I had a KDF varmint brake made up for my .338 Win Mag when I got it shortened to 23". I also got a muzzle cap. The brake did reduce recoil. subjectively it seemed similar to a .270 with 130 gr bullets.
I only used the brake a few times. They are obnoxiously loud and the blast on a covered range does not make friends. Hunting with one, everyone in the party has to have ear protection on at all times or they risk damage.
The brake is in my reloading die box and will stay there until I sell it or pass. A Decelerator pad and a McMillan stock were also added and seemed to help with the effect of recoil a lot.
