ammo and be done with it.

        Although as far as your shocked/dazed/bewildered (normal reaction after a KaBoom! and I speak from experience) analysis and diagnosis goes, I found your “pushed the frame fragments back together and found that it couldn’t fire out of battery” result kind of funny. About as funny as what may be the most ridiculous comments I’ve ever read about the possible superiority of shattered fragmented plastic over good old steel, which actually is ALSO plastic until it reaches its yield point and limits of its tensile strength. Typically well over 100,000 psi in most cases. Extremely cold steel can shatter. Pure, brittle cast iron can shatter. Extremely hard and brittle steel with a sky-high carbon content can shatter if not tempered. But good steel strong enough to survive hundreds and even hundreds of thousands of slide cycles in a quality pistol does not shatter when subjected to a very brief and rapidly diminished pressure spike as a case lets go inside a pistol frame.

        As for firing out of battery, Glocks must be amazingly precise in just that one regard, because even most 1911s will fire when very slightly out of battery but yet still closed enough to prevent catastrophy, and 1911s tend to be pretty tightly and precisely fitted everywhere. Whereas Glocks are pretty loose everywhere but yet Glock owners claim they are absolutely incapable of firing out of battery. Of course many of them tend to create some pretty funky firing pin “indentations” in primers that seem to suggest things maybe aren’t as precise and well-timed in Glocks as some believe and claim. And whether or not a Glock is actually “in battery” at all is questionable. Certainly Glocks do not lock up anywhere near as tightly or completely as most other pistols, and even a pistol that DOES fire slightly out of battery shouldn’t disintegrate, but back to your comments and speculation that just maybe plastic is better than steel in a KaBoom! situation. What immediately came to mind was that I should ask you if you’d rather have a plastic gun safe than a steel one or why gun barrels are not plastic if its potentially better at containing pressure than steel, but I’ll just pass along my own personal experience.

        As the proud owner of a Les Baer Premier II Tactical that I KaBoom!ed as a result of my own stupidity/negligence/error/inattention reloading, I can tell you for a fact that given a choice between KaBoom!ing ONE Glock and TEN 1911s, I’ll take the ten 1911s. I’ll even take KaBooming the same 1911 10 times. I had a catastrophic failure due to a probable overcharge and even with a fully supported case head about 1/3 of the case above the rim was relocated, the blast tried to bottom eject (and succeeded with 1.5 rounds) the remaining ammo out of the magazine, the mammoth ivory inserts in the Wilson Combat G10 grips (my only concern until we thankfully found them as they were a gift I had microscrimshawed by Bob Hergert) were blasted out, all of the lube in the gun was evacuated or cooked out and the recoil spring was dramatically detensioned. I had a little soot on my hands but no stinging, not bruises or blood blisters and no forceful “relocation” of my hands on the grip.

        The Wilson 47D was pretty well hashed with the follower broken in half lengthwise, but after finding the baseplate, prying the round sticking out the bottom out and sticking the magazine back together with the broken follower, I proceeded to give the pistol a once-over and got back on the horse and kept shooting. With the hashed recoil spring and gun running dry, I didn’t shoot much more but enough to satisfy myself the gun wasn’t damaged. True to the optional factory guarantee, it still manages 1.5″ groups at 50 yards and after a thorough cleaning, new spring and epoxying the ivory inserts back in the grips, its KaBoom! became just a bad memory and a good lesson.

        Actually I could blame the whole thing on the loose bullet someone apparently lost in a pound of powder that subsequently got returned and sold to me and ended up in my measure, but I don’t know for certain that was the problem. And not being a Glock shill, I don’t automatically blame every gun problem I have on bad ammo. Especially since I load everything I shoot except rimfire. As for “setback” being the cause of failures, I have a hard time believing that. Just like I KNOW the “double-charge/triple-charge” excuse is extremely unlikely in MOST cases and IMPOSSIBLE in the rest.

        Once you start loading ammo and get a feel for case capacities and how much powder will fit in various cases, you learn that while a double-charge or triple-charge of something like Titegroup would easily fit in a .45 ACP case, it’s virtually impossible to do the same with 9mm, .40 or 10mm. And since production reloading presses basically can’t deliver multiple charges unless the press is cycled multiple times without the turret being advanced, it’s pretty unlikely to happen reloading, too. Not impossible, but pretty hard to pull off. And that’s with a human being operating the press.

        With a motor drive press of the type I assume commercial ammo companies use, some significant malfunctions would have to occur, be unnoticed, repair themselves and production continue with no one noticing or taking any action if they did. A regular hand-operated thrower usually used with a single-stage press also has to be operated one full cycle per charge.

        It goes without saying that if in fact setback is an issue, its only because of the “generous” tolerances of certain pistol brands that commercial and private loaders of ammunition have to be very careful applying any crimp to pistol ammunition. Overcrimped ammunition causes pressure increases as well, and in a lose chamber with a loose throat, a tight crimp could lead to a case mouth trying to headspace in the throat instead of against it with various possible negative effects.

        And lest you think I’m one of those narrow-minded “plastic pistol haters”, I assure you I once leaned in that direction and still do when it comes to a certain brand some worship like a god. But I have an XD(M) Compact 3.8 in .40 (Springfield Armory and Smith & Wesson actually built .40s and installed 9mm barrels and slides on them instead of the other way around and also recognize the need for significantly stronger recoil springs on .40s) I bought on a whim to “flip” and have owned ever since I decided to put a few rounds through it before selling it. I also have a Ruger Mark III 22/45 Target and multiple high-powered rifles with “composite” stocks, including an M1A.

        And as a longtime mechanic I am very comfortable with and familiar with plastics and other “synthetic” materials. But there are places where steel is better and places where I prefer plastic over steel, such as in my XD(M). Which not only seems much better constructed than the few Glocks I’ve handled, it also shoots as well as my 1911s. Or at least as well as my R1. My Les Baer is kind of in a class of its own. Even after its bad day on the range.

        • I’m not a Glock fan. I begrudgingly own a couple because they were the right tool for the job, despite searching for excuses to get something else instead. A big reason I replaced the factory barrel in the first place was to feel comfortable shooting full-power 10mm as well as cast lead projectiles. I don’t trust the lack of chamber support in the factory barrel, which is why they got that reputation for case blowouts that you mentioned. With the LW barrel a lack of full case support didn’t cause this kaboom. I’m not excusing the gun because I’m a shill for Glock, but because I fixed the very problem you allude to and the lack of full case support on the factory barrel was simply not a factor here at all. You expect me to blame the design of the OEM barrel when it wasn’t in the gun? That’s absurd.

          The gun didn’t fire out of battery and wouldn’t fire out of battery. Yes, I was able to properly test this on my particular gun despite the crack in the frame. No, Glocks are not known for firing out of battery. In fact I’ve seen them singled out as a brand that’s particularly easy to make inoperable by slightly pressing back on the muzzle (actually, pressing the muzzle into something — a person…contact shots…with Glock mentioned by name during police and CQB and krav maga trainings as being very sensitive to this).

          It’s because I know where people will point fingers and try to lay blame that I spent time mentioning various non-existent problems. Troubleshooting and determining cause require ruling out variables. In this case I was able to rule out most potential causes of a kaboom such as this one, and the write-up would have been meaningless without discussing that process.

