The KDF brake is not really all that effecient. Three brakes that some to mind are far better in recoil reduction and noise.
The Answer brake is the best so far for recoil reduction and is not as nasty loud as a KDF.
OPSINC brakes are very good for recoil and vent gas to the sides. They work better than the KDF for recoil.
Vais (Bartlett) brakes are much less offensive and also are better for recoil reduction than the KDF.
I have installed litterally hundreds of brakes over the years. I have cut more KDF brakes off than any other to be replaced by a better brake.
Other pluses about the Answer and Vais brakes are that they can be tuerned down and blended in with a barrel to make it look seamless. The will look like part of the barrel and not some big ole pickle on the end of your rifle. The OPS INC brake can be turned down as well if the barrel brake OD's are close.
I must comment on the two guys that said they didn't find shooting the brake without ear protection objectionable. I ended up shooting mine without hearing protection during an elk last winter. IT WAS A BIG MISTAKE!!! My ears rang for hours and I KNOW I have contributed to my continual tinnitus. I now shoot it without the brake when hunting, added a thread protector. If I KNEW I had time to stuff in plugs I'd consider hunting with the brake. Our sit and glass approach to coues wt could work with the brake.
I will say the brake is very effective and kind of sexy looking compared to that bulbous thing KDF makes.