Can ammo cook off in car in summer?

[Deleted member 66305]

I ordered some Buffalo Bore ammo for my .38 revolver. One of the warnings on the box was not to store ammunition at temperatures above 110 F because "dangerous chamber pressure may result".

Does this mean the danger exists when firing the ammo at that temperature, or are they implying ammo stored that hot could spontaneously ignite?

How hot can ammo be stored before you have to worry about rounds cooking off?

In a car with windows closed in Houston during the summer, temperatures can reach 140 F, perhaps even higher.

I asked this question before, but I think people interpreted it as regarding long-term degradation of the propellant.

 

[fletcher]

I'm going to say "no" with 99.9999% certainty. You would probably be dead, or your car on fire, before your ammo got hot enough to cook off.

 

[TAB]

Other things would go bad in your car, before your ammo went off.

now propellant degrading might( i'm not a chemist so I can't say for sure) be an issuse.

 

[RNB65]

No.
-

 

[rcmodel]

No, it cannot cook off in a hot car, unless the car is hot from being on fire.

Yes, very hot ammo can raise pressure to a dangerous level when fired. The burn rate of the powder tends to get faster at very high temperature.

Normal commercial ammo would not be a problem because it is not "pushing the envelop" to start with.

Buffalo Bore might be, and you probably should heed their warning.

rcmodel

 

[Cougfan2]

It won't cook off. However, I know that extreme temperatures can sometimes effect gunpowder and change it's characteristics. When I worked at Hodgdon Powder Co many moons ago, it was announced we were discontinueing production of HS5 (in reality this was just repackaged Olin ball powder as all Hodgdon ball powders are). We had some people that reported some unsafe pressures for loads well under the max. Finally figured out they had stored the powder in temperatures below freezing. What happened was that the ball powder had a coating that would fracture when exposed to extremely cold temperatures creating the unsafe pressures. Olin pulled the Win 296 so no more HS5.

 

[1KPerDay]

according to the reliable scientific information found in Mythbusters, it needs to be about 500 degrees to cook off.

 

[Ron James]

Only if your car is on fire.

 

[ArmedBear]

Here's something interesting, though. At the range where I'm on the board, we had a 9mm round go off in a big box of loose rounds. The rim from one cartridge hit the primer of another just perfectly when the box was dropped on the floor.

Nobody was hurt, and the round that went off was all that was damaged. It was interesting, though. I didn't think that could happen. The manager has the cracked brass to show that it did.

 

[Cougfan2]

The rim from one cartridge hit the primer of another just perfectly when the box was dropped on the floor.

Wow! That's one of those once in a million chances type of deal.

 

[ArmedBear]

Wow! That's one of those once in a million chances type of deal.

Hell, probably rarer than that.

 

[Steve C]

One of the warnings on the box was not to store ammunition at temperatures above 110 F because "dangerous chamber pressure may result".

The danger is not from the ammunition going off from the heat, the danger is just as the warning says due to increased chamber pressure (if fired).

Chemical reactions like combustion proceed at a faster rate as the temperature is increased. Cartridge pressure is regulated by burn rate thus the danger of higher pressure from "hot" ammo.

 

[ArmedBear]

The danger is not from the ammunition going off from the heat, the danger is just as the warning says due to increased chamber pressure (if fired).

Chemical reactions like combustion proceed at a faster rate as the temperature is increased. Cartridge pressure is regulated by burn rate thus the danger of higher pressure from "hot" ammo.

Better tell everyone over in the sandbox not to fire their guns in the Summer.

 

[pgeleven]

if that were the case we would have had a hundred or so incidents a day in iraq. only time the ammo cooked off was when it was left in a burning vehicle

 

[Halo]

The danger is not from the ammunition going off from the heat, the danger is just as the warning says due to increased chamber pressure (if fired).

Chemical reactions like combustion proceed at a faster rate as the temperature is increased. Cartridge pressure is regulated by burn rate thus the danger of higher pressure from "hot" ammo.

Better tell everyone over in the sandbox not to fire their guns in the Summer.

I doubt any military ammo has such a low safety margin though. The ammo in question is loaded close to the max. I've read cases of max pressure hunting loads developed for winter use being unsafe to fire in the summer for the same reason.

 

[The Lone Haranguer]

One of the warnings on the box was not to store ammunition at temperatures above 110 F because "dangerous chamber pressure may result".

I think this is meant for long term storage in sustained high temperatures. Over time, this could alter the chemical composition of the powder and cause it to increase pressure when fired. Leave in your car for an afternoon's shooting at the range? No problem.

