TLB2: pic is not too clear of fired brass. Take the guts off the barreled receiver, use a penlight to examine the chamber. Take more pictures of the fired case - if the chamber is rough - the fired case should show an "orange peel" pattern. You can try to polish the chamber walls with 400 sandpaper but don't touch the shoulder or chamber neck. Take it to a reliable gunsmith if you are not comfortable doing the above. M100 chambers are like M742 Remington chambers - no one cleans them and they get pitted and the extractor tries to do it's job and pulls the rim off the fired case which has expanded into the rough chamber upon firing.. Remington makes a chamber brush to scrub the chamber and it should work on the M100. Is the owner shooting FRESH factory loads or hot reloads or old ammo that was subject to high temperature in a hot car? That could be the problem. If not - you have a parts gun!Good luck with it, Mel
