Can a hot weapon cycle its own action?

[Habeed]

Scenario : an AR-15 is stored in a closet in a residential house, round in the chamber and a full 30 round magazine inserted. Due to the actions of some irresponsible neighborhood kids with fireworks, the house catches fire and burns down.

When the fire reaches the AR-15, the heat is enough to cook off the round waiting in the barrel. The round leaves the barrels, and the hot gases force their way down the gas tube like always.

Will this cycle the weapon? Could the next round then cook off followed by the next and the next, emptying the magazine and sending high velocity rounds spraying from the muzzle of the stored rifle?

Is this a legitimate reason to not keep a round chambered in a weapon stored in your house?

 

[General Geoff]

If the chamber got hot enough from environmental heat to cook off a round, chances are high that the cartridges in the magazine already cooked off.

 

[darksidemxer]

i agree with General. im getting into reloading and im finding out just how delicate these primers are, i was reading how the guy left them in his garage in a steel container in the summer...came out to find they exploded and blew his cabinets off the wall lol.

 

[HorseSoldier]

+1 on the idea that the ammo in the mag would already would cook off before the receiver got hot enough to cook off rounds in the chamber.

 

[slodsm]

I too think it would cook off the magazine prior to the one in the chamber. There's a lot more metal that would take longer to heat to that temp when it's chambered.

On another note, I've had a .50 cal round cook off in an open bolt in an XM218 once, we had been firing for a WHILE and the gun was blazing hot so it takes some serious temperature to happen regardless.

 

[Habeed]

Ok, different question then.

It's a long, hot day in Afganistan and a small army of insurgents are attacking your position. Fortunately, you're good friends with the armorer and you've got yourself a little bit more ammo than the standard loadout

After firing off a couple thousand rounds, could your M16 get hot enough to start cooking off? Or would something else overheat first?

 

[desidog]

I'm an architect, not a fire warden, but i imagine that the house materials around the gun would burn out before elevating the gun-barrel to the temperature necessary to ignite a cartidge, unless it was stored with a surplus of magnesium, or something. Either way, if the house is burning down, an errant bullet in a safe direction (because you always point a gun in a safe direction!) is not a concern compared to the house.

I'd be more concerned with those fireworks-wielding kids, and their breaking-and-entry skills.

 

[desidog]

To answer your new question, Yes. The gun could cook off. With a standard ammo load through it fast enough.

Are you just spit-balling here? Cause you'd solve that problem by pissing on it.

 

[Schutzen]

More than likely and M-16 will overheat and lock up than cook off. M60's and M2's are known to cook off, but I have never seen an M-16 do so. I have seen the gas tube melt and the barrel slump when the rifle was laid down. In all cases, a lot of rounds have been expended in a relatively short time frame.

 

[General Geoff]

After firing off a couple thousand rounds, could your M16 get hot enough to start cooking off? Or would something else overheat first?

Everything else on an M16 save for the grip and shoulder stock would overheat first. And assuming the weapon still fired, YES you could get a round to cook off, however, each round would take a minute or two to heat up in the chamber to ignition temperature. As such, it's a self limiting problem, and only a few rounds would cook off if the weapon was not fired again intentionally for awhile. The chamber would cool off faster than the few cooked rounds could keep it heated.

 

[Jeremy2171]

Ok, different question then.

It's a long, hot day in Afganistan and a small army of insurgents are attacking your position. Fortunately, you're good friends with the armorer and you've got yourself a little bit more ammo than the standard loadout

After firing off a couple thousand rounds, could your M16 get hot enough to start cooking off? Or would something else overheat first?

Your extractor spring will fail before the M16 gets to hot to quit OR the gas tube will melt.

 

[rockstar.esq]

I'm wondering about the temperatures involved. While I don't doubt you can cook off a round at below red heat (in the steel) which is about 1500 degrees. I do wonder if things like the springs, linkages, and plastic components wouldn't loose temper at about 500 degrees and or get bungled up before the gun has reached the primers breaking point. Of course that implies you'd cook off the chambered round but it also might mean the moving parts necessary to cycle the weapon are inoperable before that happens. That would tend to make a strong case for leaving an AR with the mag loaded and the bolt open since it's so easy to release the bolt and get it into action - assuming it's for home defense of course. Beyond that I do agree that the rounds in the magazine will cook off before the chambered round.

 

[taliv]

not sure where some of you guys are getting your info... (sounds wack to me)

my notes from a class say that testing has shown they will start cooking off after 130 rnds and will blow up between 500-600 rnds.

 

[Broken11b]

Taliv, If thats the case, i would have blown up several M-4's by now. Rounds will cook off, but you'd have to have a few CMAGs on cyclic rate to get it that hot that fast, Ive gone through more than my full combat load as fast as i could on many occasions... melted the handguards and burned the heck outta my hands, but no explosions in the chambers yet

 

[taliv]

full or semi?

