Update. I did a search before making this post but I searched on "AR cutting barrel" and didn't get any hits. I just found a recent post that was labeled "Threading barrel for silencer" or something close and I think I found what I need. Saw in there a recommendation to go to BP Tactical. Sounds like they can do exactly what I want and very reasonable. Would still like responses for anyone that actually had thiers cut down and any changes in accuracy.