# Gun recoil

How the gun recoil force is calculated.

## Answers and Replies

Gun recoil force for a time t can be calculated by knowing the change in momentum that takes place before and after the shot takes place.Generally in problems you will be given the velocity with which the bullet leaves the gun ....So you can calculate the "backwards reaction momentum" by simple application of "conservation of momentum.

Suppose:

A gun of mass M shoots a bullet of mass m and this bullety leaves the gun with velocity $V_o$ and as a result the gun goes backwards with velocity $V$

Therefore ina short time t :

$Ft=MV-mV_o$

Andrew Mason
Homework Helper
Dr.Brain said:
Gun recoil force for a time t can be calculated by knowing the change in momentum that takes place before and after the shot takes place.Generally in problems you will be given the velocity with which the bullet leaves the gun ....So you can calculate the "backwards reaction momentum" by simple application of "conservation of momentum.

Suppose:

A gun of mass M shoots a bullet of mass m and this bullety leaves the gun with velocity $V_o$ and as a result the gun goes backwards with velocity $V$

Therefore ina short time t :

$Ft=MV- mV_o$
I think you meant:
$Ft = -MV = mV_o$

AM

Danger
Gold Member
Dr.Brain said:
So you can calculate the "backwards reaction momentum" by simple application of "conservation of momentum.
Note also that if you're looking for an 'actual' as opposed to 'theoretical' solution, reaction torque from the rifling must be accounted for. It's insignificant in a rifle, and non-existent in a shotgun, but is very noticeable when you get into magnum-calibre handguns.

Andrew Mason said:
I think you meant:
$Ft = -MV = mV_o$

AM

thanx.. actually the change in momentum for the gun is to be taken and not the change in momentum for the gun-bullet system