I have never heard of or seen a clamp on muzzle brake,that does not mean there are none. If there is such a brake installing it would not automatically mean you would loose accuracy. It could possibly not change anything, it could decrease accuracy, of it could enhance accuracy. It could act like a tuner .
AR muzzle breaks / flash suppressors are screwed on tight. Anything that is not mounted in the same way has a chance of vibrating and causing a problem with barrel harmonics. Usually the less contact of anything with a barrel the better.
There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.
Just curious Chesty Farmer, since the recoil of an AR is so minimal to start with why would you want to add a muzzle brake?
Not for an AR. I have a cousin who is going to Alaska with us. She is 5'3 120 pounds. I was going to set up a 30/06 for her. I did not want to go with managed recoil loads for caribou and moose. LOP might be an issue. And I might take off the recoil pad to help. So a muzzle break would be completely for recoil. For her size she is a beast. But I don't want to see her with a scar on that pretty face. My thought was if it clamps on I wouldn't have to go to the trouble and expense of threading a barrel that may never be used with the muzzle break again. And I don't want to sell it to her because it's my favorite gun. Shooting wise. Which is why I would not want damage to the barrel either.