I would worry less about trajectory and more about accuracy at those distances. If you get any kind of accuracy out of a 250 grn bullet and 150 grns of powder I will be surprised.

I had to go with a heavier longer bullet with a better BC to get the accuracy I wanted at those distances. I suggest looking at the Precision Rifle bullets if you want that kind of range. And pellets probably won't cut it. Loose powder will let you work up a much better load for accuracy. Faster is not always more accurate.

Paul