I already have .223 ARs, one with a 16" fluted Hbar, and another 20" Hbar (neither of which is chrome lined) so now I want something more "mil-spec"... thus the M4 profile, 5.56 chamber and chrome lining.
I have attached muzzlebrakes on FALs with 1100 degree silver solder. That works well, didn't affect accuracy in the 2 FALs I did, but did require refinishing the barrels / brakes. Plus, they are easy to take off... heat 'em up and twist. Of course, that much heat on a barrel still worries me so I might try blind pinning the Vortex.
I'm sure you've seen the CMMG (DPMS?) 14.5" M4 barrels, 1-7 twist with Phantom hider attached. That would work too, but I don't like the cast front sight base plus you're limited to the types of handguards (can't easily remove the front sight base w/ the perm. attached Phantom).
Scot