Recoil versus energy

The energy delivered to the target of a firearm is equal to one-half of the mass of the bullet times its impact velocity squared. The energy delivered to the shooter is equal to one-half of the mass of the combined shooter and firearm, for typical firearms, times the squared velocity of the shooter and gun.

Perception of recoil

For small arms, the way in which the shooter perceives the recoil, or kick, can have a significant impact on the shooter's experience and performance. For example, a gun that "kicks like a mule" is going to be approached with trepidation, and the shooter will anticpate the recoil and flinch in anticipation as the shot is released. This leads to the shooter jerking the trigger, rather than pulling is smoothly, and the jerking motion is almost certain to disturb the alignment of the gun and result in a miss.

Dealing with recoil in mounted guns

A recoil system absorbs momentum, for example, by the barrel moving backwards. Cannons and such weapons without a recoil system roll several meters backwards when fired.

Misconceptions about recoil

Hollywood depictions of firearm victims being thrown through plate-glass windows are inaccurate, for if this were the case, the shooter would also be thrown backwards with equal force. Gunshot victims frequently do collapse when shot, which is usually due to the effect of the energy of the bullet acting on their central nervous systems, and is not the result of the momentum of the bullet pushing them over. Of course this does not apply if the victim is hit by heavy weapons fire, such as aircraft cannon, where the momentum effects can be significant. The recoil from such a weapon is equally enormous, and requires it to be mounted on a weapons platform.