I built a 6.5-284 last year and it has been the easiest rifle that I have ever loaded for.
Optimal velocity is 2950 +or- a few.
I have had very good succuess with sierra 142s and Berger 140.
4350 should be getting you where you want to be. I personally shoot standard H4831..
My gun and a 28.5" barrel and my velocities are 2950 with 50.5 grains of powder.
The biggest thing that I have learned is that your seating depth plays a huge role with VLD bullets.
My gun shoots .1 to .3 inch groups and 100 but wouldn't group well past that with the Bergers.
I was jammed into the lands, but when I back off a little my groups went from 1.5-2" at 100 to .4"
If your 4350 is showing promise with low spreads over the graph try playing with seating depths a little. Start into the lands and back off from there..
Here is a little info from the Berger website:
For years we have relayed that it is best to jam the VLD into the lands for best performance. This works for many rifles however there are many rifles that do not shoot the VLD well when the bullet is jammed. We have learned that the VLD can shoot best as much as .150 jump off the rifling. VLD bullets can be sensitive to seating depth and it has been found that these bullets shoot best in a COAL “sweet spot”. This sweet spot is a COAL range that is usually .030 to .040 wide.
The quickest way to find this sweet spot is to load ammo at four different COAL. Start with a COAL that allows the bullet to touch the rifling. The next COAL needs to be .040 off the lands. The third COAL needs to be .080 off the lands. The last COAL needs to be .120 off the lands. One of these COAL will outperform the other three by a considerable margin. It has been reported that the VLD bullets don’t group as well at 100 yards but get better as the bullet “goes to sleep” at further ranges. We have learned that by doing the four COAL test you will find a COAL where the VLD bullets will group well at 100 yards. Once the COAL that shoots best is established you can tweak +/- .005 or .010 to increase precision or you can adjust powder charges and other load variables. Frankly, those who do the four COAL test usually are happy with the results they get from this test alone.
This is a typical group from my gun at 100 with 50.5 grs of 4831..This is a 6 shot group with a called flyer in the bottom left.