I'm in the market for a new tactical semi-auto 12G shotgun. I currently have a Remington 870 Tactical that I'm hoping to trade or sell to get an auto loading shotgun. The most difficulty I am having is finding a model that can shoot 2.75" shells and 3" shells without having to change parts on it. It would be nice if there were one that fired 3.5" as well but it at least needs to shoot the other two. The other condition is that I am looking for one under $600. If anyone can point me in the right direction, I would appreciate it.