We tested the effects of bullet-brake radial clearance on ballistics. In our application, we found that smaller clearances would more likely induce yaw on otherwise stable bullets.
The assumption is that asymmetric alignment between the bullet path and the brake's circular hole left an asymmetric layer of muzzle gases about the bullet. That would lend to an asymmetric force about the circumference of the bullet, which would presumably induce yaw.
We also found that increasing the distance between the muzzle and the brake hole reduced the likelihood and/or amplitude of yaw. Apparently, removing muzzle gases from the bullet at a point where the muzzle gases are less dense reduces the amount, if not the distribution, of asymmetric forces.
That said, in our application, we determined Goldilox zones for 30-cal (0.348"), 6.5mm (0.302"), and 6mm (0.281").
Please note that these "zones" presume alignment with machining tolerances common to many quality barrel manufacturers. Also, know that the "muzzle brake" hole in our device is much farther from the muzzle than a dedicated brake. Given that your brake is much closer to the muzzle, it would follow that a 0.331" hole on a high-quality brake installed on a properly prepared muzzle would be just about right for a 30-cal round.
If you're suspicious about the barrel/brake/caliber combination, use an alignment rod (Brownell's has them) to check concentricity. Punch holes at ~50 yards and 100 yards to check for yaw.
