crewdog03

I have a 1972 Magnum Duck gun that shoots wonderfully. The only problem is it won't auto reload the next round in the magazine. I'm sure it's not a gas problem as the spent shell always ejects and the but more than half the time the bolt locks back and won't load the next round, as if the gun is empty. I've only tried Federal 2-3/4" shells, of different loads. I'm thinking it may be that it is either a spring issue or a shell issue. The gun was designed for 3" shells. I'm wondering if using a 3" shell would solve the problem simply. The only issue there is cost of shells since the 2-3/4" shells are considerably less expensive at my store. Any suggestions on fixing the loading of the subsequent shells?