Know somebody that had a 2 3/4" over and under opened up to 3". Also know a couple of people that have 2 3/4" rem 870 and put a 3" barrel on them a shot 3" like a single shot for turkeys. They have to pump real hard to eject the shell or some times have to cut it out. They mainly did this when 3" guns.where not the norm and most shotguns where 2 3/4 and they got the barrel cheaper then a new gun. I would not recommend it but they never had a problem.