How to change a welded muzzle brake to a flash hider.
Bushmaster muzzle brakes and flash hiders that are permanently attached are done so in the following manner: The unit is threaded onto the barrel, blind hole drilled in two places into the threads, holes are pinned, pins are welded over, welds are ground flush and the complete barrel assembly is then sent to finish.
Free float handguards that replace the barrel nut can not be installed on these barrels.
In order to remove the unit without damaging the muzzle the pins must be drilled or ground to below the threads before removal of the unit. This will usually damage the flash hider or brake so that it can not be reused. The threads of the muzzle may still have some damage that would require chasing with a die before replacing the flash hider or brake.
In order to bring the barrel back to legal length the replacement flash hider or brake must be long enough to bring the total length to 16" or longer overall length. It must also be permanently attached according to BATF standards by high temperature silver soldering or pinning and welding. An A2 bird cage is not long enough to do that. The Phantoms and Izzy flash suppressors are long enough.
Bushmaster is not set up to do individual piecework on barrels so it would need to be done by a gunsmithing shop or a machine shop.
If you want to interchange muzzle brakes and suppressors you will need to get a pre ban type 16" barrel.