          Finally, not only did the manufacturer of the ammunition accept fault, but they found other loaded rounds in their inventory that exhibited the same problem. Sure, you can argue that it was the non-existent OEM barrel’s lack of case support that caused this or maybe it was aliens, but I’m pretty freaking sure it was the ammo.

      • I had a squib . 357 round shot as #3 in a string of 4 rapid fire shots in a drill. I was triggering the 4th shot as the sound of #3 registered flat and hollow. I also got miscellaneous pieces of metal and other debris in my face and arm below my elbow. the model 605 revolver was rebuilt from the frame out including the undamaged trigger mechanism, hammer and springs. Remington offered to pay but Taurus rebuilt it on warranty. I reload and always have a little twinge when shootin rapid fire. I’m stupid slow and careful at the. charging phase of reloading before but especially since then. It happened to me with a factory round so I really watch my reloads.

    • I really appreciate you showing us this. I will also take it as a lesson to visually inspect my ammo for any possible external anomalies. I know that this will not pick up internal anomalies but it still may be of help on those rare occasions.
      I truly respect the ammo company for stepping up and being honest with what happened and ensuring this type of thing does not happen again.
      Thank you.

  1. I’m trying to figure out how a detonation in a properly closed action can cause that kind of carnage without any apparent damage to the barrel or the breech? Did the case blow out in the unsupported area over the feed ramp?

    • Yes I have to assume the case blew out, and the amount of carbon burned onto the feed ramp and surrounding areas of the barrel suggests that did happen. How much pressure went out the front before it blew out the back won’t be known, though, of course.

      Unfortunately I couldn’t find the case. Lord knows how far it flew, but the snow would have made it almost impossible to find regardless. I looked a little bit, but there was just no way it was going to be found.

      • Sounds like an episode for Myth-Busters. One only needs to get a sh– pile of GLOCKS and just find out what kind of pressure is required to blow the gun apart. There has to be a range of pressure that GLOCKS begin to consistently fail. With that value or baseline pressure known, one could then create consistent over-pressure loads, then test other weapons to find out what holds together at those excessive pressures. Does a Sig P220 hold together at the same destructive pressure where a GLOCK fails? Interesting question. I’d be happy to see a sh– pile of GLOCKs get blown to pieces, all for the enhancement of personal safety of course 😉

        • Be more fun if mythbusters ran hot loads through Hi Points. And then used Glocks to shoot +p+ at Hi Points.

          Sorry Hi Point fanbouys.

        • There are multiple factors involved. Its Patrick Sweeney’s contention in his “Glock: Deconstructed” book (excellent read and you’ll know more than 99% of Glocksuckers in case you like trolling them) that Glocks “Tennifer” hardening process plays a roll in KaBoom!s where the barrel and chamber rearrange themselves. He has a degree in Chemistry and was a gunsmith so he actually knows what the hell he’s talking about. Something he doesn’t mention specifically but that popped into my mechanic mind is the square cross section of the barrel at the chamber itself. Typically pressure vessels are ROUND in cross section. Square corners create thin spots and stress risers. That coupled with a questionable hardening process that creates a very hard and very BRITTLE surface could be a ticking time bomb. Over time the remaining steel could work harden and fractures and stress risers could form until it finally comes unglued. And Glocks stupid refusal to design good recoil spring assemblies for its .40s and 10mm and build bigger, stronger frames and components for those pistols instead of slapping .40 and 10mm parts on 9mm frames is just asking for problems. Those larger barrels and slides are actually thinner and weaker. Real stupid when you think about it. Fortunately Glock has all its little acolytes trained to respond with “BAD AMMO!” every time any Glock experiences any failure and “LIMP WRIST!” any time one malfunctions, so they’re safe from massive uprisings from p.o.ed fanboys.

      • Uh, typically blown cases are found inside the pistol. That blown case is the ONLY thing I would have been interested in recovering. The undersize projectile and setback claim just don’t hold water. What people conveniently tend to ignore or forget about bullets that move easily enough for setback to be an issue is that a lack of case tension works both ways. A bullet that slides back easily also slides out easily. Especially given how so many bullets tend to be pointy in front and flat in back. Not to mention the case itself plays a role in case tension, which is also kind of obvious. You’ve established that it was FACTORY ammunition. Now the question is if it was NEW ammunition or if it was of the “remanufactured” variety. I ask because with a high-pressure, high-powered (right there with .44 Magnum according to the more “enthusiastic” 10mm fans) pistol cartridge, I can only assume that 10mm brass fired in Glocks could have that same Glock “smile” tendency as .40 S&W fired from Glocks, and that if an ammo company were reloading “once-fired” brass and running the 10mm and .40 S&W cases through one of those “de-smile” dies to make it “good as new”, they might jump at the chance to blame anything but questionable brass when they jumped at the chance to take the blame for a KaBoom! after seeing nothing but the unfired ammunition and gun remnants (personally they’d have gotten nothing but pictures from me if it were actually my gun) without seeing the failed cartridge itself. The other possibility is that they’re loading their 10mm on the hot end of “safe”, as 10mm fanboys seem to be addicted to all that power and recoil. Even when they’re just plinking. Personally, I want my guns, brass, powder supply and bank account to all last as long as possible, so I stay a good two steps below “Max” with pretty much everything I shoot. But that’s just me. I do have some pretty hot .45 Colt loaded and I bought a .460 Rowland conversion for my 1911s just to have a pistol that is ACTUALLY in .44 Magnum range to wave under the noses of 10mm fanboys, but other than that safe and sane is how I roll. But I just can’t get past having a catastrophic firearm failure and NOT recovering as much of the evidence and mangled wreckage as possible. That stuff is like a trophy to most guys. Or at the very least a teaching and remembering tool. I spent most of an hour crawling around on hands and knees on concrete and crushed rock looking for an eventually finding the two 1/2″ mammoth ivory disks out of my 1911 grips when I KaBoom!ed it. Granted they meant a lot more than the blown case. But I still have it, too.

        • Brand new. I think they use Starline brass in most cases. They are loaded to full power. There was no way whatever was left of the brass was going to be recovered in that snowy field without a metal detector.

  2. I don’t see a recall on Underwood’s website for this ammo and it is still listed for sale. I would think there were more boxes loaded from that lot than just the one you were using at the range. Maybe they are planning a statement or it is listed somewhere that I didn’t find.

    • It says they CONSIDERED a recall. But see below for why it was not done.
      They checked everything they had in stock and all were properly sized.

      Separately, they contacted each buyer prior to them checking. So, provided they didn’t send any of this lot to stores for resale, there is no need for a recall.

      I have never bought their ammo, just how I read the article.

  3. I saw this posted on Active Self Protection’s Facebook Page a couple days ago experimenting with bullet set back:

    If the same holds true for 10mm, I don’t think bullet set back played a big role. Likely, if the bullet diameter was undersized, an improper seal in the chamber could simply allow for the ignition of the powder and subsequent explosion to no longer be fully contained within the barrel.

    • .035″ isn’t much setback. That’s like a spark plug gap worth of bullet movement.

      The .40 S&W case also has less open room in which to set the bullet back or affect the volume of the cartridge. Indeed, the very reason for the creation of the .40 was because the nominal FBI loads in the 10mm left a fair bit of the case empty.