As for a "cookoff" detonation, it only gets to about 160-170 degrees inside a car on a hot day with the windows closed. Tests have shown that it takes about 550 degrees (oven set on broil) to cause ammo to detonate.

 

[Zoogster]

No.

The warning is because more pressure is generated during hotter temperatures. A round at max pressure on a 70F degree day is above max pressure on a 95 degree day. So one designed to push the limits in a place that rarely gets above 80 and shipped to someone that shoots in a 110 degree desert could have some problems if there is not much of a pressure margin left.

Tehnicaly a gun and ammunition getting hot in your car could have higher pressures if it was ammunition designed at max pressure at room temperature.
That is one of the reasons all rounds need to be designed with a decent pressure margin of error to avoid kabooms.
The conditions under which the round is fired change from environment to environment, and even from the first round to the last.

It has nothing to do with cooking off in the car. Primers and powder ignite with no spark at a much higher temperature than any interior part of your vehicle will reach.

 

[Beagle-zebub]

Yeah, weren't those post-BP African game cartridges designed to work at low pressures in part because it meant that the heat of that continent in the summer wouldn't push the pressures into unmanagable territory?

 

[loop]

It gets to 120 in the shade during the summer around here. The most significant issues I've run into have been increased pressure due to the heat. When temps hit 120 ambient in a car they can hit 180. Max loads should be allowed to cool before firing under those conditions.

The other is cast bullets. The wax tends to melt when the cartridges are in a vehicle and temperatures are extreme. If the rounds are stored with the bullets down this is not a problem. If they are on their side or bullets facing up the wax can leak into the powder and cause fouling and loads that are squibs.

Aside from storing reloaded cast bullets with the bullets facing down another way to avoid fouling from leaking wax is to resize the complete cartridge after it is made. That tends to seal the wax into the grooves.

When I left work today it was 112. My pistol was under the seat and too hot to handle. I put it on the passenger seat and covered it with a handkerchief. It was loaded with cast bullets and two hours later I emptied the mags in an IDPA match. No issues.

I do usually load low end, though. Hot loads get hotter when the temperature gets unreasonable.

 

[Deleted member 66305]

Thanks everybody.

I think Buffalo Bore does load their ammo close to the max. If I need to defend myself with my car gun, I can't exactly ask a BG to hold on while my ammo cools off... perhaps I should take it out of the gun and keep the rounds in my pocket?

Are there any laws that prohibit carrying ammunition only in places that prohibit firearms?

 

[rcmodel]

I wouldn't worry about it.

What are the chances of you needing to use the hot gun left in your car in the parking lot, while you are inside a building at work?

It would seem you might need it instantly available while getting in the car after work though.

If it comes down to a life or death situation, I would rather take the chance on a hot round then a bunch of loose ammo in my pocket.

In that case, a high-pressure .38 Special is going to perform about like a low-end .357 Mag, and would not harm any modern .38 revolver anyway.

You can bet the 110 degree talk on the box has a built-in, Lawyer inspired, "fudge-Factor of about 50 degrees!

rcmodel

 

[ftierson]

Originally posted by loop
The other is cast bullets. The wax tends to melt when the cartridges are in a vehicle and temperatures are extreme. If the rounds are stored with the bullets down this is not a problem. If they are on their side or bullets facing up the wax can leak into the powder and cause fouling and loads that are squibs.

Certainly, depending on the bullet lube used, the warning could be related to this...

IN addition, as many have pointed out, heating ammo increases pressures when shot.

I do know that a cerrosafe chamber cast will melt if left on the front seat of your Bronco in Colorado, even in the winter. Obviously, the interior can be heated up enough to reach its melting point.

Forrest

 

[PTK]

I do know that a cerrosafe chamber cast will melt if left on the front seat of your Bronco in Colorado, even in the winter. Obviously, the interior can be heated up enough to reach its melting point.

When I got my MidwayUSA delivery recently, the cerrosafe had melted in the plastic bags it was shipped in. UPS trucks also seem to get plenty hot in the back.

 

[GEM]

Damn chocolate bullets - always melting.

If that were true - cars would exploding across TX.

 

[valtr0n]

Slightly off topic, but I've seen a round go off for no reason in the local gun store. The owner came in and opened up for the morning and noticed a big mess by the ammunition. A cartridge in a box of .45ACP had apparently discharged on it's own. The casing was present, and the primer was bulged outwards, from inside the case. Nothing had visibly stricken it. No idea what happened, but it was definitely scary.