There is a number of reasons why the sliding breech is the best, one is that when you lengthen the transfer port this will lower the power. Also there is very little wear to the barrel seal as it pushes onto the barrel and not rubbed over it. The BSA rotating breech wears the O ring around it so you loose compression and the O ring that seals the barrel , a number of other designs also suffer from leaks. the slot in the bottom of the action for the pellet to fall though was a copy off the Venom Mach 2 rifle.