Yeah, I can't get mine to budge, either. I have a 101S, and I don't want to damage anything...
Anyway, that's looking down the barrel, I turn to the right, if I want to loosen it? To be clear, if I'm to place the stock of the gun on the ground, and hover my head over the muzzle, the direction I'd turn the break, if I wanted to loosen it, would be to the right, right?
For the life of me, I find the fact that Arsenal would make it so tough to remove muzzle break to frustrating, at the very least.
ETA: I got my off using a meat skewer (two of them) and a pen to depress the pin. Oh, and all of this while turning to the right.
Off topic, there is a place that folks mention, from time to time -- "CDI" or something like that. No, it's not CDNN, or Atlantic... For some reason, I can't remember their name to save my soul.
Thanks for your help.