Today I put about 450 rounds through my new mp40 and I did not experience a single malfunction. I sold my s&w 40gve at last weeks gunshow to up-grade to the mp and I couldn't be happier. I never had any problems of any kind with the sigma I just got rid of, I just couldn't get used to that stiff trigger. The MP shot like a dream compared to the sigma. I tried out all the grips and sevral diffrent kinds of ammo. The Medium backstrap seems to work best for me. I was really suprised on the recoil it was not like most 40 cals I have shot. Overall I was very pleased and look forward to getting back to the range.