Ocw load development help

It can be a patience game that's for sure. I'm going thru it now with a 338 Lapua. Groups with factory American eagle 250gr were terrible. 3 moa with 6 inch flyers. So far loading 250gr SMK's over retumbo it's getting better but still only 1 moa at 200 yards. I'd like to be able to smoke groundhogs at 500 or more and that's not gonna do it so I'll keep burning powder and killing paper!
 
It can be a patience game that's for sure. I'm going thru it now with a 338 Lapua. Groups with factory American eagle 250gr were terrible. 3 moa with 6 inch flyers. So far loading 250gr SMK's over retumbo it's getting better but still only 1 moa at 200 yards. I'd like to be able to smoke groundhogs at 500 or more and that's not gonna do it so I'll keep burning powder and killing paper!

those groups could be all load related , but some appear to be scope related ,parallax is out of adjustment ??
 
Do you have access to a chronograph? I find that using a chronograph for this works much better then just looking at groups. With the chrono you can see where the velocity is similar from each load.
 
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