You can have a muzzle brake. You can’t have a flash hider and you can’t have a muzzle brake the is also a flash hider (rare but hard to come across) You have to be able to prove usually via paperwork from the manufacturer that the item is a muzzle brake only if it ever comes into question. On top of all of the the muzzle brake has to be permanently attached to the barrel be either welding it directly to the barrel which i dont recommend (looks like shit and the heat can warp and ruin the barrel. Typical you adjust them until straight on the barrel then you drill the muzzle brake and install a roll pin which is then tack welded so the it can be removed and the muzzle brake can’t be wrenched off.