Re: 280 out to 1000
Sierra 175gr HPBT Matchking, any MV above 2450fps gets you to 1000yd at about 1300fps or better. Hodgdon H1000 published loads, min 54.0gr yields about 2500fps, max 57.0gr (compressed) yields about 2580fps. Find an accuracy node somewhere between those two limits with ladder testing. For hunting, the 175gr SBT Gameking has a lower BC, but is highly adequate within 800yd, and maybe further.
Greg