A friend put one on his 270W Weatherby, with no other changes, it improved his groups from 1½ moa to 3/4 moa. I tried one it on a .243 Ultra and it made no change, but the rifle was already shooting sub moa, I guess it was asking too much of it to improve accuracy to less than the 1/2 moa it was already shooting, and I suspect that would be the case with BR rifles. For the $12-$15 it cost, it would be well worth it if it saved you from buying several different types of ammo for a non-handloader. I know I've wasted a heck of a lot more money on new products than that, that offered absolutely no return on my money!!
Tim