I finally finished an AR 10 upper project for gunsmithing class I started last fall. I acquired all the parts - Aero upper, Green Mountain barrel blank, etc. 6.5 Creedmoor caliber. Classes were stalled early last spring so things were delayed. All went well until firing. Using Barnes 140 gr. BTSP, the bullet jams against the end of the barrel between the extension lugs. I'm wondering if that particular bullet is too long for that upper and a shorter bullet would let the brass ride up the feed ramp correctly. If I seat the bullets much deeper the ogive is in the case mouth. Seems to shoot pretty well except for being a single shot. Any thoughts?