I LOVE Remington 1100 shotguns.
The below info only refers to 12 gauge guns. I don't know about all the other style and calibers that they were available in. This is just generally speaking.
The 1100 used to come in two flavors. The regular 2 3/4" chamber gun would shoot ANY 2 3/4" shells. The Magnum was chambered for 2 3/4" and 3" shells. It would NOT function reliably with light 2 3/4" loads.
The 11-87 was chambered for 2 3/4" and 3" shells and is SUPPOSED to function with ALL loads due to it's new self-compensating gas system. (It usually does, too).
I've had three 1100s and one 11-87. I sold the 11-87 only because I had a chance to make some money on the deal, and the 2 3/4" 1100s do everthing I want my shotguns to do.
I have never had an O-ring break and have only replaced one on an older 1100 that I was having refinished. (The gunsmith talked me into it.)
"I AM my brothers keeper."