when your loading it are you letting the action slam shut by its self or are you pushing it forward yourself. I have a 7400 and noticed that if you dont pull the action back all the way and let it slam shut on its own it is very hard sometimes to close the action the last bit. Also about the earlier problem of not loading the second shell have you taken the forearm of and thourghly cleaned the main spring. Mine has jammed once on me and all that was the cause was that from carrying it in wet weather that spring got a little rusty and was using up alot of the energy there.