I have a Blaser S2. And I am very keen of it. I use Lapua mega 285 gr home loaded. You can regulate the right barrel. But do not do that before you have regulated your sight for the left barrel. And do not change the bulletweight or charge.
Changing the charge to the weaker will make the left barrel shoot to the right and the right barrel to the left.As much as 10 inches changing to 232 gr
My advice: Choose your bulletweight and charge and stay there.
(It took me ½ a year to learn that)And you can shoot very precise with it
