Hello Dennis, and welcome to LRH. I am an avid 300 win shooter. I have put together many 300 wins for hunting to 1000 yards. I would recommend H-1000 for powder and FED GM 215M primers. Since you are going out that far I would be looking strongly at bullets with a high BC to fight drift. My choice would be the 210 Berger VLD or the 215 Berger Target Hybrid. I have had great luck with both hunting with my rifles, most recently the 215's. The 215's are easy to work up a load for,and their BC is at the top of any production bullet for the 300 available today. I have taken a few antelope past 1000 yards and as far as 1285 and they still expanded very well. A starting charge for the 215 and H-1000 would be 72 gr and work up.
This thread may interest you. In it you will find actual field photos and data from many big game kills with the 215 Berger. After reading it you may have an idea if this is the kind of performance you desire.
Hope this helps.
Oh, for a tip: Practice ,practice ,practice!!