Physics of the Firearm

Of the above listed firearms the bolt action rifle is the most widely used for hunting wild game so that is the type of rifle I will be explaining the physics of.

Bolt Action Rifle:

Looking at the image below you can see a spring inside of the bolt. When the firearm is charged, the spring is set in a compressed position. Once the trigger is squeezed it releases the spring and the spring drives the firing pin forward striking the primer on the cartridge.

In modern physics the spring can be explained using Hooke’s Law while treating the length until the spring is compressed as the value for “x” or displacement. The equation is: F = kx. Using F = kx, the spring constant, k, can be determined once all of the forces are determined and the displacement is known by rearranging the equation like this: k = F/xand then solving for k. The restoring force of the spring is then F = -kx. Another useful perspective into the spring of a firearm is possibly looking at the energy of the spring. As the spring is compressed the force varies linearly and as seen from Hooke’s Law force is proportional to displacement. Using this definition, the total work to draw the spring back can be calculated using the equation W = Fx, where W is work, F is force, and x is the displacement of the spring from rest. The spring’s potential energy can be determined with the equation: U = 1/2 kx²_.The spring’s kinetic energy can be explained using the conservation of energy law and a known value for potential energy. The trigger is the releasing mechanism for all of the potential energy in the spring to turn into kinetic energy while the spring works back to equilibrium.

Most firearms use a spring or similar system so the interchangeability of these equations between multiple firearms is very possible assuming the mechanisms are known and are relevant to the equations. There are multiple other physics related data concerning the firearm, especially when the bullet is fired, however I chose only to use the spring as an example.