Most bullet cases are made out of brass. I'm no rocket scientist, but brass cases would make a horrible rocket engine material.
The only reason cases don't catastrophically fail when you fire a gun is because of the bolt/chamber providing support.
Brass IS pretty good about stretching quite a bit before a catastrophic failure. This property is what allows case fire-forming (http://en.wikipedia.org/wiki/Fire_forming). It's also a pretty awesome safety feature.
Cases are so bad by themselves about containing the force of expanding gas, that ammunition fires aren't nearly as dangerous as you might expect them to be. (https://www.youtube.com/watch?v=3SlOXowwC4c) It's a long video, but if I recall correctly, it demonstrates that a rifle cartridge fired without a chamber doesn't have the energy to penetrate cardboard at like an 11 inch range.
I had a box of cartridges in a fire - they didn't go more than a few inches. The cartridge fragmented, like a firecracker with no net momentum to the bullet in any particular direction.
The only reason cases don't catastrophically fail when you fire a gun is because of the bolt/chamber providing support.
Brass IS pretty good about stretching quite a bit before a catastrophic failure. This property is what allows case fire-forming (http://en.wikipedia.org/wiki/Fire_forming). It's also a pretty awesome safety feature.
Cases are so bad by themselves about containing the force of expanding gas, that ammunition fires aren't nearly as dangerous as you might expect them to be. (https://www.youtube.com/watch?v=3SlOXowwC4c) It's a long video, but if I recall correctly, it demonstrates that a rifle cartridge fired without a chamber doesn't have the energy to penetrate cardboard at like an 11 inch range.