I have the same gun, I have never had problems with it chambering rounds. Are you drawing it back all the way? Or it could be the spring in the mag? If it is worn the shell may not be pushed up all the way from the spring, leading to it not catching. Is the gun new? If used, has it been cleaned well and lubed. Take it to a gun smith and see. B/c if push feeds, it sounds like it has something to to do with the low pick up of the case. Mag itself, not seated in all the way, something like that.