I turn the nut on the barrel end. To protect the barrel, I now put an AMD65 barrel extension and two washers on the muzzle end. You probably dont need the barrel extension, but it keeps from pressing on the muzzle. An AMD65 or Krink muzzle break would also work.
If the going gets tough, the muzzle end nut may gall and bind. At that point, the all thread starts threading into whatever you use at the trunnion end.
I really think using the carrier is better than using a block on the trunnion end. It places the pressure exactly where you need it. You may be worried that you will hurt the carrier. I really dont think you will, but that is your call of course.
No matter what happens, somebody will find a way to take it too seriously. ~Dave Barry, Dave Barry Turns 50