I have several of Ross brakes as seen in previous posts, but needed something special, a muzzle brake for my PTR-91.
The PTR-91 .308 and other HK G3's and clones use a 15mmx1mm thread pitch, which Ross doesn't do. So I had Ross make me a brake to my spec's, the rest of the work I did on my milling machine, etc. I wanted to tame the recoil of the PTR for quick follow-up shots when I use it for hog hunting.
I had to first tap the brake with the 15mmx1mm RH thread, and then I had to machine a non-threaded area on the back to slip over the raised portion on the PTR-91 barrel end.
Here is the end of the barrel on the PTR-91, same as other G3's:
Here is a pic after threading and machining:
then I turned a crush washer to mate the brake to the barrel, I was originally golng to flush it up to the barrel, but decided turning a crush washer was a better option so that the brake stayed tight and true.
I blasted the brake and finished in black cerakote (bake-on)