My M77MkII and recently-manufactured #1A both have shorter throats than either my pre-warning M77R or my M77ST. Maximum loads are definitely NOT interchangeable! The R can handle the most powder of them all, but shoot one of those in the MkII and it gets all kinds of unhappy.
Mule Deer once wrote in an article that H4350 is a good all-around powder in the 7x57, but H4831 shows an advantage with bullets of 160 grains and heavier. My experience mirrors that, but I tend to simplify things and stick with H4350 in all the weights I shoot, from 145 through 175 grains. My loads are plenty accurate, and the deer in the freezer don't mind.
I suggest the following loads in Ruger rifles chambered for 7x57, working up carefully, of course:
145gr Speer Hot Cor, 49gr H4350
160gr Speer Hot Cor, 46gr H4350
175gr Hornady spire point interlock, 45gr H4350
If you can't kill deer with those, it ain't the gun's or load's fault.
