Originally Posted by smle-man
I enlarged the diameter of my FH so a rifle grenade could not slip over it but be aware that when I spoke with DOJ about the modification they said any muzzle device that reduces the flash in any measurable way , even 1%, is considered a flash hider. They invited me to be the court test case on this but I declined. I guess the only way to be completely sure is to shoot the rifle with the modified device and without and measure the amount of flash in each configuration.
A wise and judicious approach.