@TaoSan; not per se. The same amount of momentum must be transferred to the gun and its operator, because momentum is the product of force and time, the gun feels the same force as the lock, by Newton’s third law, and the force clearly acts on both for the same amount of time. But while the force on the lock acts only over a distance of some six inches or so, when the operator tries to slow down the recoil he can do so over the entire length of his arms; and because the gun is much more massive than the bolt, it will cover this distance considerably slower, as well. So the time over which the force of his arms can act is much greater, and therefore the force he must use is proportionately smaller.
That deals with the question of whether the shooter would have enough strength to handle the gun. As for what happens to his body afterwards: ultimately, as momentum is conserved for a system, he and the gun must collectively have the same momentum as the lock, but momentum is also the product of mass and velocity; as they are much more massive than the lock, they will move backwards much more slowly. Not knowing the specific values in the system, and allowing that considerably more force is needed than that described, given that some momentum is transferred to the door by friction, I cannot say whether it would actually be possible; but its is not a simple open-and-shut case.
However, the whole thing with people flying backwards after getting shot is clearly impossible, because the difference in mass between a bullet and a gun is insignificant compared to the masses of two people, and so each person’s momentum, and therefore velocity if they are of the same weight, should be approximately the same. Of course, the shooter may have braced themselves while shooting, thus transferring momentum to the earth; but if they are simply standing, running or falling as they usually are in movies, they would have to flay backwards just as far as their victims do; and since they don’t, it is clear that the victims ought not to either.