I have had my Marlin since I was a teenager. I went a long time after I got that gun and never cleaned the bolt real good. The rest of the gun was cleaned like it should, but I just didn't think to clean the bolt. After a while, the dents on my primers starting getting more shallow to the point Igot amisfire. Once I cleaned the bolt everything was fine. Make sure your firing pin is good and loose inside the bolt. You would be suprised the dirt, grime, and dust that gets in that area.

If that is not your problem, I would say you have a mechanical problem that will have to be fixed.

C. Davis