 

[jobu07]

Taliv, If thats the case, i would have blown up several M-4's by now. Rounds will cook off, but you'd have to have a few CMAGs on cyclic rate to get it that hot that fast, Ive gone through more than my full combat load as fast as i could on many occasions... melted the handguards and burned the heck outta my hands, but no explosions in the chambers yet

I went through two combat loads (420 rounds) on one occasion at cyclic rate with my M4. That is to say I dumped 14 magazines on burst as fast as I possible could. The 550 cord tiedowns for my PEQ-15, surefire, and M68 melted off but nothing cooked off... Perhaps i'm fortunate! The gun was really really hot afteward - I held it out, away, and pointed in a safe direction for some time.

 

[Broken11b]

Full auto, melted plastic, fried the 68, burned the heck outta my hands,but no cookoffs or explosions

 

[Broken11b]

and on seperate occasions, ive melted the blank adapter to the barrel, still no explosions (unless you count the armorer who wasnt too happy about damaging the barrel and fusing the BFA to the flash suppressor and barrel)... Well someone had to get rid of 600 rounds, the sgt told me to.

 

[Habeed]

Thanks for throughly answering my question. Where I'm coming from : I saw a news report where a fireman was shot when a pistol under the mattress with a chambered round cooked off.

So I wondered if the heat from a fire could cause a weapon to fire multiple rounds, or just the round in the chamber. If it were the latter, then it was incredible bad luck for the fireman to be standing in the right spot to be hit. I understand that loose ammunition cooking off doesn't have the killing velocity that a bullet fired from a gun does.

 

[taliv]

thanks to Zak for the following info:

http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA317929
Google HTML version: http://74.125.113.132/search?q=cach...mil&cd=1&hl=en&ct=clnk&gl=us&client=firefox-a

AMSTA-AR-ES-92-2
Fire to Destruction Test of 5.56mm M4A1 Carbine and M16A2 Rifle Barrels

...
ABSTRACT

This test report examines the effects of firing 5.56mm M4A1 Carbine and M16A2 Rifles at a high rate of fire until the weapon is severely overheated and destroyed due to ruptures in the barrel. This test indicated the M4A1 Carbine performs as well as or better than the M16A2 Rifle with respect to barrel ruptures from overheating

...
3.0 TEST RESULTS:
3.1 M16A2 Rifle; The M16A2 was fired continuously using 30 rounds bursts. Shown in table I are the rounds to failure, time to failure and maximum barrel temperature of the barrel. Muzzle flash increased and there was a distinct change in the sound of the weapons firing approximately 30 rounds before the barrel ruptured. There was also noticeable drooping (about 1 inch at the muzzle) of the barrel just prior to the barrel rupture. The barrel ruptured at 491 rounds with an approximately 1/4 inch hole in the top of the barrel about 8 inches in front of the chamber. The barrel was bent approximately 5 degrees and bulged in several locations along its length (see figures 4, 5, and 6). A plot of barrel temperature versus time at each thermocouple location is shown in figure 7

3.2 M4A1 Carbine. Weapon 1; The M4A1 Carbine was fired for 540 rounds. It was thought the M4A1 barrel would rupture well before this point, therefore only 540 rounds were loaded for firing. This weapons barrel was noticeably bent and bulged at the end of the test (see figure 8). A plot of barrel temperature versus time at each thermocouple location is shown in figure 9.

broken11b and jobu, I've no real reason to doubt your experience... just passing this along.

 

[rcmodel]

i was reading how the guy left them in his garage in a steel container in the summer...came out to find they exploded and blew his cabinets off the wall lol.

Never happened.
It simply cannot get hot enough in the sun or in a garage to cause a primer to explode unless the house is on fire.

M-2's and M-60 machineguns do not cook off because they both fire from an open bolt.
There is never a round in the chamber until you pull the trigger and it chambers & fires.
Only if you pulled the trigger, a round chambered, but the primer failed, then that round could cook off in a hot barrel. But the chance of that bad primer is very slim.

M-16's will suffer a barrel failure at some point in sustained fire.
They could easly become hot enough to have a round cook off before that point though.

rc

 

[Acera]

Thanks rcmodel, I was about to ask about how those open bolts weapons got the rounds in the chamber for them to cookoff. Come on guys..............

I think that some of the conditions that our military has weapons and ammo stored overseas is a lot warmer than a garage here.

 

[John Parker]

M-2's and M-60 machineguns do not cook off because they both fire from an open bolt.

No, the M2 is a closed bolt weapon. It can cook off from a hot chamber. http://en.wikipedia.org/wiki/M2_Browning_machine_gun

 

[armsmaster270]

However the M-60's are issued with 2 barrels which quick change and a pair of heavy gloves. the barrel gets too hot you change the barrel and continue firing.

 

[jobu07]

Taliv,

broken11b and jobu, I've no real reason to doubt your experience... just passing this along.

I wonder if variations in how long mag changes take had anything to do with cooling the barrel down between strings? I know I hit the mag release letting the mag fall to the fround and bent over to grab another one from the pile as I went along. My hand got a little toasty where I was grabbing the rail, even through my glove. I noticed that when I was done my support hand had migrated to the magazine as a form of support (which I hate).