How much of the recoil is due to the high speed gases exiting the gun. I ask because isn't that how muzzle breaks work? Don't they direct the high speed gases backwards, so that instead of a certain number of grains (same weight, remember) of gas flying out the front at 5000 ft/sec, it goes to the side, and thus produces less recoil?
I don't have the numbers but the gasses have mass too. This is one reason why blackpowder guns have more recoil for the same muzzle velocity with the same weight bullet because you need a couple of times the weight in propellant to produce the same speed and that means more mass to cause the reactionary force. I also read somewhere that the expanding gasses will push against the muzzle, when there is no brake, and add to the recoil from the reactiontary force (terminology?).