    • “…if the bullet diameter was undersized, an improper seal in the chamber could…”

      If it was undersized and made an incomplete seal in the barrel, wouldn’t the combustion gasses blow right by the projectile and exit the muzzle?

      I’m making the assumption that like water, pressurized gasses will find the path of least resistance and go there…

      • Undersized sufficiently to get forced down into the case upon chambering and undersized sufficiently to not seal in the barrel can be very different things. The bullet did leave the barrel, but clearly the pressure spike was large enough and fast enough to blow out into the frame before the bullet’s trip down and out the barrel allowed the pressure to drop. Leaking around the bullet more than usual or not, it wasn’t enough and pressure blew out both ends. I’m sure if I filled an empty case with C4 (no bullet at all…just an open case mouth) and detonated it in the chamber it would do a whole lot more than just blow hot air out the end of the barrel. At some point, there’s going to be enough pressure that it can’t escape down a pipe fast enough and it’s going to force its way out other places, too…

        • Backward pressure always happens. You call it recoil or cycling. I call it Newton’s third law.

        • The question is whether it’s enough to blow out the back of a case and pressurize the frame such that it explodes. (the answer in this case was “yes”)

    • I have to agree, if the bullet was that undersize, there may well have been not enough of a bullet seal to expand the case in the chamber enough to prevent tremendous amounts of gas to flow rearward. The initial bypass of gasses past the bullet may have gone both forward and rearward, but as the bullet moved forward it may have suddenly acted like a plug spectacularly forcing the case and the bolt to the rear with most of the power of the powder charge acting on them.

  4. Has Underwood issued a product recall for all the other rounds in that lot?

    And how did the failure develop?

    Was chamber pressure so high the brass was moved back out of the chamber allowing the combustion gasses to blow around the brass before the projectile exited the barrel?

    (As humorous aside, too bad you weren’t chrono-ing that shot. It would have been interesting seeing the velocity of that shot…)

    • No way to know exactly how it propagated. Bullet setback is a known cause of “kabooms,” though, due to the spike in pressure that happens from it. It’s why you see it mentioned over and over regarding carry ammo and why it’s generally a bad idea to chamber the same round repeatedly (e.g. come home, eject the chambered round before putting the gun away, then re-chamber it again the next day, repeat repeat repeat) since even a properly-crimped bullet can get incrementally driven down into the case from that. In this case the bullet diameter was too small, it wasn’t held in place even though the case was crimped to spec, and when it was chambered it was slammed down into the case which caused the excessive pressure.

      • With respect to bullet setback being a “known cause of kabooms”, do you have any documented instance of it other than Hornady’s speculation here? I’ve never thought of it (shooting a round with the bullet set back) as a problem and hadn’t even heard of such a thing being a problem until the last few years.

        • Pressure increases as bullet seating depth increases. This has been known forever and you can see that if you read a reloading manual that shows pressure data for the exact same load but at different case overall lengths due to different seating depths. It’s possible that “bullet setback” is a relatively new term to describe accidently-increased bullet seating depth, but conceptually it’s nothing new and, yes, its relationship to chamber pressure is proven a zillion times over.

          Keep in mind firearms are proofed to withstand pressures significantly higher than the caliber is designed for, just in case. It takes meaningful setback to get to the point where you’ve exceeded that large amount of fudge factor and have a kaboom type incident, and the degree to which it matters varies with caliber, powder used, projectile length, and more…

        • I think it was Capstick who wrote about a client using a big bore bolt safari rifle. When he was shooting, he kept reloading the internal magazine but never shot the bottom round. The recoil drove the heavy bullet deeper into the case. When he finally did shoot it, it was quite the explosion.

        • Yeah exactly, I’m hearing a lot of speculation and not a lot of citation. Anecdote is not the singular of data and all.

        • You were not satisfied with my response?

          Lapua loading manual in the safety section, data section, and other areas, contains gems like:

          You must absolutely follow the given cartridge overall
          lengths (C.O.L.) according to the reloading tables. The change
          in the bullet seating depth has a significant influence on the
          cartridge pressure.


          Caution: When loading handgun cartridges it is vital to maintain
          the minimum cartridge overall length (C.O.L.) listed in the
          tables. Shorter overall lengths may double chamber pressures.
          Longer lengths are permissible so long as the functioning of
          the handgun will not be impaired.

          And maybe we should just take a big step back and think about it from a very high-level physics perspective. It’s the very confinement of the powder that causes it to burn rapidly and with great pressure. Pour a pile of powder on the ground and light it on fire and it sparkles and fizzes and burns, but it doesn’t pop or explode. It’s only when you put that powder under pressure that is behaves nearly like an explosion (probably more accurate to say it deflagrates), and when you increase the pressure of that confinement you increase the speed and pressure of the explosion. See, for instance, notes from a Hogdon powder manual:

          When smokeless powder burns, a great deal of gas at high temperature is formed. If the powder is
          confined, this gas will create pressure in the surrounding structure. The rate of gas generation is such,
          however, that the pressure can be kept at a low level if sufficient space is available or if the gas can escape.
          In this respect smokeless powder differs from blasting agents or high explosives such as dynamite or
          blasting gelatin, although smokeless powder may contain chemical ingredients common to some of these
          High explosives such as dynamite are made to detonate, that is, to change from solid state to gaseous
          state with evolution of intense heat at such a rapid rate that shock waves are propagated through any
          medium in contact with them. Such shock waves exert pressure on anything they contact, and, as a matter
          of practical consideration, it is almost impossible to satisfactorily vent away the effects of a detonation
          involving any appreciable quantity of dynamite.
          Smokeless powder differs considerably in its burning characteristics from common “black powder.”
          Black powder burns essentially at the same rate out in the open (unconfined) as when in a gun.
          When ignited in an unconfined state, smokeless powder burns inefficiently with an orange-colored flame. It
          produces a considerable amount of light brown noxious smelling smoke. It leaves a residue of ash and
          partially burned powder. The flame is hot enough to cause severe burns.
          The opposite is true when it burns under pressure as in a cartridge fired in a gun. Then it produces very
          little smoke, a small glow, and leaves very little or no residue. The burning rate of smokeless powder
          increases with increased pressure.
          If burning smokeless powder is confined, gas pressure will rise and eventually can cause the container to
          burst. Under such circumstances, the bursting of a strong container creates effects similar to an explosion

          I mean…I just don’t know what else to say. The relationship between bullet seating depth and powder compression with chamber pressure has been known forever and is apparent if you’ve ever burned black powder or smokeless powder or whatever. It doesn’t do much of anything unless you confine it. And the tighter you pack it and the harder you confine it, the more explosive it is. …as a dude who used to be a kid who used to make black powder bombs, i can tell you that the tighter you wrap that ziplock full of black powder with the rocket engine igniter in the middle and the more layers of duct tape you wrap it with, the bigger the boom when you push the button.

        • Depending on the cartridge/case/primer/powder/bullet combination, pressures can skyrocket with minor load compression, or even a simple component change. As someone else stated, there’s a lesson for reloaders here. While properly documented and scrutinized compressed loads are not inherently wrong or dangerous, it’s absolutely possible to create loads beyond acceptable limits if the load is not worked up properly.

