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I keep exploring the Mech Tech Carbine Conversion Unit that Jeremy S. previously reviewed here. It’s a cleverly-designed “upper” that you snap your GLOCK pistol “lower” into, converting your wundergun into a 16″-barrel carbine rifle. This particular unit converts the GLOCK into a 10mm rifle. I previously evaluated the Mech Tech with some hollowpoint ammunition for its suitability and performance as a self-defense weapon. It was impressive, sure, but I couldn’t help but think that that was the wrong path to go trundling down. Sure, it could be used for that purpose, but the bullets were overdriven so fast that they were ripped apart when the hit the gel. And that got me thinking — what would this unit be like, using some big heavy solid hardcast bullets? . . .

Fortunately, in doing the chrono testing for Jeremy’s review, I had a couple of Underwood bullets left over. Jeremy had sent some 180-grain TMJ (a generally rounded-nose projectile but with a flat face, like most .40 and 10mm FMJ’s) and some 220-grain Underwood hardcast flat nose hunting bullets. And I had some DoubleTap 200-grain wide flat nose hard casts, too.

These are not expanding bullets. These are designed to penetrate and penetrate deeply, and the flat face of the bullet does more damage than a rounded nose would. Flat-faced hardcast bullets are used for taking down big game, where you need a bullet that can smash through heavy bone structures and penetrate deeply to the vitals of a larger animal.

Now, 10mm has been used for that purpose for quite a while, from guns such as the GLOCK 20 with its 4.6″ barrel. I was curious as to just how much performance we could get from this type of ammo when fired from a 16″ barrel. Accordingly, I strung four 16″ blocks of gel end-to-end; that gave me 64″ of tissue simulant to catch the bullets. Maybe that’d be enough, maybe not, but it’s as much as I could reasonably assemble, so — I set out to blast them.

First things first; these rounds were potent. They ranged from over 900 ft/lbs of energy, to over 1,023 ft/lbs. That’s a lot of power. And yes, they penetrated very deeply in the gel — the shortest bullet I tested was the wide flatnose DoubleTap 200gr, at 50″. The Underwood 180gr TMJ went 57″, and the Underwood 220gr flatnose penetrated over 64″! I don’t know how far it would have gone as it penetrated past the end of my string of gel blocks. There’s a clear exit point so I know it made it through the block, but I don’t know how far it would have gone in an endless gel block.

Needless to say, that was pretty impressive. Getting a thousand ft/lbs of energy from a semi-auto handgun round is no small feat, and the bullets performed admirably. All the tested ammo showed substantial gains over their rated velocity and the non-deforming nature of the solid bullets means that all that energy was to work — no disintegration or fragmenting, just a big, heavy, solid mass that was pushed harder than it likely ever was supposed to, and did exactly what they should have.

This Mech Tech CCU is becoming one of my favorite GLOCK mods, and if I ever am tasked with having to take down a large dangerous animal with a semi-auto handgun, well, now I know exactly what to use to give me the best chance.

I should note that Mech Tech advises against using any Underwood ammo in their carbine conversion units, saying that they’ve been notified of overpressure situations. Please don’t take my use of it here, or in the prior test, as an endorsement to ignore the manufacturer’s warnings. Jeremy had already used it successfully and inspected all cases for any signs of overpressure issues and found none. I used the same ammo that he had previously vetted and encountered no issues.

I don’t know what calibers Mech Tech encountered problems with, but these particular boxes of these particular loadings showed no issues, so he and I felt it was safe to use. But, we took that risk on our own, against the manufacturer’s advice, so … let’s just say that it’s usually a good idea to follow the manufacturer’s recommendations and advice. Or put another way, do what they say, not what we do, and all that.

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  1. Sweet! That Underwood 220 grain hard cast is what I carry in my G20SF as a woods load when picking Huckleberries in the Inland Northwest here, where the only folks who like the Hucks more than the residents are the resident bears — both black and grizzly flavors. Sometimes it’s the factory barrel, and sometimes it’s a 6.6″ Lone Wolf. Lots of folks think it isn’t sufficient, but 15+1 of a controllable round that can be shot rapidly on target and might actually make it nose to tail completely through a bear ain’t nothin’ to sneeze at.

    • Jeremy,

      That is certainly a fairly potent combination for bear defense. I have to wonder if you would get better stopping ability from a 180 grain hardcast lead bullet. Even though it would be lighter, it should allow for considerably more powder capacity in the casing and, hence, higher velocity. Velocity would be higher because of the lighter bullet as well. Rather than getting, say, 1150 fps with a 220 grain hardcast bullet, you might get something like 1350 fps with a 180 grain hardcast lead bullet.

