Hey. I'm an older fellow who has taken up a new career in smithing. I have an old Stevens 11b that lets a shell extract from the mag as soon as the gun is fired causing the gun to jam. I've replaced all the old springs. I've tuned the slide release spring and replaced the shell stop. While the shell is in the mag up against the shell stop their sea to be a lot of slop. I've tried to adjust the stop to compensate for the slop to no availe. As soon as the gun is fired the shell slips in under the stop. I put a stiffer spring in the shell stop and the gun still fails. Any advice or suggestions.