We too all our barrel threading in-house. We indicate of the bore line not the OD of the barrel. The big difference is the accuracy! If you indicate off the OD of the barrel then you may end up with threads that are not center to the bore line.
In most cases its a 24hr turnaround time.
This service is for barrels that have the action or receiver already removed. Additional labor me be required to remove any action or receiver that is still installed on the barrel.