After running a fast string of 50ish practice rounds through my trusty Glock, I finished practice and set the gun back up into its usual carry condition. As I re-holstered it in the appendix position with a round in chamber, a thought popped into my head. I’d fired the fifty rounds fast…what if the pistol was so hot that the round in the camber cooked off? I don’t know what the actual risk of this is . . .

But I’ll be honest — it unnerved me a bit. I unloaded the chambered round and didn’t replace it until the gun had cooled off. The round I’d unloaded was warm to touch, but not so hot I couldn’t hold it. So here’s the question: is it even possible to cook off a round in a hot pistol? How many rounds would it take to get a pistol toasty enough to do that?

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54 Responses to Question of the Day: Can You Cook Off a Round in a Hot Chamber?

  1. Well the temperature of combustion of paper is 454F. Assuming that powder is similar I can’t imagine the chamber being that hot and not melting other bits of the gun.

  2. I would love to see how you could test that little question in a safe manner!

    I bet if you ask some of our current or former military people that served in hot climates that lived through some fire fights could tell you.

  3. Somebody send me a Glock and a couple jillion rounds to test this theory out! Oh and somebody to load the magazines while I do all the trigger pulling…

  4. Theoretically, yes. Practically, no.

    I have been in the military since 1986. I have seen belt-fed weapons run really hard. Barrel-glowing in the night hard. I have never witnessed a round cook off. I have belted and fired 1000 rounds of 7.62mm from an M60 and not cooked off a round.

    In a pistol, you would need to fire so many bullets that the logistics of reloading the gun would be staggering. But let’s argue that you had an infinite number of drum magazines and somehow reloaded to the point that the chamber was so hot it would cook off a round. You would not be able to hold or holster the pistol. Remember that machine gun chambers are several layers of metal away from service members hands. Yet the gun tells you it does not want to keep going. There is an asbestos glove just to handle barrel changes.

    If you are wearing asbestos gloves and firing an all metal gun with access to unlimited drum magazines….. then yes. In reality, it is on the level of a toilet snake.

    • Belt fed weapons are usually (always?) open bolt designs. One reason for that is so they don’t cook off rounds.

      I do, however, agree with your conclusion. Cooking off a round in a handgun will not happen because the gun would be too hot to handle with bare hands.

      Does anyone know of a closed bolt, belt fed machine gun?

      • The famous Vickers machine gun of WWI was belt fed, closed bolt, and highly successful. It did, however, require a water cooling system to avoid barrel overheating.

        • M2s also have a very slow cyclic rate and aren’t fired for extended periods of time. No good machine gunner pours out long, barrel-burning streams of fire if he knows what he’s doing. Short bursts are best.

      • The M2 is a closed bolt design. Never experienced a cook off and I have had the opportunity to “get rid” of bullets due to fiscal year ending.

    • Browning .50s and .30s can definitely do cook-offs.

      More modern guns derived from the German MG 42 (ie. M-60, M-240, G-3, etc.) don’t, because of the open-bolt design.

    • Back in early 1970 while at Ft Ord, the NCO’s set up two M60’s with 5000 rounds each for demonstration. Before the ammo was exhausted both were cooking off rounds with the operators just holding the handles not squeezing the triggers, so yes in my personal experience they can! It was also at night, and as the barrels heated up (and I’m talking glowing red) the rounds down range started dropping lower and lower even though they were still aiming in the original spot.

        • They were, hence the tracers rounds were looking like rainbows as they arced to the targets. If I remember correctly, they were using up old barrels for the demo!

  5. Mythbusters had an episode with a round in revolver cooked in the oven and it went off after the oven was hot enough. So it’s possible but in real world scenario you would have to fire tons of rounds to keep the Glock hot and at the same time keep the round long enough in the chamber to cook and go off on its own.

    Mythbusters had another experiment which they threw lots of different types of ammo into a campfire and they all exploded but since it’s not chambered the casings caused more damage than the bullets, just a thought.

  6. I agree with Sid but I am not ex-military but rather an engineer who has worked on military weapons systems on helicopters.

    I have also been to and participated in various gun competitions where AR’s and some race pistols are literally smoking at the end of a run but have never seen an accident due to burned off round.

    At the range I have seen more FTF, FTC or FTB due to built up carbon that needed to be picked off due to dirty ammo then any such incident with a hot pistol.

  7. Don’t worry with a semi auto. Like the post above I’ve shot belt feed weapons (M249 and M240) till the barrels started to glow at night and never had a round cook off. We swapped out the barrel when it started to glow but kept shooting (had two extra barrels per gun). If the barrel in your glock got as hot things would be melting and skin would be frying but the round wouldn’t cook off.

  8. Isn’t the possibility of that the reason that belt fed MGs lock open after each trigger pull? Otherwise the risk is that the weapon “goes cyclic”. I think the likelihood of this happening with a gun cool enough to wear is infinitesimally small.

