RE: Which bullet for the 8mm Mauser?
I got a new Remington Classic in November in 8x57mm Mauser. I've started working up a load for it, and have tried the Hornady 150 grain Spire Point with IMR 3031 powder, and the Remington 185 grain PSP bullet with IMR 4064 powder. I will be trying other powders with both bullets, but have found that 46.5 grains of IMR 4064 over the Remington 185gr yielded average 3 shot 100 yard groups of 0.75" (biggest 1.38", smallest 0.38".) I found that 48 grains of IMR 3031 over the 150 grain Hornadys yielded 5 shot 100 yard groups averaging 1.19". I have some Hornady 150s loaded over various weigts of IMR 4064 but have not yet had a chance to try them.
My experience with reloading 8x57 is limited, but extensive tests with .30-06, 6.5x55 and .243 all suggest that IMR 4064 is a very satisfactory powder in terms of accuracy. I have not been impressed with IMR 3031 or IMR 4831 in terms of accuracy in any of my rifles. Other posts on this forum come from guys who have enjoyed excellent results with these powders, so you need to see which works best for you in your rifles.
Good luck!