The Super 12 is designed to shoot any 2 3/4" or 3" without having to change barrels, flipping switches, adding or subtracting rings etc.
There were four different barrels 26", 28" and 30" Multi-choke barrels and a 22" slug barrel with rifle sights.
You can download the Super 12 manual from here
Model 3000 & 1000 Shotgun, 1500 & 1700 Rifle Manuals
KO