I was gifted a very old and worn Winchester Model 12. It must have had some regular maintenance because the bore is spotless but the exterior shows lots of wear. I test fired it with a low brass circa late 1960's Remington bird shot as well as two (new) NSI low recoil 00 buck. The buckshot has what I would call 3/4 high aluminum base. All 3 rounds chambered smoothly and fired just fine but each empty casing became stuck in the chamber to the point that it needed to be poked out of the chamber with a cleaning rod. I wire brushed the chamber and tested the empty casings and they still stick in the chamber. I don't know where to go from here. Is this thing just shot out? It's been more than 50 years but when I was a kid I fired 1000's of rounds through a number of shotguns and never came across a problem like this. Any suggestions would be appreciated. Thanks Steve B