          Using the same load data from civilian equivalent cartridges in military cases without the proper workup process can produce unintended pressures. Loads that push pressures beyond acceptable limits create case splits, ruptures, primer pocket failures and the like. Loading oversights in a high quality bolt action rifle may mean hammering the bolt open, or a ruined rifle at the worst (assuming eye protection). With a pistol, the potential for destroying the firearm and serious damage to your hand is very high. If you reload, be meticulous.

        • Saw a guy shooting T/C Contender that was belching a good 3 foot of visible flame (in daylight no less) & asked him what hell was that. Said it was a .357 Magnum with his own handloads that he packed as much powder in the case that he could & compressed it seating the bullet. Any revolver except for maybe a Ruger would have detonated all over the range. Fortunately this guy quit shooting & said that his idea was a terrible mistake. I hope he disassembled the loads; imagine firing them in a SW & have parts flying everywhere.

        • I was hoping for actual cases of it causing a kaboom, or at least a definitive citation of it being a “known cause of kabooms” but all I see here is references to reloading material and even more speculation. I understand the theory FFS.

        • This is literally a documented instance of bullet setback causing a kaboom. Can bullet setback more than double chamber pressure? Yes. That’s been known since the beginning of ammunition loading and is also readily apparent by simply understanding how typical gunpowder behaves. Can this sort of increase in pressure cause a gun to blow up? Yes. Of course it can. …And it just did. My ammo was inspected and found to be correct in every way except for a couple sloppy loose bullets that took almost no effort at all to push down into the case. There’s no way that didn’t happen when the round chambered. It is what caused my gun to explode.

          I seriously do not understand the push back on this. What possible reason on earth could you have to not believe that bullet setback can cause increases in chamber pressure when everything that has ever been written about loading ammunition and the physical behavior of gunpowder in general shows otherwise? What could possibly satisfy you as a “documented instance” if you’re willing to overlook more than a century of knowledge and this very documented instance right here in this article where most other possible causes were confidently ruled out and the manufacturer of the ammo said (and demonstrated for me) “yep, our bad, the bullet wasn’t tight in the case and it got pushed down into it causing a pressure spike.”

        • ‘Any revolver except for maybe a Ru ger would have detonated all over the range.’

          Hmmm… It seems to me in Jeremy S’s case that the rear of the case ruptured sending pressure down into the maga zine well. This could not happen in a revolver since there is no maga zine well. It also seems unlikely that bul let setback would be a problem with a revolver, in fact the opposite, the bul let can slip forward under recoil potentially sticking out far enough to lock up the action. In a revolver the back of the case is fully supported, so it would likely take a much higher pressure spike than partially unsupported pistol barrel. And if a revolver goes kaboom, it seems like the shooter’s hands are down and out of the way of the shrapnel.

        • This situation was in reference to people improperly handloading. I have seen the back end of casings blow off in revolvers & hit the shooter’s hands. Also in the case of hot loads with weak cylinders & frames the whole top blow out of a revolver.

        • I can see the top strap breaking, but looking at a GP 100 I can’t see how the back of the casing could possibly blow off and strike the shooter’s hand. Of course not all revolvers are built like the GP. You’d have a hard time blowing one of them up if you were deliberately trying to. I’d think that the most likely thing would be the top of the cylinder breaking apart and the pieces flying off to the sides.

        • Not all revolvers are built like Rugers, have not seen failures with them. There has been a lot of junk built in the past that should probably be melted down.

        • My carry gun stays chambered. It goes into its quick-access safe that way when I go to bed (in the holster…the whole thing as a unit just comes off my belt and goes in the safe, then back on the belt in the morning). But many people carry a gun chambered then choose to unload it when putting it in the safe. They may literally chamber then eject the same round every day. Unloading the gun before putting it in a safe or on the nightstand or whatever is a personal decision and I make no judgement whatsoever on what people choose to do for their unique circumstance. However, chambering the same round repeatedly is not ideal and careful attention needs to be paid to how deep that bullet is seated in the case vs. how deep it’s supposed to be seated.

        • I do this but I rotate the round I do it with and after awhile I check them all with a caliper and reject those that have moved a measurable amount.

          Why? Because at night I screw a suppressor on to my daily carry gun before setting it on my bedside table and I’m not doing that with one in the pipe.

  5. Pretty awesome that they took care of you so well. Many companies are just about impossible to contact these days and will generally avoid taking responsibility.

  6. Glad your hand is still intact. Glad we all get to learn from it. You may have altered my range habits with this piece.

    I think this is a cautionary tale not just about the risk of defective ammo from the manufacturer, but about what could potentially happen if the same round gets cycled through a semi-auto too many times in the course of loading and unloading the same old carry ammo between practice sessions with target ammo, or just out of daily routine. Hitting that feed ramp one too many times could cause bullet setback and a similar scenario.

    • I keep dedicated practice mags to avoid unloading & reloading the same ammo. I also believe that modern polymer materials, when used in right application, are often superior to an all metal structure. Case in point is when the camera manufacturers went from metal bodies to polymer; if you dropped a metal bodied camera serious damage would occur; the plastic ones would usually just shrug off the impact or need significantly less repair. This could very well have been much worse with an all metal chassis. Maybe ‘Mythbusters’ could do a segment on blowing up handguns of varying materials.

      • Good points, but I wasn’t thinking of loading/unloading mags so much as the one-in-the pipe, assuming you carry with one in the chamber. Let’s say you eject that chambered hollowpoint and set it aside at practice time to shoot FMJ. Or when you unload for some other reason. Then when it’s carry time again you could either put that previously-ejected hollowpoint round back in the chamber, or somewhere in your carry mag (hopefully at the bottom), or back into a box of extras to be replaced with a fresh one. How you rotate that round with the rest of your carry ammo, and how often you load/unload will determine how quickly you might end up with a compromised round in the chamber. I’ve read some posts on the web where guys claim to have chambered the same round as few as two times before bullet setback was measurable.

    • This is exactly why I tell my friends and family to always keep their carry magazine loaded with carry ammo only. I just keep that one aside while at the range and put it back in when I’m leaving. Also another good practice to get into is purchasing ammo in boxes that have the seperators in them. This I always do for the reason of every new box opened I can see that all the ammo in that box is of equal height. If one or more round is short in size then those never get fired. Also save all your plastic dividers for when u buy bulk that comes in a box you can put your bulk rounds in them to visually look for abnormaly different length rounds and discard them accordingly.

    • Eh, it seems like there are already so many more ways to screw yourself with a hand load that this wouldn’t even move the needle…

    • And just what lesson would that be?

      If this was caused by an undersized bullet, then it wouldn’t matter if it was hand loaded or factory loaded. Kaboom, either way.

      A hand loader using a single stage press might be able to detect a different “feel” in the lever during bullet seating and/or crimping. Maybe, maybe not.

      • I think he’s just reminding us to be careful about making mistakes when reloading. As you noted, it’s clear the manufacturer made a significant mistake here and there was no way to anticipate it. If they loaded a bad round, or if I did, it’s BOOM either way. But, if a reliable ammo manufacturer can make that kind of mistake, we aren’t above a similar failure. Situations like this should remind us all to be thorough, careful and meticulous when loading our own ammo, or we could do the same damage – or worse.

    • I was a big reloader ’68-’90, every time I reloaded for a semi, I was dissatisfied. Locked up a revolver once, not enough crimp on a hot .357 load, bullet creep did not allow the last round to rotate into position. Bolt action or revolver strikes me as prime territory for reloading. Semis, not so much.

