The 90 gr Lapua Scenar HPBT would be pretty hard to beat. I think the best results will be obtained with a slow burning powder between H-4350 and H-4831. Re-19, or Hybrid 100V would be my choice, but some guys even like Re-22. For best accuracy you will have to work up your own loads. Check with your loading manuals for the minimum suggested load and work up to the maximum load, then work away from that to find the most accurate load. These Lapua bullets shoot tiny groups from my .243 with any reasonable load and have the potential to perform well at long range.