T3x, 7 Mag, 1/2-28, Area 419 Hellfire, self timing.
Running 160s with 70 grains Retumbo, recoil with brake about like a 257 Roberts running 85 grain bullets..
Didn't know they sold brakes in that thread pitch/bore diameter. My 270 is threaded 1/2-28 and that might workout.