I am considering a M4 upper for my pre ban bushy. Will Bushmaster perm attach the phantom flash hider? If so which method do they use? Phil Dater from GemTech says that unless laser welded it will affect the heat trating of the flash hider and end of barrel. Ol Doc Dater is a pretty smart fella, so I am curious what method Bushmaster uses to perm attach. Any help is apprecated.