If one were to increase the size of his gun and the bullet in PROPORTION...for example, 5 times the mass of the gun and 5 times the mass of the bullet...would the recoil experienced by the shooter be the same as the recoil experienced by the same shooter where the masses were not increased? For example: A normal sized gun of 20 kg, and a bullet of 2 kg (these were made up by myself and are not actual measurements). Increase the masses by 5, giving us a gun of 100 kg and a bullet of 10 kg. Would the recoil experienced by the same person be exactly the same in both cases? Here is how I initially reasoned it: F = ma. Assuming that an acceleration of 100 m/s² is required for the bullet of 2 kg, the force that the bullet feels is 200 N (F = (2kg)(100m/s²)). The equal and opposite force on the gun would be - 200 N (because every action has an equal and opposite reaction). Therefore, the acceleration felt by the gun would be -10 m/s² (-200 N = (20kg)(acceleration)). Increasing the masses proportionally, we now have a gun of 100 kg and a bullet of 10 kg. If the masses increase, the force required in order to produce the same acceleration for the bullet would also have to increase. Therefore, 5F = 5ma...F = 1000 N. The acceleration of the bullet will still be 100 m/s². The force that the gun experiences will be equal and opposite: -1000 N. Therefore, the acceleration the gun experiences will be -10 m/s² (-1000N = 100kg)(acceleration)). In both the 20 kg and the 100 kg gun, the recoil accelerations are -10 m/s². From these calculations I deduced that the recoil experienced by the same shooter must be the same. However, I would like to verify if this is correct.