8x57, I ussually load 47.5gr of 4320. But w/ some rifles I have backed down to 42 grains or up to 49 in others. These are for a 175gr bullet. I load 37 grains for 170gr GC lead. Don't pass 47 in most rifles, even a M98.Jp
I use 42 gr. IMR 4064 with Hornaday 150 gr. jacketed bullets. Moderate load that is pleasant to shoot and one which I do not worry about cracking a stock. I have used up to 45 grains, but have not seen any increase in accuracy, just in the boom.
When shooting cast bullets, theyare 180 gr. gas-check bullets sized to .002" over bore size, with 25 gr. AA 5744. This is almost down to gallery load, but is extremely pleasant to shoot, fairly accurate, and easy on the pocketbook. Don't use this load with jacketed bullets as at 1,550 to 1,600 fps you may be getting down to where you could stick a bullet in the bore.
I cast my own 8mm bullets from the Lyman 160 graing Lovern style bullet. I use either 4198 or 4895 imr powder at 1,900 fps. Gas checked. Very accurate and mile recoil. Very cheap to shoot. I make my brass out of 30-06 cases.
I like either 42 gr of 4895 or 44 gr of 4064 and a 150 gr bullet. Neither are too hot, but I'd load down further for an 88. I've also tried both with 170 gr and 185 gr bullets with no issue, but I'd say that it is getting on the warm side for the 185. Not hot-yet- but getting there.
For cast lead, 18 gr of SR 4759 or 2400. They also do passably with jacketed if you want a really mild load.
An important question before you reload. What diameter is the bore? The generic term 8mm (8x57) is not sufficient to create safe and accurate loads. 8mm in its various forms can require a bullet from .310 to .323 depending on the bore. Of course the load data will chage with the type of bullet.