with any bullet weight from 139 to 175, ( out of an older Hornady manual) try 40 grains of 3031....
its velocity will exceed that 2550 you were referring to.. and the accuracy is real good out of any 7 x 57 I've ever shot.. and others that have asked me about that load on the campfire, found out the same thing...
if you are set on going a little lighter....
44 grains of IMR 4064 or IMR 4895, with a 139 gr SP Hornady, or 140 grain Partition or Ballistic tip, exits the 22 inch barrel of my Featherweight Winchester, or my Ruger 77 Mk2...at 2800 fps....and both of those are pretty darn accurate also...
140 grain Corelokts, if you can find them, work awfully darn well also...
