I have this old Winchester Model 12 shotgun that I use for some shooting games and it has been remarkably smooth and reliable, until today. After chambering and firing a round, the bolt stuck closed. This happened a few times and I was able to depress the bolt release button and eject with some force. Upon fiddling with it and dry firing some, I have totally locked it up. Bolt is stuck closed, hammer down, firing pin through the breech face, and bolt release button stuck in. Any words of wisdom? I own newer guns but none are as cool as this old Model 12 (when it runs).