    • Yes, they’re open bolt, so a round is not in the chamber unless it’s actually being fire. Unlike a closed bolt weapon where the bolt chambers a round and the trigger hits the firing pin, an open bolt weapons trigger releases the bolt carrier from the rear. The act of the bolt closing also causes the firing pin to strike the primer.

  9. I’m sure somebody will be selling a CPD (Cook-off Prevention Device) very soon for $19.99, and there will be plenty of forum posts and even gun bloggers naming it a “must have” for the *serious* tactical shooter.

  10. I do testing in this field, and I’ve pulled rounds out of guns that were too hot to touch and have never had a cookoff in either a pistol or rifle.

    On test I had a .45 semi auto too hot to hold and did not have a cookoff.

    A note to those comparing glowing hot belt feds such as an M240, M60, M249, etc… those weapons are designed with an open bolt for a reason, and unless a round is actually chambered it will not cookoff. I believe you’d see very different results if those weapons were closed bolts with a round left in the bolt.

    Eric, feel free to email me and we can chat a little more candidly about my experiences and back ground.

  11. Search on the Internet and you’ll come up with:
    Black Powder ignites at 801degrees F
    Smokeless Powder varies, but an accepted Minimum is 800 degrees F

    I think if your pistol got 800 degrees F it would be so hot you would have no doubt that you don’t want to put any live rounds in it, possibly much less be able to hold onto it with bare hand.

    • In my first Reply to matt I screwed-up the HTML Link and have asked it to be deleted. The MSDS he got from Accurate Arms are, I am certain, better information than I found, which was a general “Ask” type Site.
      So, better to go with those lower numbers for Safety’s Sake.
      Thanks! DerryM

    • Got it off a general info site, but the MSDS you found is, I am sure, better information, so doesn’t matter where I got the apparently inaccurate info.
      That’s what I get for doing a quick search on the Internet…I was having trouble believing no one else could quote ignition temps and was about 3 minutes away from having to leave for an appointment, so I rushed it all….Bad idea!

  12. I’ve put PLENTY of rounds through full-auto machine guns in the desert @ 120+ degrees, and have never in my life seen a cook off. And that includes cherry-red barrels. You’re GTG.

  13. I seem to recall a YouTube video of Todd Jarrett firing off 1000 rounds of .45 as fast as he could, with people loading mags for him. Something like 10 minutes of nearly constant fire. No cook-offs, but the gun did burn his hand.

    • The point is that the gun did not get hot enough. I’d pay money to see someone do the same thing, then leave a round in the (very hot) gun. Hell, I’ll volunteer to hold said gun if TTAG will sponsor the ammo.

  14. I’ve had a cook-off rapid firing an M249 SAW on a 110-115 degree day. Well, it was either that or a malfunction – which has been known to happen with a belt fed full auto machine gun which fires from an open bolt.

    I seriously doubt it could happen with a Glock, which I’ve rapid fired for about 100 rounds (ran out of magazines), but not nearly as fast as the video. However, I would take any chances with a loaded firearm pointed directly at “Mr. Bojangles.”

    • How could you get a cook off from an open bolt machinegun? Sounds a lot more like a malfunction, since a lot more than just the round getting too hot would have to happen for it to go off.

      • I have occasionally (several times now in my time in the military) seen rounds cook off even in open-bolt machine guns like the M60 and M240. The cause is invariably a misfired round which is left too long in the chamber. Even though it fires from the open-bolt position, if a round fails to fire when chambered, it can still cook off if not immediately (within 10 seconds) ejected. Failures to extract or eject can further complicate matters.

        The M2HB and predecessors, on the other hand, which are closed-bolt designs, cook off commonly if a round is left in the chamber too long.

        Both the M2HB and M240 are considered to have reached potential cook-off temperatures when 200 rounds have been fired in a 2 minute period.

  15. As pointed out, machine guns fire from an open bolt or they would indeed cook off.

    The question is if one fired a pistol 300 rounds, then chambered a round without firing and left it in the chamber long enough for the heat to transfer to the cartridge. It is not the absolute temperature that is the issue, it is the absolute temperature plus the dwell time of the cartridge.

    It would be an interesting experiment. I don’t think I have enough mags to do it, but maybe I can borrow some.

  16. I seem to remember a torture test of a Glock when they first came on the scene. The shooter (I believe it was John Taffin) had a stack of loaded magazines and 2 guys to reload them as he emptied them. The point was to shoot until the gun had a malfunction of any kind. If I remember correctly the gun got too hot to hold, so he continued to shoot it with gloves. I would have remembered if they had a round cook off, because it was that article that motivated me to buy my Glock 20 some odd years ago, and a cook off round would have stopped me from making the purchase.

  17. Ex-Army, with no cook-off experience in the 1911… but a few cook-off experiences from neighbors using M16 A1 & A2… plus a “gas ring” misfire issue with an M16 A1 (gas ring alignment causing full auto uncontrolled fire). I just don’t think you’d ever have an issue with the pistol, unless you were standing next to a forest fire. The M16’s ability to overheat under full auto was famous, so it shouldn’t be a surprise.

