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This results in an Ogive for the VLD at 2.729
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If the measurement from the case head to the ogive, when the projectile is seated touching the lands is 2.729, seat the projectile deeper.
I'd suggest loading up ogive lengths in the following:
2.719" (or .01" gap between ogive and rifling)
2.714" (or .015" gap between ogive and rifling)
2.709" (or .02" gap between ogive and rifling)
2.704" (or .025" gap between ogive and rifling)
2.669" (or .03" gap between ogive and rifling)
Once you determine what the jump into the lands needs to be to eliminate the overpressure issues, you can start making .002" or .001" or so adjustments up and down to fine tune the accuracy.
I don't seat that far off the lands, but it sounds like in a magnum type design like the .300 WM, you want a little more room between the lands and the ogive to alleviate pressure spikes.
You have to understand that each and every rifle and round is completely unique. Because I may find the best accuracy out of my .243 with a projectile sitting .003" off the lands does not mean the next guy will. He may need a greater jump, or may need to seat touching or even into the lands. You need to understand when a rifle doesn't like something, and discontinue doing that action. Continuing to shoot when you are popping primers and seeing extractor marks is a bad, bad, bad habit to get into. Simply because a book says X does not mean that it is 100% applicable across the spectrum of rifles in that caliber - and in this case, it is certainly not applicable to your rifle.
Your gunsmith would be a great source to help you out if you are continuing to have issues. I'm kind of surprised he didn't develop a load for your gun after putting the barrel on to be honest.