Gas tube hole in is fsb too small - Luth-AR 5.56mm 11.5in Lighweight Barrel w/FSB

I. don't know how this is to be, but the gas tube hole in the FSB is too small. After I had the barrel assy on and barrel nut timed, the gas tube wouldn't slide in. I had to remove the FSB and tried three different gas tubes....none fit. The remedy was to turn the gas tube down a few thousands with sandpaper to get it to fit enough to line up the pin hole. Barrel shot decently with SS109, but the barrel isn't quite lightweight or Gov't profile. Not sure what Luth-AR was thinking when they make this barrel. Finish was decent and even.