Ditto what shotgunjones said-a touch of rust in the chamber area can make extraction miserable as well. I have a 16 gauge that would rather not eat anything but brass base hulls.
Pull that stock by removing the through bolt, and remove the little screws that retain the big screws that hold the carrier and trigger group in. A gob of varnish-esque grease planted in the works can gum up the action in a hurry. Soak the trigger group in the solvent of opportunity (what you have around the homestead, usually-mineral spirits, lacquer thinner, acetone, unleaded benzene if you have access to a refinery down there) overnight, with a good toothbrushing (use your old toothbrush) and a blast or two of compressed air. The bolt can take the same treatment. You don't really have to dissasemble either of them.
Time frame should be overnight, money spent, slim to none. Let us know what happens.
Best,
Ted