  7. I’d love to see an article on bullet setback – the risks, and how far back the bullet has to be to cause damage.

    I’ve come across a few rounds that are too far back over the years. Usually Freedom Munitions, maybe Geco once. Never knowingly fired any of them.

    • I’ve seen a few tests here and there. Sometimes it makes a big difference in pressures, sometimes not so much. I think some calibers are more susceptible…among other factors.

  8. Underwood made ammo that blew up in my hands.

    I continue to trust Underwood to make ammo that won’t blow up in my hands.

    • The only way to avoid the possibility of an ammo-caused incident like this is to never shoot. Google whatever decently-size ammo manufacturer you want (a starting point suggestion would be manufacturer name followed by the word kaboom) and you’ll scratch the surface of seeing that it has happened to all of them. I do trust that it’s no more likely to happen with Underwood than any other manufacturer. From previous chronograph testing I know how consistently they’ve always loaded their ammo and I believe them to be a solid, high-quality, precise outfit. In this case it was the projectile, made by somebody else, that was out of spec. Underwood is purchasing new inspection equipment to now double-check and verify the work of the projectile manufacturers before they load the bullets. Maybe they should have taken this step prior to my incident here and maybe not, but with it going into place now I trust the brand even more.

      Again, if you want to avoid this risk you’ll have to quit shooting firearms. If you think you can stick to Winchester or Remington or Hornady or whoever the heck ever isn’t Underwood and therefore be safe, you’re incorrect.

      • Apparently, the blame is all on Lehigh for the undersized projectiles. My experience with Lehigh is altogether positive, and in fact I am not real certain how solid copper, molded/machined bullets could be “undersized” all of a sudden, unless, for example, 9mm (.355) projectiles were provided to those who ordered .357 projectiles, or such. Some scary shit, here.

        • Agreed, I’m curious how Lehigh let those leave the factory in the fist place.

          At the least, I hope they will take a hard look at their QC protocols. Also, it makes me wonder how many more of those are ‘in the wild’, so to speak…

  9. This is what a well-documented failure looks like. While I’m sure your hand was stinging like a sumbitch, kudos on how you handled it, and then how thorough you were in documenting this, Jeremy. I’m glad to see that you shouldn’t suffer any permanent injury.

    This is a cautionary tale for people who like to shoot handgun rounds with big cases. Big cases + fast powder = opportunity for pressure excursions beyond 60K PSI. This level of pressure could test even some rifle actions to failure (eg, for you folks shooting handgun rounds in rifles and carbines – like lever-action carbines…).

    • No permanent damage. Even the incontinence has stopped 😉

      I wish I could have found the case, but am extremely confident in the findings of what caused this without it. It could likely be proven even further were I to dig the projectile out of that IIIA armor plate, but I don’t believe it’s necessary since other rounds in the box were found to have undersized diameters and were very easily pressed down into their properly-crimped cases. I was lucky in that 1) I was still able to test the gun for proper function (not firing out of battery) and 2) I caught the previous shot on film and could verify from the video that there was no bore obstruction (being dorky, I actually blew in the locked-back action to blow smoke out the attached suppressor). With those two potential causes crossed off the list and a barrel that had been proven to function through hundreds of rounds (including with various loads from Underwood), it really didn’t leave much else aside from the ammo being the cause. I can’t say how Underwood would have reacted had I not known what I knew and been able to present that case to them, but I can say that I couldn’t be happier in any way with how easy they made the process and how friendly they were about it. No defensiveness, no ego crap, etc. Just helpful.

      • Pulling the slug out of that test plate and measuring it’s diameter won’t give you an accurate measurement.

        Copper is malleable, the act of it just hitting the plate will shorten it a bit, and expand it a bit…

      • ‘…other rounds in the box were found to have undersized diameters…’

        If that’s the case, Underwood needs to issue a recall.

  10. Thats awesome customer service. I had a minor KABOOM in my M&P 40, just needed a new extractor and britches. I was shootng Freedom Munitions and they were less then helpfull, after some bitching i was able to return what I had left.

  11. The best way to prevent these mishaps is to shoot cartridges that have a rimmed case and a bullet with a deep cannelure/crimp groove. Hmmm…might be time for a 38/357 revolver.

    • When I reloaded +P .45 ACP loads (bullseye powder) for my 1911 I used hard cast gas check slugs with a tool that rolled a crimp in the case just below the bullet base… the system was total proof against bullet set back but it was fiddly extra step after the completed (standard crimp applied by my Dillon 650 progressive press)round came out of my progressive. and I don’t know if the rolling tool is made by anyone I bought it from a retiring gunsmith many years ago and I think he said he made it himself (rather beautifully with color case hardening on the polished parts and a black wrinkle paint finish on the base which is made of steel silver soldered together) from an idea he got from a Brownells catalog… all I can say it does work and it also reduces case life if you overdo it.

    • Years ago, I heard a tale of a ka-boom from another gunsmith. The circumstances went like so:

      – Shooter had a lever action rifle in .357
      – Shooter was hand-loading
      – Shooter decided that because he was shooting “light loads,” he didn’t have to crimp into the cannelure.

      I’m sure people who have reloaded can see this one coming. The rounds in the tube magazine, under recoil, bashed a pill pretty far back into the case. Bad things happened, and fortunately the injuries to the shooter were minor.

      There’s plenty of ammo for 5.56/.223 that’s loaded with cannelure bullets and crimped to prevent bullet set-back. Roll crimps serve a very specific purpose in higher recoil rounds.

  12. Good your OK. I’ve only been at this shooting thing for about 6years but why does GLOCK get the benefit of the doubt? If this was a lowly Taurus a chorus would say “see-Taurus is junk”! No I’m not defending Taurus(just put a Ruger 9E on layaway). How old was the gen3 anyway?

    • There’s no “benefit of the doubt” going on. The cause of this was diagnosed with extremely high confidence and it had nothing to do with the firearm at all.

  13. Even before reading the article, when I saw the area of the lower the Glock lower that failed I suspected a hot load or over pressure ammo issue. Years ago the only failure of a Sig pistol lower I ever encountered was the right portion of a P220 locking insert that broke loose and locked up the pistol making it unbelievably difficult to separate the slide from the frame. The cause of that broken P220 locking insert remained a mystery for years until the shooter finally fessed up to trying out a box of unauthorized 45 ACP +P+ rounds someone had given him.

    Although Underwood’s undersized Lehigh projectile diagnosis seems plausible, an isolated anomalous double powder charge in a single round that caused the Kaboom would be impossible to diagnose if it was the lone double charged round in a box, case, or lot of ammunition. Underwood Ammo has gained notoriety and is in demand because they sell ammunition loaded on the high side right up to the line of maximum, which is fine as long as EVERY SINGLE round of ammunition that leaves their factory is as close to perfect as humanly possible. Either way it all boils down to a quality control lapse by Underwood, Lehigh, or both, and might have something to do with record demand pushing the companies to turn out more product faster.

    There are reasons why all the major ammunition manufacturers in the U.S. have become increasingly conservative over the last 4 decades and no longer offer real full house “hot loads” which created an opportunity for the niche market Underwood services. The two most obvious reasons why Federal, Winchester, Remington, Speer and other major players no longer manufacture hot loads are the minimal margin for error and unacceptable product liability exposure.

