A lot of different 11-87's out there. First off the "sportsmans", I don't know much about, but are cheaper versions of the real 11-87, not sure why they even did it, I guess for the cheap retailers to compete. Kindof like buying a "john deer" tractor at home depot, it's not the same tractor you buy at the dealership, much cheaper.
I have a 20 some year old 11-87 and a 10 year old one, both are considered the "special purpose" model. I am super hard on the 20 yo gun, and have been. Stopped working well about 5 years ago, cycling issues, etc. I had never "totally" cleaned the gun, main spring was like a solid piece of rust, and had weed seeds sprouting in it. Cleaned it out, replaced the spring, and havn't done a thing to it since. Plus of course the typical clean your gun stuff when shooting dirty shells, so the ports don't get gummed up, is common with the 11-87's.
As for the "O" rings, I had big problems with my new gun always breaking them. The problem in my opinion was the piston rings. At some point Remmington changed the piston rings, becasue my older 11-87 had 2 piston rings, one was flat, it went on the tube first, then the other one had a curved edge and just sat on top of the first one. The newer gun, had 2 piston rings as well, but one "snapped" over the other one, then was put over the tube. I think the newer piston rings were my problem, as I ordered new piston rings from the factory, but I ordered the ones that are shown in the 1100's parts list, which were the same as my older gun, and haven't broke a O ring since. Just my observations with these guns.
Bottom line with these, are if you really want a 11-87, try and find the special purpose guns, and stay away from the sportsman model.