I've played with a lot of different brakes and my current favorites are the Terminator series out of New Zealand. I run a T4 on my 338/408 Improved rifle and a T5 on my 338/408 Improved pistol. This is an 18# gun shooting a 300gr bullet over 143gr of H50 BMG. The gun moves straight back about 2".

https://youtu.be/pQ6PEAWF5Zk?t=40s

Nothing I've played with is even close to be as effective as these brakes.