either it is gummed up a bit, and not striking the rim hard enough, the pin is chipped, or the chamber is peened. One of the three.
take out the bolt assy., and thoroughly clean it out, with a soak in brake cleaner for a day or two if you have to, then blast out with a hi speed water hose. then blow out, and lightly lube, with a very thin electronic type lube.
If still no worky, then problem is either one of the other two. the bbl being loose is a new one on me, but then, I do not know much about working on winny 22's, allthough that one is supposed to be highly reliable.