Ok, I'm currently trying to fix a friend of mine's Winchester Model 190 .22Lr Semi-auto. (Yes I understand it is an "obsolete" gun and is VERY VERY VERY annoying to ressammble.
That aside, The issue with the rifle is that when shooting, after every 2 or 3 shells it will fail to fire the round in the chamber. It will leave the mark of the firing pin but I guess it's not hitting it hard enough to ignite the primer. I know it's either the firing pin is worn down, the hammer is worn or the hammer spring is weaking but I'm not exactly sure.
Also, take into account that this rifle is probbaly older than I am.