The upper is a PSA AV-9 with a BYOAR AR-V MP5 clone forearm, the lower is a New Frontier Armory C5 that takes MP5 magazines. I'm thinking of doing an AR10 in this configuration to go along with my HK51.
I have not been able to log in to eforms.atf.gov for 2 days now. Is anyone else having issues?
I've got 3 new pieces I need to Form 2 but I can not get logged in...
I build my 51 bolt carriers like Vollmer did, they are cut to 4.140" in length and then I use a shortened 93/33 cocking support. It looks like your bolt carrier is cut the way PTR cut's theirs.