I think you're going to find several things:
the 45-120 is operating at a low pressure, which is going to make the brake much less effective
the 45-120 isn't a "long range" round, of course it can be done, but I still wouldn't want to shoot a ballistically inferior round that is still going to have plenty of recoil at long range
the 45-120 isn't "that" bad, and I think braking it will take out much of the joy of shooting it.
Just my opinion. If you still want a brake certainly get a baffle style one. One with 360 degree ports is less effective, uglier, and throws dirt.
The most effective ones are probably JP brakes, painkiller brakes from kirby allen, and muscle brakes. (google should find all of those)