Can two bullets occupy the same barrel...?

[abraham743]

Once the breech opened all pressure behind first bullet would be gone. If a second bullet could be chambered before first left barrel, the first bullet moving away from second would initially create a vacuum slowing travel of first bullet. When second bullet is fired is when high barrel pressures would be realized. This may all be BS as it came from my head lol

 

[Tebow]

I remember watching CSI: New York one time, there was a bank robbery and the robber used a gun that fired two bullets into the same exact spot on a guy.