Having read many experts saying truing the upper receiver is a very good move, I ordered a kit that should be here in a few days. It has a machined insert, 220 grinding compound, and a flexible shaft to insert in a drill for power. I also have two DPMS Slick Side Uppers in route. The DPMS Slick Side upper is much thicker and will be more stable aiding dependable repeatable accuracy. The ARP 16" Scout barrels are here and I look forward to the seeing the accuracy they are so well known for.