I have attached a couple of photos illustrating an issue I recently had with some 2011 manufactured M855. The photos show severe bullet setback in the case upon chambering the round. There is a round of M193 shown for comparison purposes only. Fortunately for us, this caused a stoppage in the weapon. Had it fully chambered and fired the results may not have been good. The case mouth shows the typical 'grooves' associated with a case that has been crimped to a bullet's cannelure. I can only guess that the neck was not properly sized and that the crimp was not applied strong enough to fully keep the bullet in to place.