the reaction to the slugs released from the bullet has to be strong enough to clear the chamber and eject the spent cartridge. [low powered loads jam] If not the gun jams on the next round, pushing it sidewways towards the breech but not actually going to battery. Badly designed bullets may not feed correctly which is why most automatic ammunition is pointed round nose. For instance, square .44 bullets cannot autofeed, thus sliding them into a revolver is the way to go. Also snake shot is best fired from a revolver because the force of the bullet is not required to make the action work. There is a reason machine gun bullets are pointed - so they feed well.
Jim <img src="/forums/images/graemlins/cool.gif" alt="" />