The problem could be a combination of gun and shells being slightly out of spec. I had a problem with an Ithaca NID in 16 ga. I had shot it with no probllems with some shells I had on hand, but needed more for dove hunting. Went to Wally world and bought 10 boxes of Winchester field loads (the only type available). Some had silver colored heads and some werebrass colored, but the boxes did not indicate any difference in the loads. One color head would work, but the gun couldn't be closed on the others. I did some measuring and found the rim recess on the gun to be undersize, and one color of heads to be oversize. When combined the shells wouldn't work in that gun. I opend the rim recess to standard diameter, and had no more problems with any shells.