Have you given it a good cleaning? I mean an Army type cleaning! Take it apart and take it and your cleaning gear into the shower with you. Get allof the gunk out of it. Hot water is about the only thing that will clean cosmoline out of the nooks and crannies of a firearm. And believe me when those guns were shipped here they were coated in the stuff. Check the gas holes, make sure that junk isn't in them. Then dry it off, lube it and take it out for a try.