Don't store any rounds in the chamber of a weapon, or a revolver cylinder, that's for sure. It cooks off, you've fired a round, then ballistics takes over. The loose stuff will just burst open, it's not confined in a chamber. Buddy of mine was on a volunteer fire crew some years back, another crew member got a bullet in the leg from a loaded weapon on a shelf. They backed off and let the rest of the house burn down. Can't say I blame them.