I'm not sure if you can help, but my father gave me his grandfather's Remington Model 10-A shotgun. It was pumping fine, but then he disassembled it to look down the barrel, and then put it back together. Now the pump moves back and forth about 3 inches, but doesn't pump down the entire way. It doesn't seem broke, just that he reassembled it incorrectly, and he can't remember how to do it. He's reassembled it many times to get it to work to no avail. If you can think of a step that he is missing, I'd greatly appreciate it.
Thank you for your time.