The friend of mine got this piece with set of 3 barrels, smooth, combination and DR 308Win.
There was little problem with DR barells crossing point and MOA, but he fixed it just like that, but you have to undestand what'cha doing turning this screw at muzzle and check it every time by shooting. Don't forget to cool barrels before every regulating step.
Finally he got 1MOA at 100 yards from the first two shots and about 2MOA with six shots and no more, than 20 sec between every two shots.

Geno.