About 6 months back I bought a 686 off of a friend who had never shot it. This is my first handgun Being that I'm in school I haven't had much time to shoot it. However the few times I have made it to the range, it seems that after every 12 shots or so the extractor rod unscrews making the cylinder stick in the frame when I try to extract the spent cases. I find that I have to retighten or turn the extractor rod really often. Is this normal? Is there anyway to keep the rod from unscrewing?