I have a friend Rem 7400 apart for cleaning. It some times would not fire the first round. I put it back together and now it fires first time will lock open on the last round but will not fire after being shot once. 1. it will shoot when manualy racked 2. it will not shoot after first round fired 3. it will eject and chamber a new round 4. it will not cock hammer when shot 5. it will cock hammer when you manualy cycle the bolt 6. it will lock open on last round. I was thinking that it was short strokeing, but it will hold open on last round. I was also thinking that the sear spring was weak and the hammer was jumping past the sear before it had a chance to engage. Any thoughts would be helpfull. Thanks Fisher King.