Well since I didn't feel like submitting a Form 1 for my braced Colt SMG clone, I decided to pin and weld a fake XM177 flash hider onto the barrel. With a 10.5" barrel, crush washer and fake flash hider, the OAL comes to 16 3/4" inches. I had to use a 1/8" end mill since there is not very much material between the threads and bore. I used a crush washer since I had extras handy and did not have the proper grenade ring.