I'm having same same problem in both models of the Remington semi-autos. After one or two shots the bolt goesinto slow motion and fails to feed the next shell. Someone said that it was the "O" ring needing replacement. I checked both shotguns today and the rings seem to be OK. Anyone have any suggestions. Thanks in advance.

They are pretty simple. Have shot an 1100 for years.

O-ring still good - first thing to check. I think they will actually cycle without one, if the rest of the action is clean enough (so says my dad and knowing him he probably tried it).

Clean any/all crud off the outside of the magazine tube, and the inside of the 'carrier' mechanism (for lack of a better term) where it rides over the mag tube.

Check the gas port(s) in the barrel for blockage, but I've never seen that happen. 1100s have either 1 (3" chamber) or 2 (2 3/4" chamber). I think that 1187s have two ports, regardless. Take a small drill bit and very carefully, BY HAND, twist it around up inside the barrel ports. Just use the flutes on the drill bit to clean the insides of the ports - if necessary.

Last thing.... after enough shells, the recoil spring assembly that goes into the buttstock will gum up. Quit using Red Dot in light loads years ago when I took one apart and found it full of little bitty red flakes. To be fair, there's not telling how many thousands of rounds it had shot since last being cleaned. Still I've never had this happen again when using 452AA/473AA (both discontinued) and their successors, WSL, WST, WSF, all Olin powders.

I have taken apart 1100s for people who hadn't cleaned them in a decade, and they were still working.

Good luck - it's pretty much got to be one of those areas, unless it's something really strange like a piece of grit or burr on the action rails. But you would probably have noticed that.

Oh and don't oil the outside of the mag tube, except very sparingly. That will just make more fouling build up. I wipe it down wiht Hoppe's #9 and leave it at that, never had any rust problems.