My Marlin 39a hasn't been extracting shells. It did this when I got it but a switch to Winchester ammo solved the problem. Now, about 3500 rounds later it fails to extract about once every 20 shots. I open the lever and look in and there is a shaved off spot on the rim where the extractor drug over it. Changing ammo brands again didn't help. I have carefully cleaned it every 150 shots since the day I got it and I simply don't know what's up. PLEASE HELP!
