I have two 1100's but both of mine are 2 3/4". Not sure how old you are talking but shotguns that are chambered for 3" should be able to eat 2 3/4" as well. This might be too obvious but have you broken it down and cleaned and oiled it? I've never had a problem like you are experiencing with mine and I have shot thousands of rounds through my 1100 Trap. Sorry, I wasn't more help.