I recently bought a new 870 Express 12 gage. I took it to the dove opener this year, and it was the first time I had run some shells through it. My question is that on 3 or 4 occasions, i couldn't eject the shell after I had shot (I lost out on a bird because of it). I had to stop, and really force it to eject. I was using Federal shells. Is this because the gun is new, or is there some other problem?