This stuff works really well!
Tried it over the weekend on my DA Mask HD. Had a lot of rounds through it, not sure how many, but it was at the point where the baffle stack couldn't be pushed out anymore. After soaked for around a day in part A, they just slid out and a lot of the carbon was mush. Rinsed it off and scrubbed a bit with a plastic brush. There were still a lot of hard carbon deposits all over it. So, I soaked it again for a day in part B. When I opened it this time, a lot of carbon crumbs fell out. It was around 90% clean, but still had some hard deposits. So, I did another round of each. After the second round of part B, the can looked brand new.
I was re-using the solution, just adding a bit to top it up the second time around. Still worked great.
I wouldn't bother with it on a can or parts that are CLR safe (I know the Mask is, but wanted to try it on a really dirty can). It's great for parts you can't use CLR on though. Betting it would clean muzzle brake really well too.