Free Recoil
The calculated recoil energy of the rifle by itself, before the shooter's hold and body reduce the recoil that is actually felt.
Free recoil is the theoretical recoil energy of the firearm considered on its own, with no shooter behind it. It is computed from the rifle’s weight against the mass and velocity of the bullet and powder gases, and it is usually expressed in foot-pounds. Because it ignores the shooter, free recoil is a clean way to compare cartridges and rifles on equal terms.
Felt recoil is always less than the free-recoil figure, since the shooter’s grip, stance, and body absorb part of the impulse. Hardware changes the equation too: a muzzle brake redirects gas to cut the rearward push, and a heavier rifle lowers both the energy and the muzzle rise that disturbs the sight picture between shots.