Physics of Rifle Recoil

Missing figures

Recoil, commonly referred to as "kick," occurs as a result of Physical properties at work. However, it is often undesirable because it can be uncomfortable for the shooter and can reduce accuracy. The purpose of this webpage is to discuss the physics involved with rifle recoil in order to address various methods of minimizing it.

Rifle recoil is most simply explained by Newton's First and Second Laws of Motion. When a rifle is fired, a force is exerted on the bullet that projects it forward. By Newton's 1st Law, it can be inferred that and opposite force will be imposed on the rifle. From Newton's 2nd Law it can be deduced that this force can cause an acceleration (linear or angular) which results in velocity and therefore kinetic energy. Energy is also transferred into the marksman in the form of work. The total of this energy is called Recoil Energy and can be calculated.

When a gun is being held at rest, there are three forces acting on it. The weight of the gun pushes downward, and the shooter's hands exert a normal force upward on the gun as shown in Figure 2 below. The point P represents the point of contact between the stalk and the marksman's shoulder.

Image - Torque 2

[Figure 2]

When the gun is fired, the bullet is projected forward by a force, and an opposite force (F) pushes backward on the gun. Since the barrel where the force is acting is slightly above the point of contact with the shooter's shoulder, torque is created. The normal forces put on the gun by the shooter's hands momentarily become negligible.* The forces acting on the gun directly after the gun is fired can be simplified as in Figure 3. R is the perpendicular distance between the recoil force and the point P. L is the perpendicular distance between the location of the force due to gravity and the point P. The resulting linear and angular acceleration can be seen in Figure 4.

Image - Torque

[Figure 3]

Image - Torque 3

[Figure 4]

The elevation caused by the angular acceleration can decrease accuracy by altering the trajectory of the bullet, and the horizontal acceleration causes a force to be exerted on the shooter's shoulder which can be painful.

*This suggestion is not completely accurate because the shooter's grip will put a downward force on the gun when the gun is fired.