      I am keenly interested in velocity because the higher the velocity, the greater the diameter of the permanent wound channel when you are shooting hardcast lead bullets with large, flat meplates. If you are interested, I can share a website with a wound channel estimator based upon bullet diameter and impact velocity.

      • It would be faster, but even the 6.6″ barrel is too short to burn all of the powder in the 220-grain loads anyway. A faster bullet would stay in the barrel for an even shorter time so less powder of the total powder would burn. I mean, I could shoot a 135 grain FMJ and see super high velocity, too. I certainly think you could be right and a HCL 180 grn might outperform the 220 grn in ability to stop a bear quickly in certain scenarios, but I decided to choose ultimate penetration capability over whatever the initial wound cavity might look like. Too many variables and it’s a lot of guess work, and I ultimately chose to go with the heaviest bullet out there.

        • Hmm, that is interesting that some of the powder is in tact even with a 220 grain bullet. The real questions then are what velocity would both bullets exhibit and would any increase in velocity produce any significant increase in the permanent wound channel. I suppose yet another question is whether even a significant increase in permanent wound channel would increase the stopping ability of the bullet.

          Like you said this is pretty much guess work. And as we all know ALL handguns are “under powered”.

          Speaking of “under powered” handguns, when handguns can launch bullets at velocities of 1400+ fps — which is on par with velocities of modest shotgun slugs — I like to think of those handgun/cartridge combinations as simply slower than shotguns. They can easily deliver the same amount of trauma as a shotgun slug … it just takes multiple rounds to do it. And it obviously takes longer to put five or six rounds on target than one slug. Hence I think of the most potent handgun/cartridge combinations as slower powered rather than under powered.

    • I thought Glocks weren’t perfectly happy with lead rounds due to their polygonal rifling…?

      • It’s considered fine as long as you make sure there’s no buildup happening. Leading of the barrel is what will eventually cause excessive pressures. Some of the gas-checked rounds prevent actual lead-to-barrel contact anyway, especially in polygonal rifling that doesn’t cut into the bullet like normal rifling. At any rate, this is one reason I got the Lone Wolf barrel. They use standard rifling so I don’t have to worry about hardcast lead. Plus that extra couple of inches appreciably bumps the velocity of 10mm.

      • My memory is that Glock’s warning concerned the octagonal rifling of the .45ACP models. If the hard-cast bullets you use are gas checked then you will not have the leading problem.

  2. Hey ShootingTheBull410,

    How large was the permanent wound channel from the hardcast lead bullets? I have been dying to see that result!!!!!

    • Unfortunately, the gel I had available for this test (ClearBallistics) doesn’t represent the permanent wound channel the same way as organic gel does. ClearBallistics is useful for general penetration and expansion characteristics, but it’s not well suited to accurately portraying the permanent wound cavity.

      You can check my .454 Casull hardcast test for an idea of what a hardcast bullet does to gel/tissue.

      • Thank you ShootingTheBull410 … the hardcast bullet actually exceeded my expectations. A 1.5 inch diameter permanent wound channel is going to halt all but the largest of beasts (e.g. whales, elephants, hippos, and rhinos).

        I don’t suppose you can tell me how large the permanent wound channel was near the end of the track at something like 40 inches of penetration?

  3. Those sweet, elegant, timeless lever guns that come in handgun calibers achieve improved ballistics as well.
    That being said;
    I guess this is natural evolution of things. I currently don’t own a G in 10mm, however, I do have my lovely railroad tie with grip G21. Any plans for a 45 upper? Any estimates on ballistics with this whiz bang upper? Thompson comes to mind.
    Similar to a Kriss without the Kriss bling?

    • Check out the link that STB410 provided to my Mech-Tech review. They make uppers for all Glock calibers except .45 GAP, and since all small frame frames (9mm, .40 S&W, .357 Sig, .45 GAP) are identical (well, the full-size ones, meaning G17, G22, etc) and the large frame frames are identical (10mm and .45 ACP, or G20 and G21) you can use any of the matching frame size Mech-Tech uppers with a single frame. In the video here, STB410 is using his G21 lower with the 10mm upper. If you have a G17, you could have uppers in 9mm, .40, and .357 Sig…

      As STB410 mentioned in the video, though, .45 ACP doesn’t actually gain very much velocity out of the longer barrel. It’s designed to burn all of its powder in a ~5″ barrel and it does a good job of that. Extend the barrel out to 16″ and you might gain 100 fps, but it’s nothing like the gains seen in 10mm. Same story (limited gains) with 9mm. .40 does a bit better, and I’m not sure about .357 Sig but ‘Ballistics By The Inch’ probably has data.

