Hello All, I hope one of the experts here can help me. I have a Winchester Model 100 semi-auto that was given to me by my late Father-In-Law. I fired it a few times with regular Remington factory ammo and all was normal, then it stopped firing, and in the next 10-20 attempts it only fired once. I took it to a gunsmith who had it for a year and he replaced a few parts and after about a $100 repair bill I took it back to the range. It fired once and that was it. I noticed through all this that it appears something is going on with the end of the slide or bolt and so I took the gun back to my gunsmith, who had it for another year. I finally asked what the deal was and he said he had no idea what to do next, that one person had suggested it needed a “new gas system”, but he didn’t seem too sure of this being a cure. The attached picture shows more clearly than I can explain in words what I am seeing when it fires vs. doesn’t fire. Does anyone have any idea how to fix this gun? Thank you in advance for your consideration.