    • They showed me proof that other projectiles in the box were undersized. While it could have been my fault, the bullet also impacted meaningfully off from where I was aiming, which was a surprise to me as I felt the shot was good and I’m typically quite accurate with this gun/barrel/sights setup (this accuracy issue can be explained both by the bullet starting from low in the case and having to jump a farther distance to the rifling and by an undersized round not contacting the rifling as well as it should have). I personally have high confidence in the diagnosis for these two reasons.

      BTW all of the other brands you mentioned do manufacture +P high pressure ammo, and in some cases even in calibers where “+P” isn’t an official SAAMI thing. They all produce significantly larger volume than a small-ish company like Underwood and generally cannot be as consistent because of it. Outside of expensive match-quality ammo from those brands (e.g. Federal Gold Medal) you’ll find higher standard deviations in velocity than you will with Underwood, of which I’ve chronographed quite a bit and always found it to be very consistent.

      BTW #2: there are ways to achieve high velocity without getting into pressures that exceed SAAMI spec (mostly it’s about powder science and controlling burn/expansion rates), and many or even most of Underwood’s loads are within normal SAAMI spec and not even +P. Their brand is about pushing velocities and therefore energy levels beyond the norm, not about pushing pressure levels beyond the norm.

      • Jeremy you’re missing the point I’m making about the major ammo manufacturers becoming more conservative over the years, sure they all offer +P loads in various calibers, but even their +P offerings aren’t loaded on the high side muzzle velocities and maximum chamber pressures. Underwood ammo muzzle velocities are significantly higher than comparable offerings from the big four I named.

        A good example is the legendary Speer Gold Dot 357 Sig 125gr GDHP round which when it hit the market over 20 years ago had an advertised muzzle velocity by Speer of a sizzling 1420fps, but within a few short years Speer dialed that velocity back to 1350fps which is where it remains today, in other words, Speer became more conservative and no longer offers a hot load 357 Sig 125gr GDHP. Underwood Ammo however, manufactures 357 Sig ammunition using that same Speer 125gr GDHP with an advertized muzzle velocity of 1475fps, that definitely qualifies as a hot load; and so does most of the other popular ammo Underwood offers.

        All of the major ammunition manufacturers have become more conservative over the years which has resulted in dialed back muzzle velocities, if they hadn’t Underwood wouldn’t be in business and able sell their higher priced “hot loads” as fast as they can turn the ammo out. It’s not complicated, Underwood is supplying max load ammunition with muzzle velocities Federal, Winchester, Remington, and Speer will not produce.

        • You think Speer’s load changed or their published chronograph data changed? It used to be pretty dang common for manufacturer-stated velocities to be way optimistic, flat-out lies, or honest results but from non-standard barrel lengths. This has changed a lot as information became available on the internet instead of just through gun magazines repeating manufacturer claims, and chronographs became more commonplace in the consumer market. Manufacturer velocity claims tend to be pretty reliable now, but that really wasn’t the case in the not-very-distant past.

          Plenty of major manufacturers in the last couple of years have released new products with uniquely high velocity as their primary selling point. Examples would be the entire Hornady Superformance line (“100 to 200 fps FASTER than any conventional ammunition on the market today”), CCI’s COPPER-22, A17 Mag, and A22 rounds, Remington’s Nitro-Steel, Ruger’s ARX loads, most of Winchester’s Varmint-X line, plus entire new calibers to the market like .17 Winchester Super Magnum (fastest rimfire ever) or 6.5-300 Weatherby Magnum (fastest 6.5 ever) or most of Nosler’s recent offerings. And Armscor .22 TCM and Aguila trying to reignite the 5mm Rem Mag thing, if you consider those brands to be major manufacturers (they’re certainly making way more ammo than Underwood). …I’m sure many others…

          All this said, I agree with you that the margin for error should something like bullet setback happen is probably tighter on a product like Underwood’s. But I’d caution against simply assuming that uniquely high velocities necessarily equate to high pressures. Again, most of Underwood’s loads are standard-pressure loads. And I’m really not sure you can convince me major manufacturers refuse to push the pressure envelope when some even sell +P+ ammo (e.g. Federal, Winchester, etc).

        • Jeremy I’m not sure if you’re that misinformed or just embarrassingly hard headed, but either way you’re wrong. When Texas DPS transitioned to the P226 & P229 in 357 Sig during the late 90’s, the Speer Gold Dot 125gr GDHP was thoroughly tested and evaluated which included chronographing the ammo which verified the 1420 DPS muzzle velocity average. Speer dialed back that Gold Dot round to1350fps, that’s a fact whether you want to believe it or not. You should educate yourself and learn why there is no such thing as SAAMI specs for any +P+ ammunition, why the use of +P+ ammo will void the warranty of many firearms, and why most of the very few LE agencies that opted for 9mm +P+ duty ammo have dropped it due to poor ballistic gel testing results that exposed problems with over penetration and unreliable expansion along with the voided warranty concerns. Federal HST 9mm in both standard and +P 124gr or 147gr is a perfect example of how advancements in bullet design and construction offer ideal and consistent penetration and expansion, and even the HST +P in no way form or fashion could be considered a hot load. By the way, other than scenarios such as bear attacks, a Glock 20 with hot loads is a really poor choice for personal defense.

        • Hard headed.

          I’m responding to you stating that “all the major ammunition manufacturers in the U.S. have become increasingly conservative over the last 4 decades and no longer offer real full house “hot loads”, which I just don’t see as being true. I listed various examples that sprang to mind of major manufacturers in just the past two-ish years releasing some of the hottest rounds on the market and even designing new calibers to push the velocity envelope further. Gel test merits of +P+ ammo aside, Federal, Winchester, and others still manufacture “+P+.” While SAAMI doesn’t officially define what +P+ means, for the calibers that have an official +P rating it’s usually 9% to 10% over standard pressure and the message from the manufacturers that sell “+P+” is that this designates a load that exceeds 10% over standard SAAMI pressure. Wink-and-nod definition or not, “no longer offer hot loads” just doesn’t hold up with all of these examples of currently-offered hot loads. It also isn’t even relevant to my Glock here, as this load from Underwood is apparently not +P. And it strikes me as odd to say that +P Federal HST isn’t a hot load, as it is by strict definition. Again, I’ll remind that velocity and pressure do not always share a direct correlation. If Federal says it’s +P that means it’s over standard SAAMI pressure (likely 10% over) no matter what velocity it’s making.

          I’m more than happy to grant you your Speer .357 SIG example as an instance of a manufacturer reducing the power of a load. I’ll also volunteer that most manufacturers of 10mm followed the “FBI load” example and haven’t made full-power 10mm since then. But are all of the currently/still-offered and even brand new hot loads I mentioned from Hornady, Federal, CCI, Winchester, Remington, Weatherby, Ruger, etc as examples irrelevant?

          And funny you should mention it, as I literally do carry my G20 specifically for bears, with 220 grain hard cast lead rounds. My EDC carry load is 9mm Federal HST 147 grain standard pressure.

