Animation for weapon problem (lock/slider, reload)

Hello, I am new in Unity 3D but I have made some good fps game just by myself scripting js but the problem is i don't know how to use animation tool... I have created and saved actual animation for the lock/slider of the weapon (the place where shells come from when you shoot) so it comes back, and forward. When "Animator" is ON than the animation just loops and when I add "Animation" to the weapon it doesn't change anything. I have added like Stop and Play lines (because it should only play when I press mouse button) to the weapon script but it didn't help as well so please help me because it probably is a veeeery simple thing that I don't know. Thanks, greetings from Poland I don't have Pro version.