J. Del Col wrote:
...When a cartridge detonates outside a gun's chamber, the bullet barely
moves. The cartridge case may split and the primer may go flying, but
the bullet travels only a short distance at low velocity. An
unconfined bullet can't develop the pressure necessary to hit with any
force. This has been confirmed by repeated tests...



When I was a kid and didn't know any better, we made a gun from a cap
pistol, the kind that used the circular array of 6 caps. We drilled out
the cylinder to fit a .22 caliber bullet and filed down the hammer to
hit at the edge of the shell. The barrel was clear and about 1/2"
diameter. Having done all this, we went out to the field and fired it at
a bottle. After firing 20 or 30 rounds and apparently not hitting the
bottle, we put the muzzle right into the neck of the bottle and fired.

The slug bounced around in the bottom of the intact bottle.

The cylinder must have fit the shell fairly well, because the brass came
out easily (no flaring of the end), but there was nothing past the
cylinder, so the gas from the powder burning just blew by the slug and
it got no appreciable velocity.



This sounds very much like the equally unlikely story of the redneck who
blew a fuse in his truck and replaced it with a .22 cartridge, which
then heated up and exploded, shooting him in the leg or somewhere.