      • I beg to differ as to whether .45ACP gains velocity when shot out of the longer MT barrel. I do have and use one.

        The correct answer (consult Ballistics By the Inch etc.) is counter-intuitive: The light high-velocity .45 rounds (such as 165 grain CorBon DPX HV) gain much velocity fired from the 16-inch MT barrel. The heavy rounds (230 grain STD for example) either gain no velocity or actually lose a bit.

        The result flows from the greater powder volume in the 165 grain DPX cartridges, the more compact charge in the heavy bullet cartridges, and the greater friction of the heavier longer 230 grain bullets.

        It is these facts that caused me to lay in an MT in .45ACP, running on my G20 lower: It provides a very subsonic low muzzle flash- and -blast load with one magazine (good for indoor defense)…but a very high velocity/energy shot with the 165’s inserted.

        • This is true of pretty much all pistol cartridges in long barrels, not just .45. The lighter the bullet, the more powder (usually), and the more the velocity gain. If you get something ridiculously light and overpressured, like Liberty Defense G2 (to remind, it’s 50 grains, 2000 FPS from a handgun barrel), it speeds up all the way to 2500 FPS. Of course, lower weight also means that BC is worse, so they may start fast, but they’ll bleed that velocity off pretty fast, too.

      • I would note that given the slightly reduced velocity of the 230 grain .45ACP loads from the MT .45 upper….and the reduced muzzle blast in any case from the much longer barrel, the MT .45ACP (once you have it threaded) makes an excellent suppressor host…from the sound pressure level point of view.

  4. I bought a CCU in 9mm last year, mostly because if I was going to have a rifle that looked like an AR, I wanted a 33rnd mag to go with it. Frankly, I think I made a mistake; I should have gotten one for my G20.

    Those tests were phenomenal. I can hardly believe how well those rounds performed! I knew that out of all the handgun calibers, 10mm really gets a nice boost from the extra barrel length. I use Accurate #9 in my reloading,, which is a slower powder meant for magnum calibers, so I could probably get some real wallop out of a 16″ barrel with my reloads.

    • John P,

      I have never heard of anyone who has tried optimizing 10mm or .44 Magnum loads for 16 to 22 inch barrels. I have to wonder if some significant gains in velocity are possible over standard loads designed for 6 inch barrels.

      Personally, I think this is a seriously overlooked area for what could truly be the “perfect” self-defense firearm and ammunition combination. (I know, there is no such thing … humor me.) A carbine with a 16 inch barrel is great for maneuverability in close quarters combat. And yet you can expect acceptable accuracy out to at least 100 yards with iron sights and maybe to 200 yards with an optic. Finally, a 220 grain bullet in 10mm or .44 caliber with a muzzle velocity on the order of 2,000 fps would be devastating to any human attacker with proper bullet construction designed for higher velocities. The open question is whether optimized propellant would actually lead to muzzle velocities around 2,000 fps in 16 inch barrels.

      Oh, and I forgot to mention the big advantages of such a carbine over a shotgun: far greater ammunition capacity and much less recoil and muzzle blast without any significant sacrifice in stopping ability — especially at close ranges.

      • I’d like to shoot 600-grain, .458 SOCOM slugs at just under the speed of sound through an integrally-suppressed carbine. That right there would be my dream hunting (especially hogs within 100 yds) or even home defense firearm. Should be quiet enough to comfortably and safely shoot without ear pro, and be capable of taking down most any game (~1,460 ft-lbs with 600 grains doing 1,050 fps). Shoot a 250-grain load through it and you’ll make 2,565+ ft-lbs…

        I like the idea of subsonic .44 Magnum also, but you’re capped at like 330 grains and the rimmed cartridges don’t lend themselves to semi-auto use.

        IMHO, heavy projectile, subsonic, suppressed options are the next “thing,” and I think .458 SOCOM is going to hit its stride when suppressors and integrally-suppressed AR uppers become available in the chambering, along w/ heavy loads just under supersonic speeds…

        • Funny how the thinking on caliber has evolved over the decades from big/slow to fast/small – all the way to 6mm in rifles and 5.7 in pistols.

          Now with hearing conservation and penetration considerations indoors driving the thinking, we are cycling back to big/slow as the next thing. Hey, what about an air rifle in .50 …? Remember Lewis and Clark?

          One advantage to guys in gun-grab states that might buy the ATF cop killer thinking is pistol calibers are less likely to be banned or restricted.

