A couple of years ago I bought a Colt 6551 postban upper to put on my Bushmaster to get that A2 profile barrel. They say Kurts Kustom does a really terrific job of turning a HB down also. Lots of options till Bushmaster has them. You could always buy an A2 preban barrel assembly from Bushmaster, have someone or yourself put it on an upper after grounding off the bayonet lug and permanently attaching a break or cutting off the threads and crowning the muzzle???