I have a RRA LAR-8 (.308) Varmint A4 upper on order that's supposed to arrive in the next couple of days. I'm going to have my supplier ship it to ADCO to have the barrel threaded. However, I'm concerned that the .308 Varmint A4 barrel will have a larger diameter than the Vortex FH I'm planning to mount and whether I'd need ADCO to turn down the barrel to match the Vortex diameter. Anyone know what the diameter of a 20" Varmint A4 barrel is ahead of the gas block? I've searched RRA's web site with no luck, and I've tried to call them the past couple of days but keep getting a busy signal.