Originally Posted by
country1
You do loose velocity from a revolver cylinder gap. Gases from the burning powder are expelled through the cylinder gap. A ported barrel in a revolver may increase the velocity of a bullet, but there is definite velocity loss from the cylinder gap. Find someone with a T/C Encore in .357 Mag. Fire a .38 Special round from that and compare it with the same ammo type fired from a revolver with the same barrel length.
No one is arguing that energy/gases are lost through the BC gap, it's a known fact.
It's also a known fact that semiauto pistols, of ANY design, blowback, short recoil, gas-operated, etc, ALSO lose energy via mechanical resistance of moving the slide/bolt, as well as venting gases through the breech.
My point is that the venting of gases does NOT explain why a 9mm pistol is more powerful than a .38spcl revolver. THE PRESSURE DIFFERENCE DOES!!!
If you really want to split hairs, revolvers have an advantage because a 4" revolver will have a longer barrel than a 4" pistol. Revolvers barrels are measured from the rear end of the barrel, essentially THE FRONT OF THE CHAMBER, while pistols are measured from the front of the breechface, essentially THE REAR OF THE CHAMBER. The nose of a 9mm will actually have LESS barrel in front of it in a 4" pistol than the nose of a .38spcl will have in a 4" revolver, so essentially, the .38spcl would have potential to actually have MORE energy due to it's longer barrel, but it DOESN'T.