[gatex]

"I put it in a bench vise...."

If the vise was clamped on the cartridge case where the bullet was and held the bullet in while the heat built up and caused the powder to burn, the resultant gases could build up presure until somrthinge broke --- but that is not the same result as when the cartridge is heated without the bullet being restrained.

[blackdog]

I searched all over the house looking for a bullet hole in each ceiling, thinking it narrowly missed my chin. I was surprised when no hole was to be found. When my dad was done beating my arss, he explained the physics to me. Both the shell and full jacketed round were lying on the basement floor in front of the workbench. Even being in a vise is not surrounding pressure. He made sure that my strict adherence to "no guns without adult supervision" also included ammo at that point.