A Cartridge stop is a 5" stamped piece of metal that is part of the receiver mechanism. It has complementary stamped piece of metal on the other side called a cartridge interupter. Both these pieces fit on the inner portion of the receiver housing. They are not screwed in or bolted down. The shell elevator cycles between these pieces.
The cartridge stop, basically like its name implies, stops the next shell in the magazine tube from advancing once the elevator chambers the current round. If it malfunctions (ie is bent), two things can occur, either the shell will not advance and stay stuck in the magazine tube, or all shells in the magazine tube will fall out at your feet. Either way a pain.
Last edited by Southwest1; February 15, 2013 at 11:39 PM.