Rifling twist must be done on the inside. Your only other option is to turn the barrel inside out.
Are you saying you need to turn it inside out
first, then twist it with the pipe wrenches to change the rate of twist, and then turn it inside in again? If you have pictures of the process, please post them. How far should I turn the wrenches to change my .45's twist from 1:30 to 1:16.375?