Don't forget, fellas, the recoil the .338 Lap Mag has that makes it very hard to shoot accurately when fired off ones shoulder happens before the bullet clears the muzzle and a external brake will then reduce the remaining 90% of the recoil. By the time that muzzle brake reduces felt recoil, the bullet's already many, many yards down range.
It's the recoil while the bullet goes down the barrel that moves the barrel off where it pointed when the primer flashed and started burning the powder. That much recoil is hard to manage exactly the same for each shot.
Few people can manage the recoil of a 13 pound .22 rimfire match rifle and shoot no worse than 1 MOA at 50 yards. That recoil during the time the bullet goes down its barrel lasts 3 times as long as most centerfire rifles. Doesn't matter that it kicks a whole lot less than a .338 Lap Mag; people have a hard time holding perfectly still for 3 to 4 thousandths of a second while that 40 grain bullet goes down and out the barrel. That darned pulse beat pumping blood into our muscles makes them swell and shrink a bit 60 to 100 times a minute and that's transferred to the rifle we're holding.
Why do you think the 6.5x.284's popular for replacing the 30 caliber magnums formerly the favorite on long range matches fired slung up in prone? Barrel time recoil.