Excellent suggestions here regarding bore cleaning, seating depth and magnum primers. If you have trouble finding Federal 215s, CCI250s are just fine and may be just a bit "hotter" than 215s. I get excellent groups and exceed 3000 fps with H4831sc, Hunter and Magnum with the bonus that all of them are relatively insensitive to temperature changes. Seating depth is a likely culprit for your grouping issues but you might also check bullet runout. Roll a loaded cartridge on a flat surface, a mirror is ideal, and see if the bullet nose has a visible wobble.