Follow up question re recoil and "porting."
How much does "porting" reduce recoil? And, are their any "side effects" to porting other than too bright a flash for night shooting? Can any pistol be "ported?" Am I correct to assume that the more the recoil can be reduced the easier it is to hit a target, all else being equal?
Thanks to all who respond.
Recoil, muzzle jump and porting
I think you have to define your terms carefully in this discussion of recoil, porting and muzzle jump (or rise). I would tend to define recoil as the force of the gun pushing straight back along the axis of the barrel, and muzzle jump as the upward force at a right angle to the barrel. I believe that muzzle jump is primarily caused by the torque of the recoil force around the grip of the gun, where the hand is holding the gun. Muzzle jump results from the fact that the grip is lower than the barrel axis, and the recoil force causes a rotation we call muzzle jump.
Porting allows some of the expanding propellant gases to exit the gun in an upward direction perpendicular to the barrel axis, producing a downward force on the barrel due to the thrust of the gases, much as the exhaust from a rocket motor produces thrust in the opposite direction. So porting tends to cancel out muzzle rise.
But I don't think porting does much for recoil, the force straight back along the axis of the barrel. That is because the force of the porting is perpendicular to the barrel, and therefore does not have a component or vector in the axial direction.
There might be a second order recoil reduction because porting lowers muzzle velocity and hence recoil. This might be on the order of 10% or so. But you can use weaker ammunition and get the same effect.
So I conclude that porting reduces muzzle rise but not recoil.