NahlaDoc

I have run about 50 rounds through my new Benelli M4 and still have problems cycling low recoil loads ( slugs or buck) . The shells do not fully eject out. Anything under 1200fps does this. Is it necessary to run the high powered rounds through first and if so, about how many?? I already sent it back to Benelli once and they returned it with a lame excuse that it was the Strike Industries Hayl Rail I had installed. So i put the original hand rails back on and guess what- same issue. ANybody with advice???? Thank you.