        • Well Jeremy, the suggestion all ammunition designated +P by the manufacturer is automatically considered a “hot load” is absolutely ridiculous. Anyone who’s done much shooting knows there’s quite a noticeable difference when firing hot ammo compared to most factory standard and +P ammunition. There’s a reason why no 357 Sig or 10mm Auto ammo is designated as +P even though most duty or defensive ammo in those calibers tend to be noticeably hot when fired. Both terms are somewhat relative, but no honest evaluation of Federal 9mm HST +P 124gr or 147gr would rate that ammunition as “hot” by any stretch. What the relative term “hot load” generally means to most experienced shooters is ammunition loaded right up to or slightly below the maximum safe powder charge for the sole purpose of increasing the muzzle velocity and muzzle energy.

        • Typo correction: There’s a reason why no 357 Sig or 10mm Auto ammo ISN’T designated as +P even though most duty or defensive ammo in those calibers tend to be noticeably hot when fired.

        • Fair enough, Ted. If you define “hot” as particularly fast or powerful for a given caliber that’s totally valid (and may have nothing to do with pressure level, which is fine). I suppose because of the context of the kaboom here I’m primarily defining “hot” as high-pressure (which is also a valid definition of the colloquial term “hot load”). Is 9mm HST +P a “hot” round from a performance perspective? That’s somewhat subjective and if you believe it isn’t then I’ll go along with it. Is it “hot” in that it’s over standard pressure? Yes, it is. …maybe crossing paths on definitions here is the largest source of our continuing debate haha… (although I do think I gave many strong examples of very “hot” as in uniquely fast/powerful loads being currently sold and continually developed by major US manufacturers so would again remind that I can’t agree that no major manufacturer makes “hot” loads anymore)

          As I’m sure you know (but I’ll put it here because it’s a common question and some people might be foolish enough to actually read 5 posts down in our back-and-forth conversation here haha), “+P” in 9mm has a very specific SAAMI definition and it means it’s 10% over standard pressure. SAAMI only defines a +P load rating for 9mm, .38 special, .38 auto, .45 ACP, and some random rifle caliber (edit: .257 Roberts). Other calibers do not have an approved/official SAAMI +P load level and therefore if you see a “+P” designation on them it’s just a slightly loosey goosey term used by manufacturers to denote that the load exceeds the SAAMI approved pressure for the caliber (and “+P+” is when the load exceeds a SAAMI-defined +P pressure level). Underwood does choose to designate loads as +P that exceed SAAMI pressure specs even in calibers that do not have a SAAMI-official +P specification (e.g. .380, .32, .44 mag, etc). It is my understanding that, while the 10mm load in question in this article is most definitely, absolutely “hot” by your definition of making a high power level for the caliber, it is not “hot” in that it exceeds the approved SAAMI pressure for the caliber.

          If you’re concerned about margin of error for safety should something like bullet setback happen, pressure is a huge data point. Pressure can be independent of velocity, power level, and especially felt recoil. High pressure/low pressure does not correlate to felt recoil very well at all. Most reloading manuals specifically mention this in the safety section as they want reloaders to be sure to not rely on felt recoil to determine when they’re reaching dangerous pressures. Likewise, it would be unreliable to look at two loads that use different powder but are otherwise identical and assume that the one pushing the bullet faster is the higher pressure load. That simply isn’t always the case.

          …if you so choose, you may close this discussion out with a final comment. I think we’re at the point where we’ll continue repeating ourselves and don’t get anywhere further, so I shall bow out. I appreciate the discussion and hope you don’t think I’m a complete jackass (49% jackass is acceptable).

  14. I’m glad the shooter is ok and remembered to wear glasses. I need to get better about that habbit.

    I’m also happy Underwood took ownership of this problem. I am curious if they knew Jeremy did reviews and gave him special treatment? Again I’m glad he’s ok but I’m curious.

    • I don’t feel that I got special treatment. Considering they could have easily kicked this can to the projectile manufacturer but wouldn’t even hear of it (I literally suggested it after they diagnosed what happened, and their stance was basically “it’s our ammo, end of story”), I’m inclined to believe they’d stand behind their product for anybody. If anything made the process easier for me than it might have been otherwise, I think it was the fact that my initial communication to them included what I thought was pretty clear evidence that the gun did not fire out of battery and that there was no bore obstruction. With those two potential causes extremely unlikely at that point, I wasn’t asked to go through any further diagnostic tests or a Q&A session or whatever, and Underwood’s first response was telling me how they were going to take care of me and sending a return label for the rest of the ammo, etc etc. Very friendly tone from the get-go.

      • Actually, it sounds like we’re all getting “the special treatment”. They told you:

        “The issue has been resolved and we have invested in the most advanced inspection equipment available to ensure nothing like this will become an issue in the future. This equipment utilizes infrared laser technology to detect any inconsistencies in the rounds or projectiles. It is able to do so with far more scrutiny and accuracy than any other method we have come across.”

        So, you showed them a lot of problem ammo, and they “resolved” the problem with the application of some high-tech QC equipment. These types of solutions take time to implement. You don’t just punch 800.741.0015 into your cell phone, and have a Brownells Signature Series laser bullet inspector show up at your door the next day. You have to research solutions, wait for quotes and demos, cut the check, wait for your new equipment to be made and delivered, and their factory rep come out to train up your staff on it.

        The ammunition manufacturer did not, as they made it sound, inspect your box of ammo, implement this new QC process, and then respond to your letter the next day.

        If this was a recently manufactured box of ammo, how did they get the “solution” all set up so quickly?

        If this was a box of ammo that hung out in the supply chain for a while before it made it to your stash, why didn’t it get pulled back from retailers?

        Either way, where is the recall on all the ammo they made before they unleashed the QC robots?

        You appear to be giving them a pass, without asking the obvious, basic questions about their response.

        • My impression is that they already have this equipment for inspecting loaded rounds, which is something I’ve seen at other ammo manufacturers, and they’re going to add another one dedicated to inspecting projectiles prior to loading.

          I did receive a follow-up statement from them RE the idea of a recall, and added that to the bottom of the article.

  15. Polymer sucks. It’s cheap garbage. I had an all steel Russian Makarov kaboom in my hand once due to a barrel obstruction. It was amazing. The steel slide popped off the top of the steel frame. Which makes no sense unless the metal stretched and flexed to allow it to happen. The ammo flew out the bottom of the magazine which again stretched and flexed to allow the steel magazine floorplate to pop off the steel magazine body. Pieces of the gun went all over the place. Amazingly – I was uninjured. I inspected the pieces. Reassembled the entire gun right then and there. Noted the barrel bulge in the barrel, switched ammo, loaded up some sellier and bellot ball, and finished out the box with no problems. The gun survived and I was uninjured. That wouldn’t have happened with polymer garbage.

      • Fixed barrel, blowback design. Really not necessary. There is no lockup. But it’s good to know you NDE experts are combing through here letting people know who is and who is not “idiots” based on your vast UT experience.

        By the way, I’ll take your lack of refutation regarding the tensile strength of polymer vs steel as a conceding of the point.

        • Hmmm… you mention tensile strength… exactly what are you referring to? Yield strength? Proportional limit (ie elastic-plastic transition)? Ultimate tensile strength? Fracture stress? And that completely ignores the MUCH more significant and relevant discussion of mechanical fracture toughness and total absorbed energy to failure. Looking at a single point on a epsilon/sigma curve (even if you specified which specific point you mean by the vague term “tensile strength”) provides very limited information about one specific material property in isolation. Try integrating the whole area under that curve and you’ll get a much more holistic view of the actual issue under consideration here, namely a materials ability to absorb energy without fracture.

