I have three grizzly gunworks brakes, they make clamp on and thread on. Super happy with all of them. A buddy has the Defcon 1 that ggw makes on a 308, you don't lose sight picture at a 100. He put a ruger hybrid brake on his Bergara 6.5cm. We could hardly notice the difference in recoil. The 308 has noticeably less recoil than the 6.5.
I'm going to try the area 419 brake on a rifle I'm having rebarreled as another one to check out