Len, I just finished building my custom .388 ultramag that I had Krieger install a Vais brake on. Gun weighs 11.5lbs. For comparison I have a Weatherby .300mag, Laminated stock that weighs a good 10lbs, with the Weatherby accubrake installed. The accubrake has 5 sets of hole as does the KDF, not sure the difference in the internal design. Shooting the .388(Vais) with 250g Siera SBT @ 2900fps, without gripping the gun with both hands, I'd say the recoil is slightly more than the Weatherby shooting 180g Partitions. As for the noise, the Vais is definetly "quieter" than the Weatherby. Then again that might be cause the muzzle is in the next county due to the 30" barrel
I also installed a Vais brake on a .300 ultramag BDL, tamed it down to where it's pleasant to shoot.