There is no hard and fast rule regarding bullet jump or having the bullet engage the rifling. You have a starting point that is all. If you are using the magazine often times that will restrict seating the bullet out of the case and closer to the rifling.
Berger suggests trying four seating depths which are quite far apart. "Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don't give up first. (their opinion not mine) Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.
Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:
1. .010 into (touching) the lands (jam) 6 rounds
2. .040 off the lands (jump) 6 rounds
3. .080 off the lands (jump) 6 rounds
4. .120 off the lands (jump) 6 rounds
Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:
1. .010 off the lands (jump) 6 rounds
2. .050 off the lands (jump) 6 rounds
3. .090 off the lands (jump) 6 rounds
4. .130 off the lands (jump) 6 rounds
Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL +/- .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards). "
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I have had good results by seating the bullet closer to rifling I have done so in small increments to see if there is a trend. If possible I like to move in .005" increments.
If you already have the bullet seated out as far as possible and still fit and feed from a magazine then go the other way. Seat the bullet deeper into the case in .005" increments and note changes. Often a tighter group can be obtained.
For grins I seated a 308 with 168 sierra matchkings progressively deeper in .002" increments and went past the tightest group. As the bullet was seated deeper the group size opened up then with even more seating it began to tighten up again! Of course you can only go so far in seating deeper into the case but that test proved to me that there can be more than one sweet spot of tightest group size. See pic. Numbers represent setting numbers on my comp die.
I have used Berger VLDs in a 257 Weatherby and a 7mm RUM with jumps in the .70-200" range with good results. There was no way I could have gotten the bullets any closer to the rifling in these hunting rifles.
There is an issue in trying a variety of seating depths, repeatability. If you don't have a competition seating die it is going to be difficult but not impossible. You will need a comparator like the one linked to precisely measure ogive to base distance.
Hornady LNL Comparator Body w/ 14 Inserts - Sinclair Intl
You will also need to make a dummy round for every seating depth so you can measure from it later to set up the seating die. I have done it both ways and the competition seating die is the way to go IF you intend to keep that chambering. (I often help friends with their loads and no special seating die is available.
Good luck on finding better groups. Come back and report on your results. Ask more questions, many here are willing to help.
