Anything you hang on a barrel will change the frequency it vibrates at. Doing so may or may not change its accuracy. But the only thing that'll change is the barrel's resonant frequency and its harmonics; they'll still stay fixed for every shot fired regardless of the loads power; lower frequency for flimsy barrels, higher frequency for stiffer ones.
There's no accuracy difference between whippy, skinny barrels and stiff, thick ones. And many times a short, skinny barrel will be stiffer than a longer, thicker one for the same cartridge. If a load won't shoot accurate in a barrel, it's not how stiff or rigid the barrel is; something else ain't right.
Glue a large nut or two to the barrel just behind the muzzle then see what happens. Move the nuts back and forth to see if there's any difference. That's cheaper than a muzzle brake. You can accomplish the same thing by changing powder charge weight to make bullets exit at a different point on the muzzle axis vertical swing to improve accuracy.
US Navy Distinguished Marksman Badge 153
Former US Navy & Palma Rifle Team Member
NRA High Power Master & Long Range High Master
NRA Smallbore Prone Master