And if it doesn't get blasted out like bullets, the JB Weld will be hard to get out. I've used it to fix gouges in gasoline engine cylinder walls. It will last a long time. I've also removed a badly applied JB Weld fix on a gouged cylinder wall. Had to keep a torch on it till it was smoking hot and I was really worrying a bit about cracking the cylinder wall before it softened, becoming white and chalky. It sets permanently and can't be dissolved.

If your muzzle break is a screw on model, here is your solution. You can see George Washington's nose twitching because he appreciates quality.
JCN

George Vais made that for my girlfriend's 30-06 last week. He puts a knurl on them so you can screw them on and off more easily. If you send your KDF brake to him he can make one for you. The price is very reasonable. Turn around is fast also.
contact Information:

George Vais
High Tech Gunworks
182 South Cole Road
Boise, ID 83709
(208) 323-7674

George designed the Vais muzzle brake several years ago, then sold the rights to Ron Bartlett down in Texas. George was going to retire to Greece, but he's back in Boise now.

I have an older model 77 Ruger .338 that I had a KDF muzzle brake installed on many years ago. A couple of years ago I had a threaded cover made for the threads when the muzzle brake is off, but it's not NEARLY as neat as the one in your photo. What brand is it and how do I get one? Greg

Tape won't work, and you have to be very careful if you decide to plug the holes with any compound. The internal diameter of a muzzle brake is larger than the internal diameter of the muzzle. They are made that way so that the bullet does not hit the brake on its way out.

If you live near Cabela's or any other gun store, buy a set of electronic ear muffs such as Peltor's Tactical 6S or similar, and go hunting. If you can't afford that, then buy a few sets of foam ear plugs, and wear a set just before you fire your rifle. It's a simple as that.

One more reason to NEVER get a muzzle brake installed.

There are other ways to soften recoil. If they aren't enough, get a lighter recoiling rifle and learn to shoot better.