  18. to put some historical perspective on the discussion the VZ 58 in its proto-type stage did have some issues cooking off rounds after 180-200 rounds were fired in full auto but that was fixed before mass production, so it is definitely possible for rounds to cook off in a closed bolt system but as others have stated for a pistol to do that would be extremely impractical cause you would be feeling the heat as well.

  19. In the military I’ve seen some major malfunctions in guns but I don’t recall ecer seeing a round cook off. As a civilian shooter I’ve never seen anybody cook off a round. Does this make it impossible? I’m going to go with damned unlikely to near impossible. A person would have to create the “perfect storm” scenario for this to happen.

    On a funny note and even sort of related to a cook off I once saw a youtube video of an Iraqi insurgent rapid firing a mortar. Every time he fired he shouted “allah akhbar” right up to the round that exploded in the tube. Was that a cook off? I don’t know but I lol’d at the reward Allah sent that guy for being a holy warrior.

  20. Possible, yes. If you shove a round into a metal gun and hit the chamber with a torch, eventually it’ll fire, after exposure to a thousand-plus degrees for at least several minutes (best guess).

    Possible in normal, or even abusive use of a firearm? No. I’ve done more than a few thousand-plus round torture tests (read: fun) on various full metal and polymer pistols, and I’ve never had one cook off, even when the thing was painfully hot to hold on to.

    Hence, relatively simple go/no-go: Is the firearm too hot to physically hold? If not, you’re good.

  21. A low-profile friend (with a career you could write novels about) witnessed cookoffs after his unit’s CAR-15s were sometimes employed as LMGs to deliver sustained automatic fire. After firing full-auto for 500+ rounds as fast as they could swap magazines, the CARs (predecessors to the M4) were too hot to touch without gloves, and the unit started experiencing unintended discharges.

    Operator error is the typical cause, but several of discharges occurred under circumstances where there was no possibility of operator error. Slung weapons and weapons placed on the ground to cool off were discharging themselves, and the just-fired weapons were found to have their safeties still engaged.

    Normal mission weapon carry, with a round chambered and the safety engaged, could not prevent unintended discharges after really excessive sustained firing: the barrel and bolt were hot enough to ignite a round after a few minutes in the chamber.

    His unit adapted their training and doctrine to require that overheated weapons be carried with the bolt locked open until they’d cooled down. The noise of slapping your bolt release prior to combat might alert hostiles to your presence, but nowhere near as badly as an unintended discharge would.

  22. I doubt it… I can only comment on my own experience though. I’ve gone to the range god knows how many times and fired all 9 ten round magazines in rapid succession. Just because it’s fun to do that sometimes, and never had a problem. Never say never though. If your gun cooks off a round after shooting 50 rounds you should buy a lottery ticket.

  23. The spontaneous combustion temperature of guncotton is 430 F, modern single and double based powders are in the same range, but will vary slightly due to the actual chemistry.

    In other words, it’s not going to cook off in a pistol.

  24. In order to have a chance to cook-off, a round would need to be left in the chamber. That 1,000 round test of the Glock 19 didn’t include leaving a round in the chamber long enough for it to become super-heated. Test is thus inconclusive concerning a cook-off.

  25. Because of the inherent self-cooling aspect of the autoloading pistol action, it is very unlikely that the chamber would reach a temperature high enough to transfer heat through the ammunition casing and heat the primer to the approximately 380 degrees required to detonate. Given that semiautomatic rifles under sustained fire do not reach the required temperature to do so, one would deduce that a handgun is far from capable of heating a round to the point of autocombustion. Just my two cents.

  26. I used to demonstrate rounds cooking off in a belt fed machinegun. The gun was a Browning 1919A4 which fires from a closed bolt. Using linked ammunition so the quantity could be controlled more readily(cloth belts only hold 250rds normally and take a while to change) I would fire a burst of 300rds and then leave the gun sitting. After about 5 seconds the next round would fire due to cook off, about 8 seconds later the second would go….each round took a little longer to fire due to cooling of the barrel. The most we ever got to fire with no trigger work was 11 rds and the last took 24 seconds to fire after the previous. Cook offs are possible in other guns and I have seen rounds ejected from a hot chamber in an AK (full auto) fire while in the air. It is something to be aware of can care should be taken. I’m not aware of any pistol caliber firearm that would heat up enough to cook off a round. I know firing 9mm and .45 cal submachineguns I have never seen the barrel hot enough to boil water much less to ignite a cartridge.

    Timmy

  27. Confirming just about everything said above, this video shows what looks for all the world like a true cook off from a G17. Of course, this was in no way under standard conditions: gloves on, FA conversion, and an endless supply of extended magazines.

    So, possible? If you really really want to.
    Likely? Like Sid said, toilet snake.

    https://youtu.be/ub4OswUhLwo?t=276 (at 4:39)

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