is there a recommended size difference between the bullet and the inside of a muzzlebrake that is added to a barrel. i have heard its a about 0.030 but i did not find any literature on point. i know of 1 rifle where this difference was about 0.012 and the rifle got alot more accurate after the brake was reemed a bit.

That would depend on who does the threading and how it was set up. Most "thread on" brakes have an exit much larger than needed to allow for axial misses between the bore and the brake. More common than most would think. You can imagine the affect on accuracy having the bullet flying off center through the brake, or, skipping through it... If both axis' are perfectly aligned then you can keep the exit at a minimum which I would expect to be at about .020 over.

I have designed and built Muzzle brakes in .375,8mm, 7mm and 6.5mm. The difference in brake ID and bullet dia. was arbitrarily held at .020" Never seemed to have a problem so never changed. I sold quite a number in the 90s to go on the threaded barrels of the 6.5x55s coming into the country. Never got an adverse comment. roger

I have installed quite a few through the years. KDF brakes recomended .016 clearance. Vais recomends .020 clearance and Shrewd specifies .020. There was a book on building and installing brakes that recomends .020

Some time back there was a fellow who did extensive testing on the subject and wrote a lengthy article on it. He determined that the ideal clearance was .020 and that when clearance was smaller than .016 accuracy dropped off. Also the more you went over .020 reduction of recoil started dropping off at an accelerated rate.

Another detrement to accuracy was leaving the bottom of the brake solid for recuced dust signature. Best being a radial symetrical pattern.

Most Weatherby factory brakes I have measured had about .040 clearance.

I've never understood spending $200 to devalue your rifle by $200, for a $400 net loss. However, this subject is much easier to discuss in a written forum than orally, for obvious reasons.

Every brake I do is .020" clearance and I have no issue. Stonecreek- some firearms are definatley in need of a brake, shoulder cannons of the magnum variety are usually on the hit list of brake worthy guns. I agree with you when all you are doing is going for a look but when it comes to function there is not much better than a brake to reduce recoil.

I'm not overly fond of being next to someone with a braked rifle. However, I have a break that cuts muzzle blast almost as effectivly as a suppressor! Measuring it I see I gave it o .010" clearance. I took it off and replaced it with a suppressor which didn't reduce noise as much as I had expected or hoped but is still quieter than the 'break' but not much longer - both being overbarrel.