I have a Model 11 I bought as a box of parts. The guy told me it was his deceased FILs quail gun and I shouldn't fire it. I got it home (bought it around 1030-11PM under the lot light of a car dealership
) and inspected it thoroughly. I noted that the only thing missing on this basket case shotgun was the heavy friction ring and a tiny keeper screw. The buttstock wrist area was cobbled together with a spacer block of wood and friction tape. I re-assembled the gun and was shooting it the next day. I didn't clean it, just oiled it.
He said it was unsafe to shoot because it had a slight dent in the barrel from where his FIL slammed it in a car door decades beforehand. It didn't effect anything. Shot like a champ! The barrel had already been cut down in the past anyway.
I took it apart completely. All the way down to springs, pins and screws. This gun was
CAKED with a mix of old oil (3in1, WD-40, Whale oil - who knows!), carbon, dog hair and quail feathers.
CAKED! I scraped it all out (it was like hard clay) and brushed everything out. I took the entire fire control group apart and the bolt as well. It was a job. Got it all put back together and it finally would "ring" when you closed the action vs. a dull "thud".
I bought a "semi drop-in" stock from Brownells, the keeper screw, friction ring and magazine spring. Fitting the stock was interesting to say the least. I cut the barrel to a legal length and re-soldered a bead on it. The whole gun is plum brown and I didn't touch the finish.
I called Remington to check the age of the gun and it was made 1914. It has had a life for sure. I shoot the living fool out of this gun and anyone who shoots it loves it. I paid $60 for the gun and about another $80 for parts. I like it.
To the OP, don't fear taking it completely down. It will allow you to appreciate the mind of JMB.