From what I have read the Rem 1100 is supposed to have an O RIng slipped over the mag tube. I just got an older 1100 and disassembled it for inspection and cleaning because the fellow from whom I got it said it was not cycling. There is no rubber O ring but rather a very slim metal ring which has a split in it.
Is the O ring or barrel seal supposed to be metal or rubber?
Is the O ring or barrel seal supposed to be metal or rubber?