I currently have a friend's Winchester 1901 10 gauge lever action shotgun, to clean it up and try to see if it can be fired. It's in really good condition especially since it was made sometime around 1902 and is ~110 years old. The part that I can't figure out is what length of shell it was designed for. I've read a couple different things online, but sources don't seem to agree if its 2-3/4" or 2-5/8". I'm not sure how to measure it since the only measurable base point in the barrel is the forcing cone, and that doesn't start till after the crimp folds have expanded. Does anyone know much about these guns? Anyone have some ideas on what I should look for to get some shells and shoot it?