Hello I'm new to the forum. I have done research through reading others posts for information. I have a 12 ga. Model 12 I've had for a few years and my dad has shot a M12 my whole life for trap. I've hade a model 12 20 ga for about a year now. I had bought it basically as a parts gun. It was missing trigger assembly, firing pin and a few other parts. I did have the bolt with a few parts on it. I bought the parts I needed to make it a shooter. I should say it's a 1927 era gun and well worth saving. So the problem I had was it would fire and then not fire. I put it away for awhile. I was researching head spacing and if it could be adjusted etc. Or if there was something else to address. I came across a thread from 07' that was very helpful. It dealt with the bolt and the wear issue in the receiver. So the next day I tore into it again to check things out. So i can feel a ever so slight edge in the receiver that the bolt can hang up on slightly. The bolt has a good edge on it. I' m also thinking the trigger group is out of a later model 12 and seams to interfere with the fore arm link to the bolt. It hangs up with it making it hard to put the gun back together. with all of this gong on I think it interferes with the bolt settling where it should to fire correctly. when installing the bolt it fits and locks in good. But all together it doesn't I guess. But I finally found that if I twisted the fore arm slightly to the left the arm put pressure on the bolt putting it in position and it fires. With all this said. I'm not looking for a perfect gun.And I'm not a gunsmith. I'm having fun looking at things from history and making them work. I admire what our forefathers came up with so long ago with pretty simple tools compared to today. And I just love seeing a gun shooting rather than being torn apart for parts. Thanks for reading and would love any input.