Good test, but I wuld say your results are inconclusive. From what I've read here, Bergers like to be seeated to the lands or slightly jammed or slightly off. So I would recommend trying some seated to the lands. Also, you just might not be hitting your rifle's sweet spot for this bullet and powder combo. It's the old which came first, the chicken or the egg?
I'm going to be doing some load development on the Bergers and my approach will be to seat them to the lands based on what I've read and find the best powder charge for accuracy starting with max and working down. Then I'll try fooling with the depth.
Hope you get it worked out... those groups are plenty good for 400 yd shots
You might also try anther powder and/or bullet....
one more thing.... I found loading 210 Bergers to the lands in my Sako 300 WSM
gave them only 2/3rds contact with the neck. I dont think I could have loaded the 190's to the lands with much contact at all.