interested in buying a bushy M4 with a3upper, just wondering usual price and is it better to just build gun. what is the quietest muzzle brake you make. if i ordered the gun could i get a different muzzle brake permanently attached or is it just the ycomp. if i got the actual 16in carbine gun could i have a muzzle brake put on at the factor. what comes with the gun when bought. thanks alot. wont buy anything but bushmaster.