shoot whatever bullet that groups the best in your rifle,,after that the scope is the most important piece of long range equipment,if this is your first attempt at long range start with a scope that is mil/mil and expect to shoot it enough that you can hit an 8 inch gong ever time at the max range you plan to shoot deer,,
speed and B dont really matter if you know the come ups for the load,,5,000 fps and 2.875BC wont help if you dont have confirmed dope at the range your shooting,,
the load I am shooting now is zeroed at 100,,10 MOA gets me 500 and 29 MOA makes 1000,,but banging steel is different than hunting,,with somebody that I am familiar with is on the spotter I can get on at most any range in a couple shots and then bang it pretty good,,but making first shot cold bore hits on an 8 inch gong past 500 is beyond most weekend shooters pay scale,,
500 is about as far as I feel good about taking a shot on a live animal and I shoot a lot,,it would have to be perfect conditions for me to try it at 800,,
the best thing you could do is set up exactly where you will be hunting and make a dope chart from actual data on the scope by shooting it exactly where the deer would be standing,
dope for 800 right here may be 3-4 moa off from dope for 800 25 miles from here..
shoot a bunch and determine your max range ability,,
something else that will help you is to shoot a 22LR at 100 yards a lot and shoot a right smart at 200 with a 22LR,,it will help a BUNCH