        • RocketScientist. In what universe can your integration result in glock polymer exceeding the strength of steel for the situation presented? You guys are cracking me up.

        • Oh jesus christ. You’re missing my entire point that simply pointing to one property (“strength”, which you still haven’t actually specified what you mean by that) is a fools errand. I could show you a dozen different materials with a higher “strength” than steel, that would make TERRIBLE firearm frames (as in, completely unusable and most likely extremely unsafe). Because its not only about “strength”. Isolating “strength” as the end-all be-all metric for assessing suitability of a material is like looking at one number on a vehicle’s spec sheet and assessing its suitability as a pickup truck based solely on that. Oh its got a longer bed than the other options, must be the best! Nevermind that it only has a 90hp 4-cylinder,a towing capacity of 800 pounds and no power steering, this is CLEARLY the best truck since it has a longer bed! If you want to have an actual discussion, spend like 20 minutes googling “mechanical toughness” and get back to me with an explanation of (a) which material property you refer to when you specify “strength” and (b) why that is a more suitable metric than toughness, stress at proportional limit and area of elastic regime in an epsilon/sigma curve.

        • Haha. No, you are missing my entire point. In what universe is a glock polymer frame going to withstand more pressure before breaking (like the situation in question) than steel? You’re the rocket scientist, pick a point on your curve where “glock polymer” is better. Show me. Then tell me how in this instance (the gun blowing up) glock polymer is superior. Show me. Please do. I want you to stop beating around the bush and show me. Do it now. I want you to prove me otherwise. Do it. Look it up in your “strength of materials” book and give me facts. Make it happen. Now. Do it.

        • “pick a point on your curve where “glock polymer” is better”

          Well, thanks for clearly confirming you have a very limited understanding of the principles at play (and not-so-great reading comprehension as well). The whole point is you can’t just pick a “single point” on a curve and declare something a winner. How about this… ASTM A339 nodular cast iron has a MUCH higher Ultimate Tensile Strength (I’m assuming that’s what you meant with the vague term “strength”) than stainless steel alloys. So picking that single point on the curve (as you requested), it is FAR superior to stainless steel as a material for firearms frames…. right?

        • @RocketScience

          I award you the score of F.

          The topic of discussion is not my understanding of your “principles at play” or how fantastic A339 is in regard to ultimate tensile strength. I asked for information regarding “glock polymer” and you bring up A339 and compare it to… ? Stainless steel??? Lets recap:

          The questions asked:
          ** In what universe is a glock polymer frame going to withstand more pressure before breaking (like the situation in question) than steel?

          ** Then tell me how in this instance (the gun blowing up) glock polymer is superior.

          These have been the questions from the start. Jeremy’s gun is a glock made of polymer. Not Stainless steel. Not A339. And you accuse me of having a problem with reading comprehension?

          I would like you to prove me wrong, so I can feel better about being wrong about manufacturers making firearms out of quality, durable materials with exceptional material characteristics in regards to the last generation of materials (steel), rather than forming them out of a material reminiscent of cheap garden tools.

          Still waiting.

        • All the arguing happening above aside, I agree that a steel frame would have likely shrugged it off. For instance, were I shooting my CZ SP-01 or the 1911 in my safe or whatever. But as pointed out earlier, basically all of these pistols have screw-on grip panels made of plastic, wood, or some composite like G10. As Dyspeptic Gunsmith pointed out, serious overcharges in these pistols often cause the pressure to blow out the grip panels and can fill hands with shrapnel and wood splinters and such. Given the choice between the frame blowing up at the top (seems like this area around the locking lug pins is the clear weak spot in the Glock frame, and nearly every single KB has this part popped out just like mine) or grip panels blowing out right underneath my hands, I’ll sacrifice the gun every time. I could care less if my $275 frame survived unscathed if it meant my hands took the damage instead.

          Yes, clearly this did not happen in your Mak KB incident. Sounds like the most ideal thing possible happened, where the pressure actually shot down and out the bottom of the magazine and didn’t blow the grip panels out. That’s freaking awesome! But it doesn’t always go that way. I’m not sure I’ve ever seen a Mak KB…straight blowback actions can have advantages. It’s a stout gun and a low-pressure round, so likely quite safe. I’ve seen a Tokarev KB where it blew out the side of the steel slide and blew the left grip panel off. Plenty of shattered grips on SIGs and other metal-framed guns with grip panels, too…

  16. I’m guessing that stings just about as badly as holding an Altoids tin shut when a black-cat goes off in it.

    A friend of mine did that. Made a really cool looking tin.

  17. Yikes!

    If you havent already I would get that barrel examined for micro fractures (they soak it in a UV reactive dye and put it under a blacklight) before/if you plan to shoot with it again.

    There is a video floating around on Youtube where a guy had a KB with a 40S&W Glock (think it was a G27), it looked just like yours, fit in the slide, worked when manipulating the slide, and rounds chambered without any glaring issues. He put it under the blacklight after the V dye was applied though and the whole chamber mouth looked like a broken pane of tempered glass, spider cracks going everywhere, definitely NOT something you would want to shoot with again.

    • It’s called wet magnetic particle inspection. They soak it in medium that reacts magnetically and glows under ultraviolet light. They magnetize the material with a mag gun and the particulates align to a disrupture in the magnetic field (like a fracture). This allows them to see fractures within the metal under UV light while it is magnetized.

  18. Wow! As a Non- Firearms owner I guess all those videos on YouTube of various semi-auto pistols going “KABOOM” within the past years is pretty serious…I’ve seen Glocks, S+W MP’s , Coonan’s, and a few Revolvers that turned into pipebombs! Maybe I’ll stick to just collecting cultery, swords and ancient arms….I’ve never seen a Bowie , wakizashi or Gladius explode !

    • Become a gun owner. Don’t let stuff like this scare you. Life is full of unknowns. I can die in my truck driving off a mountain but I’d die in a place I had good times at. Lol. I could get in a wreck. Maybe a airplane crash?

      If you add up the number of guns sold, ammunition made, and figure how many Kabooms happen with just gun and ammo makers as variables, I wouldn’t be surprised if that failure rate was really low. What happens in life will happen. Just do your part to be safe.

  19. Maybe it’s time to trade in those hand “grenade” pistols for something more reliable….Like a longbow, slingshot, Atal-atal, boomrang, a sling, javelin, etc…Those ancient arms never “exploded”!

  20. Articles like this imprint on me. I inspect my ammo very carefully before loading it in my firearm. I have even been thinking about weighing each round.

    • Weighing and visual inspection would not have helped. I would have had to press on the bullet or otherwise grab it and try to move it to ensure it was snug in the case. I’ve actually done that with .22 LR before as a QC check before shooting but never with a centerfire round.

    • @ Michael Wilson
      And out of the gazillions of rounds fired and used in the USA, how often do you hear of catastrophic weapon failure from a major commercial manufacturer of ammunition?
      That’s like not driving your Toyota because you heard floor mats get stuck on the peddles and cause the car to go off cliffs.

  21. Glad u werent hurt. Nice industry response. Excellent writeup and diagnosis. Controlled explosions arent always controlled….

  22. Jeremy, Great article! Glad you didn’t end up like Captain Hook… although that would be awesome. I would love to see more after action reports like this to help people deal with the “when things go south” with their guns.