Posted on September 11, 2017 by Autumn Stewart.300 Blackout SBR View this post on Instagram New .300BLK upper on the SBR. Great present to celebrate a new job and anniversary. On the search for an optic, but the flip up sights will work just fine. #ar15 #300blk #runandgun #aimsurplus #magpul #sbr #shortbarrelrifle A post shared by @ keenan_shoots on Oct 22, 2016 at 1:41pm PDT PHOTO CREDIT: keenan_shoots << Go and Subscribe