I own several guns with a Vais brake installed: two 7mm RSAUMS and one 300 Win Mag. They definately reduce recoil (how much exactly, I don't know, but enough I enjoy shooting them with a brake and not really without). two of the three afore mentioned guns are lightweight hunting guns and one is 17#s. I have shot with and without the brake installed and have not seen an accuracy change. Which plexes me because you are adding more weight to the end of the barrel.?! All brakes (besides suppresors) are quite noticeably louder, not sure if the Vais is quieter then any other. I agree with the statement that the installation is crucial. I have been told that the bigger diameter (OD) the better for reduced recoil. I would suggest calling Vais and talking with them. Once installed you can always take it off to get a "feel" for reduced felt recoil and re-install it (also for accuracy changes) and if you decide you don't like it, just have the gunsmith cut the threads off and go back to a standard muzzle (minus about 1/2"). Good luck and have fun.
Edward