        • I have put serious thought into that route as well … thinking along the lines of a heavy .50 caliber projectile with a muzzle velocity of 650 feet per second at the muzzle for home defense. A hole that big doesn’t need any expansion to be effective. And I was hoping the slower velocity out of a 16 inch barrel would inherently be quiet enough to prevent major hearing loss without any suppressor at all. (I am referring to a few shots one time for a self-defense event. Target shooting would still probably require hearing protection to avoid serious permanent hearing damage.)

        • An integrally-suppressed .458 Socom with a 600-grain subsonic (especially if it could be something like a Lehigh Maximum Expansion)? That would be so ideal I do not think I could stand waiting another minute for such a thing…

      • Most every reloading manual from the past 50 years includes 2 sections for .44 magnum. One for pistol barrels and the other using rifle/slower burning powders to take advantage of a 18 – 20 inch barrel.

        • As you can tell, I don’t load my own cartridges … so I am glad to hear that someone is publishing loading data for .44 Magnum in longish barrels.

          That being the case (published loads for .44 Magnum for 18 to 20 inch barrels), what velocities do those loads generate with your jelly-bean 180 grain or 240 grain bullets in 18 to 20 inch barrels?

      • 300 gr hard cast/flat nose .44 mag out of the newer model Ruger .44 Carbine w the rotary magazine, are impressive when they hit a deer or hog!

        You lose a little powder capacity, but we arent talking about 200 yard + targets either.

        Also got to watch the overall length of the cartridge for the carbine…..

        Shoot the same round out of my ruger blackhawk 7.5″ barrel

  5. I’d like a lightweight hunting rifle but this thing doesn’t fit the bill I don’t think. I think it’s pretty heavy but the lack of an external safety kind of kills it. I’m ok with my Glock pistols since the holster covers the trigger. I’m not going to go clomping through the woods where something could snag the trigger. This thing seems pretty impractical but is does look fun for just shooting.

    • Solutions are easy for this perceived problem. 1) get the Mech-Tech for a 1911 frame. They even chamber .460 Rowland for that. 2) use a trigger guard ‘holster’ like Raven Concealment’s. 3) don’t carry it chambered.

      And yeah, it isn’t exactly light. The biggest advantages as far as I see it are that it isn’t a firearm so it ships right to your door and it gives you two guns out of one (turns your glock or 1911 into a rifle). It’s very accurate and reliable and obviously you can mount optics and stocks and other things on it that you can’t really put on your pistol. Plus some calibers see big bumps in velocity.

      • If you go the 1911 route, be sure to get a model with a standard, non-extended thumb safety—i.e. the old thumb breaker G.I. version.
        I ran mine with a magnum research 1911 and although the thumb safety was barely long enough for comfort, the greater length contacted the curvature of the CCU housing, preventing it from engaging.

        • My quest for lightweight is at odds with a 1911 frame. My quest for a safety is at odds with a glock frame.

        • I’m not sure what your threshold is for “light weight” but glock or 1911 isn’t going to make much difference in the over all number.
          The unit is essentially a steel pipe with the action, barrel, and mounting hardwear inside. Size wise it’s very compact. The frame/receiver is made of solid heavy steel—so it’s pretty hefty to begin with. If you want the ultimate compramize in weight, capacity, and safety, I’d suggest going with a para p14 1911 with a standard safety, para block, and the 14rd extended magazine. I found the arrangement to be easily handled, but not very lively due to the overall weight of the housing.

      • 460 Rowland with para frame and extended magazine. cost of ammo is the only problem as finding the cases while hunting can be a pain.

  6. Shootingthebull410 is like Bill Nye the Science guy for the people of the Gun. I really enjoy his tests, i changed my 9mm carry ammo based on his results. Except shootingthebull410 better cuz he isnt a liberal, Al Gore global warming cool aid drinker like Mr. Nye is. Ruined my childhood when i found out he was so left leaning.

  7. My only concern with all those conversions is that you don’t get an external safety, as it’s still a Glock lower. It’s one thing on a handgun where it’s holstered when not in use, but on the rifle the trigger is exposed.

  8. 357 magnum from a carbine destroys 10 from a carbine. 125 grain jhp at 2300 fps = 1468 foot pounds of muzzle energy. 158 grain jhp at 2000 fps = 1403 footpounds of energy. Factor in the much higher ballistic coefficient of 357 bullets and it makes for a much flatter shooting cartridge that retains more energy downrange. The higher sectional density of 357 bullets means deeper penetration also. 10mm from a carbine is quite pathetic actually.

  9. I shoot hogs, big hogs, with my 10mm CCU. The only pathetic thing is what happens to the pigs! Nuff said.

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