To measure actual recoil, you need to know the velocity of the projectile, the mass of the projectile, the mass of the charge and the mass of the gun.

To measure pressure, you also need to know the burn rate of the propellant, the size the chamber, the plasticity of the barrel, the size the bore, etc.

It is the simple physics.

Bell essentially showed that given a momentary constriction and the plasticity of a shot shell, pressure increase is negligible. But recoil did not change. Increasing the bore size immediately after the chamber will decrease the pressure some what, but again it does not affect recoil.

Pete

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