I just went through this whole process on my .338 LM and solicited advice on this thread. You may want to read through that
thread at
https://www.longrangehunting.com/th...-models-of-muzzle-brakes-any-opinions.274176/
The most helpful sites that everyone quoted me so I could get actual hard evidence on percent of recoil reduction were these web sites.
https://muzzlebrakesandmore.com/testing-videos
https://precisionrifleblog.com/2015/08/21/muzzle-brake-summary-of-field-test-results/
One thing you have to watch out for is someone advertising an 84% recoil reduction but then seeing it was on a .223
and understand on the large rifles and magnums the percent reduction will be more like 40-50% or so. Also, small 3 port
brakes aren't going to perform like 4 port or 5 port brakes that are larger. You will see that in the testing videos.
One final piece of advice. I ended up selecting the 5 port super beast from MBM, and I wanted to use the ECtuner integrated with it. But, when I took it to the gunsmith, he took one look at my barrel and said no can do, because the barrel is fluted. and he needed more room than where the fluting ended vs. the muzzle crown to put in the threading for the EC tuner. So, he suggested a tapered ATS tuner that would fit and then the new brake on the end. There was only about an inch of room from where fluting stopped and the muzzle crown, so there was not room to integrate a longer length EC tuner in that set up. So, you have to take into account, barrel diameter, thread size and type, and fluting issues (because threading does not work well with fluting).
Nathan from Muzzle Brakes and More is a sponsor here on LRH too for your info, and its all made in the USA.
My other favorite from the test videos was the T-4 terminator made in New Zealand.
My own rifle is still at the smith so we'll see how it all works later.
Send pictures to a competent gun smith with some micrometer diameters at the end of your barrel to get the final advice.