Hi All!
Long time lurker....new member! Hi! Finally made it out to shoot my factory Bushmaster 16" 450BM upper yesterday. All of the ejected casings have what seems like excessive black goo/burnt powder residue around the rim on the outside of the empty case. Ammo is Hornady Black 250gr. Shot 15 rounds and all look about the same. No damage to cases other than some scratches from the metal feel lips on the factory bushmaster mag. I haven't ever seen this or even close to it with any of my other calibers .556/.204/300BO/6.8. Didn't have any feed or eject issues, eject was at exactly 3:00, accuracy was acceptable for my skill level, no can, carbine buffer. BCG was a little on the dry side, and the only change made to the upper after the factory was a Ross brake which came highly recommended by all of you! Any thoughts? Just need to break it in? Over/under gassed? Sloppy chamber? I don't want to overthink it, just making sure I don't have a safety issue.