If you eliminate the extractor problem, and the gas ports in the barrel are not clogged - take it apart; spray everything with ether and wipe it down; check the recoil spring for signs of rust; check the magazine tube for a dent or high spot; clean the magazine tube & spring; and finally look at the chamber for rust & pitting.
I've always shot back bored barrels for ducks & geese and taken the time to polish the chambers to a near mirror finish (even if they're chromed). Use Fitz (sp?) polishing compound, a hand drill, and a bore brush wrapped with paper/cloth towel, using liberal amounts of polishing compound. Within 3-45 minutes your barrel should be ready for a good cleaning. Blow out and clear the orifice from the barrel to the gas chamber. Wipe down with WD-40 and coat all parts with dry-Molly Lube. Carefully Reassemble with the new or near-new parts; load with three shells, step out the back door and shoot - Boom, Boom, Boom!
When I hunted a lot - I use to never bring my shotgun into the camp, always leaving it in the truck, because condensation is the recoil spring's worst enemy!
Never oil your Rem 1100: WD-40 if wet, wipe it all off, and apply dry Molly Lube - always. And IF it's shooting - Boom, Boom, Boom - don't clean it unless you've dropped it in the water or filled the chamber and shell ports with trash! It ain't broke, don't fix it!