It's BRAKE... as in "stop", not BREAK as in "broken"....
Anyway, Icarusp is correct. In a rifle, due to a combination of the relatively small bore, higher muzzle pressure, and higher velocity of the escaping gasses (escaping much faster than the bullet!), as well as the volume of the gasses, around 40 percent of the total measured recoil is from the leaving the barrel. Ouch... that's a whole lot! The principle is the same as the gasses escaping from a rocket engine, or what might be called the "nozzle effect". In a rearward deflecting brake, the issue is not only getting the gas to move in another direction, but also to allow it to escape in a manner achieves the most possible thrust through nozzle design. Generally smaller ports will be needed, and if you could shape one like a theoretically perfect turbine blade, you'd be doing pretty well indeed.
Lets say, for argument sake, on a medium caliber rifle, like the .30-06, where about 40 percent of the recoil is caused by the gasses.... the brake would need to totally negate the escaping gasses (which cannot be done, since some do escape in a forward direction), and have an incredible efficiency to overcome the gas inefficiency, plus overcome most of the remaining 60 percent of the recoil caused by the projectile. Not doing the math, the little Mr. Spock in me says "Highly improbable, Captain".
In truth, I've never tested the particular brake in question, but... have tested others of similar design. My impression those is generally the same as that of a "fart can" exhaust making your car "go faster" (through more power).
Recoiless rifles achieve their great reduction in recoil through the use of actual nozzles that deflect the gasses, tapped close to (or actually in) the chamber, at high pressure, and have a "blast zone" behind the operator that needs to be free of things you don't want hit with the considerable blast. Those will actually be thrust forward as the nozzles wear.