RE: Trigger Problem
I took when he says "fired" to mean than the hammer falls when the trigger is pulled whether the gun actually discharges or not.
I also think that if he's shooting a shell that is too long for the chamber, it wouldn't chamber easily, but could still chamber when forced depending on the length and pitch of the forcing cone, when loaded because it'd be difficult to squeeze the front of the shell into the forcing cone with the shell crimped on a shot charge. But one the shell was fired the crimp would be open and there would be no shot inside to prevent it from easily squeezing into the forcing cone, thus allowing it to completely chamber with ease and allow the hammer to drop every time when the trigger is pulled.
Mike