Want a little more velocity from that 300 wby and a little larger bullet. Have you considered the 215 Hybrids? My 300 win shoots them very well and above 3000 fps. I actually gained about 50 fps with 1 gr less powder (same lot) when I swithed from a 210 vld to a 215 Hybrid. I attribute it to the shorter bearing surface. The 215's BC is very good and I have taken game within a few yards of 1300 with them.
As far as going RUM or 30-378, I have been there and I am happily back to a 300 win. So my advice is not to do it unless you are only going to shoot the 220 or 230's. The facts of diminishing returns really come into play with lighter bullets like the 210's and I don't feel it is worth the loss of barrel life. However the 230's do seem to make a more efficient chambering out of the RUM or 30-378.
As for Score High, I have worked with one of their new builds and talked with Charlie on the phone. He was helpful, honest and easy to talk to. The quality of the rifle and work was good and it shoots well.
Jeff