Experimental cook-off, or science wins again

[FelixEstrella]

You've seen the movie drama, where a "bullet" thrown in the fire kills someone.

Well, I've always been skeptical. A simple understanding of physics would tell you that as the powder burns in a completely unsupported cartridge, the pressure builds up to the point where the bullet is pushed out of the case mouth. At that point, the remaining powder burns harmlessly ... well, perhaps with a little jet action on the empty case.

So, I tried it. Putting a 9mm cartridge on a sheet of plywood, I held a lit propane torch to the cartridge until it "cooked off". Sure enough, there was a loud bang, the case jetted harmlessly across the garage floor, but the bullet remained, almost unmoved, sitting on the plywood.

Science wins again.

[Jeffro]

I've had .22s go off in the vacuum cleaner - it is somewhat disconcerting to hear a bang while cleaning house. Usually, the bullet remained seated with a small flap blown out of the side of the case, also blowing out part of the crimp.

[308Mike]

Yet a cook-off in a barrel (or chamber) is another matter entirely.

There are various ways a round can cook off, it can go primer-first, which would probably be the most dangerous to bystanders since the powder would start burning normally until the case pressure exceeded the friction (or crimp) holding the bullet to the casing. A powder ignition without the primer going off is probably the safest type, and hopefully the case is heated unevenly causing a unsymmetrical expansion of the case with subsequent relief of the expanding burning gases of the powder.

This *could* make an interesting science project for some deserving high-school student to present to his GWF peers and teachers (and administration). Educate them through science.

[FelixEstrella]

This experiment implies that storing ammo in steel boxes provides safety to firefighters who may be trying to extinguish a fire in your house.

[308Mike]

I wouldn't assume as much. Try throwing some loose rounds into an ammo can (with extra cardboard as required to simulate your situation) and set it into a firepit and see how things do with various cook-off temps, etc......

[Mud_Dog]

This experiment implies that storing ammo in steel boxes provides safety to firefighters who may be trying to extinguish a fire in your house.

Unless they are linked and in their original box. When the cartridges are all together they provide the neccesary pressure needed to send those rounds flying.

Trust me, I have the pictures to prove it. Or rather, I will if I can remember to take the pictures out of my toolbox later this week and bring them home to scan 'em.

7.62 NATO linked does not like burning trucks...

[DwightG]

Gen Julian Hatcher wrote about this topic in Hatcher's Notebook. Any who haven't read it should do so.

[workinwifdakids]

Good experiment, but Mythbusters got to it first.

[FelixEstrella]

Good experiment, but Mythbusters got to it first.

(a) I don't have a TV.
(b) It's fun teaching kids the difference between Hollywood and Physics
(c) As a friend of mine so succinctly said it, "I have an unbounded enthusiasm for all things that go boom".

[Fivetoes]

Seekher unwillingly did this in real life a couple years ago.