It's very possible that it happened. I've seen a9mm go off by dropping the box of ammo. Any kind of jolt can set stuff off, maybe it's a mistake in how it's made but it does happen. glad to hear you're ok.
-Jake

Some powders are more heat sensative than others, along with the fact that some powders can change property when vibrated enough, that's why you're not suppose to put loaded ammo. through a tumbler.

Just because Mythbusters can't replicate something certainly doesn't convince me that it can't happen. They couldn't even get a robbin hood with arrows!

Just like the guy that I posted about earlier that had handgun ammo. on his dash, isn't it strange that not all the ammo. went off, but instead only 2 rounds of the box of 50. He also posted pictures of that incident. SO, no doubt it CAN happen.

When a smokeless round goes off outside of a gun chamber, the pressure builds up to the point that the case is separated from the bullet. Since it has less massthan the bullet, the casebecomes the projectile, if any....

well i doubt it was the heat. I left at least one or two in my pants they got washed and dryed no fire. Now i guest the washer could have gotten the powder wet but it looked sealed to me.

I don't see how it could happen, either. It's not enough to strike a .22 on the rim, there has to be something to strike against, i.e. it's a hammer-anvil effect. The firing pin hits one side of the rim while the other side is supported against the edge of the chamber. The firing pin crushes the priming compound between the brass lips of the primer.

The batteries? There's an electrically primed muzzleloader on the market, but that's black powder with an ignition system designed to set it all off.

I always change the batteries in my household smoke detectors during the time changes. Last year while doing this task I had the fresh batteries in my front pants pocket. When changing I would place the old battery in my shirt pocket and and replace it with a fresh one from my pants.

Later that morning I felt my shirt pocket was getting warm and discovered that one of the nine volt batteries had shorted out against another. I removed them from my pocket and just for the heck of it I snapped two of the batteries together. Within only a few minutes they became too hot to handle.

I got to thinking that could be a fire hazard if they got together in a trash can. I now put electrical tape across the electrodes before discarding.

This has nothing to do with shooting but just something I wanted to pass along to everyone.

Just because we don't understand the conditions under which it happens does not mean that it is impossible. There are enough stories around about such occurrences that we know it DOES happen.

rob94: What are you thinkin' man! This is law suite city, buddy! If a feeble-minded little old lady who spilled her hot coffee in her lap can get millions from McDonalds, what about you! Talk about pain and suffering, you'll probably suffer the psychological scars of this experience forever!

Just joking. I'm glad no harm was caused. Odd things do sometimes happen. Maybe you dinged the edge of the cartridge enough to set it off (it is a rim-fire type cartridge). Maybe the heat? If it hasn't already been said, the pressures created by gunpowder depend upon confinement. Set off a coffee saucer of 50 grains of nitro smokeless powder with a match and then compare that to a .30-06 shot from a gun. Fortunately for you, not much confinement of the combusting powder out of the chamber and barrel of a gun.

If 110-120 degree heat could cause a shell to go off, then there would definitely be problems for our soldiers in Iraq and Afghanistan, or in non air conditioned houses in Arizona and Nevada......