Recoil
The rearward push you feel when the rifle fires, the momentum of the bullet returned. Heavier rifles and muzzle brakes both reduce felt recoil.
Recoil is conservation of momentum applied to a bullet leaving a barrel. The bullet goes forward; an equivalent impulse pushes the rifle backward. Felt recoil (how hard the gun hits your shoulder) is a function of bullet weight, velocity, rifle weight, and gas energy.
Magnums punish; .22 LR is delightful. Most of long-range training is about managing the rifle’s behavior under recoil so you can spot your own impacts without losing the target.