It helps to have a set of aluminum soft jaws that have a round profile to them, then you clamp the barrel in the vise, close to the flash hider and take it off.
Another option is to use two pieces of wood and clamp the barrel, then remove the flash hider. I've found the wood won't mar the finish, the aluminum soft jaws need something in between, like a piece of cloth to keep the finish from getting marked up.
It's always best to clamp something as close to where the work is being done, less chance to bending or breaking anything.
And always use "feeling" when removing or installing items on a firearm, nothing is worse then have that sinking feeling that the part you are trying to remove isn't moving and something else is. Or the threads are starting to let go. It's good that you stopped, since it didn't "feel" right.
Slots at the end of the barrel to facilitate a wrench for installing and removing muzzle devices, good idea, not sure why they don't incorporate that into the design??
Hope this helps
