I sent my M3 back to be fixed (Free Warranty work). It was returned fixed, but no repair explanation was given. To me "it seemed" like the bolt was caching on something it would stick just a bit, but after the repair the bolt working smoothly. Now the M3 will cycle with very heavy turkey loads. I have not found any 00BUCK loads heavy enough to cycle, but I only tried what my local store had. If you have a specific brand of 00Buck shells that work in your M3, please let me know. I would like to try them in my M3.