No specific experience with the Witt, but they are a top shelf co.
I have a similar design from Kahntrol that's been on my 7-08 for years, never an issue- never even had to re-torque the set screws. Precision machined to the taper of the barrel, they're not going to end up downrange.
Different animal, but ever tried to break a drill chuck loose from the tapered shaft? If the mating of the tapers is correct, there's a lot of holding power there.
BUT, here's the thing...
They don't say how much overbored they make the opening. Typically, this is from twenty to thirty thou over bullet diameter. With a clamp on, the brake is installed roughly concentric to the barrel, not the bore as it should be.
If the bore is not concentric to the barrel (and they never are, or threading a barrel muzzle would be much simpler), you may need greater clearance to avoid a bullet strike. My guess is, Witt uses a much more generous standard when reaming them to bullet caliber size.