Re: Very High ES?
After confirming that your chronograph was yielding valid velocity, I would try alternative powder charges first. Bullet seating depths second. Then switching to different brands of primers third.
With any specific bullet, I have found the powder, and then the charge weight of the powder to typically have the greatest affect on ES and SD. Typically... not always.
Berger VLDs are often seated into the lands ~0.010", and sometimes into the lands versus off the lands can have a substantial difference on both group size and ES. Reduce your powder charge a couple grains before jamming them into the lands and then work back up looking for the sweet spot(s). Jamming them into the lands will spike the pressures compared to seated off the lands. Thus the need to initially back off the powder charge prior to jamming them.