Re: Can't lower my S.D. HELP!!!
If the chrony is lying to you as others have experienced and you don't have access to another for comparison, then you might try (a) shoot another rifle and good load to see how that chrony's, (b) go ahead and try your 300wm at long range. If it groups well, then perhaps the chrony is still suspect. If it strings somewhat vertically, then it may be telling the truth.
In any case, you'll save money with Lapua brass. ...easier/better prep/quality/concentricity, fewer shots wasted, and more reloadings.