Ah, I can help you. I have been working on 8 x 57 loads, with this bullet (and others), for months now. First of all, Jim Watson is correct, the bullet was designed for the 8mm Magnum. However, there are good loads to be had (in 8 x 57). The other thing to understand is that, for hunting purposes, you MUST drive this bullet to a minimum of about 2400 fps (at the muzzle), in order for it to expand reliably. This info I have from Remington, directly. That is the design velocity. So, keep that in mind when developing hunting loads, with this bullet. For target shooting, of course, it does not matter.
First, IMR-4064. The most accurate load in my M48, with the 185 PSP bullet, is 42.0 grains, in Rem. cases, with Win. LR primers. This is about a 2150 fps load, thus too slow for hunting. The max. charge, with this bullet, is about 48 grains, or so. My M48 does not seem to like max. loads, so I am not usuing the 185 grain bullet for hunting. 42.0 grains is quite safe, so you might start there, and work up.
Next, Alliant Reloder 15. This is a nice powder, a bit slower than the IMR-4064....so more of a "push", rather than a sharp recoil. This powder also produced good accuracy in my M48. About 41 - 42 grains produced the best groups. Oddly enough, I also got good groups with 48.0 grains, which is certainly fast enough for hunting, with this bullet. 42 grains is likely 2100 - 2200 fps (though this is a guess). A max. charge would be about 49.0 grains, or so. Again, my rifle likes mild loads best. I would suggest starting at 41 grains....and working up.
Then, IMR-4895. I have just started using this powder, so I do not yet have any definitive accuracy numbers. However, from my testing so far, about 42 grains produces the best groups, with this bullet (in my rifle - which seems to be stuck in a mild-charge "rut"). A max. charge is about 51 grains. I have been in contact with someone who is also testing this powder and bullet....and he has successfully taken deer with this bullet, over 48.5 grains of the IMR-4895. This load chronos at about 2550 fps (his chronograph). This is certainly a good hunting load, just about ideal with this bullet ....and he likes it very much.
Finally, I will pass on a funny result. I have been reforming .30/06 brass, to 8 x 57 dimensions, as it is cheaper than 8mm cases....and produces a thicker case, with better bullet tension. In most cases, I am crimping my 8 x 57 loads, because the regular 8 x 57 brass has insufficient tension, from my sizing die. Anyway, I loaded 50 reformed cases with a light charge, 33 grains of the Alliant Reloder 15..and the Rem. 185 PSP bullet....for fireforming purposes. I chose the 33 grain load simply because it is about 65 % of cases capacity, so it would be safe, but a minimal charge. I used the bullets simply for the heck of it, because I had lots of them. Funnily enough, this load consistently groups at less than 1"....at 50 yards. The most accurate load of all, in my finicky M48. And with cases that didn't even fit the chamber, to boot. Go figure......
Well, that's the extent of my experimentation with this cartridge, so far. I hope that this information will help you. I am still experimenting. I have also just acquired a very nice M48a....and I'm restoring it now. I'm looking forward to trying it...and seeing what it does (and how it compares to my M48). Anyway, good luck and let us know how the load testing goes.