There is no impact involved when I change a barrel. I apply pressure smoothly, using a rear entry action wrench that has a cross bar, and when the barrel is slightly loosened, perhaps a quarter turn or less, I remove the rifle from the barrel vise and remove the barrel by hand. When I am putting a barrel on, after applying a very thin layer of antisieze, I screw the barrel in by hand until it stops, put the rifle in the barrel vise, and finish tightening the barrel into the action. All of this is done with very smooth application of force. There is no stress to the scope since the wrench only engages in the front receiver ring, and cannot twist the action. Changing barrels that are not factory installed, with the proper tools, is really no big deal. The only reason that I would remove an action from its stock, or a scope from the rifle, to change a barrel, would be if there was a clearance issue. When I have used a port wrench on a benchrest rifle that had a glued in action, I supported the stock under the action with one hand, while I pushed down on the wrench with the other, so that the barrel was only seeing twisting force. The one exception to all of this is when a factory installed barrel is removed for the first time. In those situations, I take the barreled action to a friend who has the proper equipment to deal with the high forces that may be required, without damaging anything. Then I remove everything from the action, trigger bolt, scope base(s), and stock. On little tip...when I first started using my low torque aluminum barrel vise to work on my benchrest rifle, I decided that I needed to develop a system for limiting the torque that I applied to the four nuts that clamp the barrel. I had picked up a combination wrench to leave with the vise, and decided to tighten the nuts only as much as was possible using one hand, that was flush to the opposite end of the wrench that was being used. I have big hands, and have spent some time in my life twisting wrenches. That was about fifteen years ago, and the method has continued to work for me without a hitch, or slip.