Around 35 years ago, I had Bevan King barrel up a pair of 9.3X57s on Turkish Mausers. I had read about the '57 in Cartridges of the World, and it appeared that it was loaded to very low pressure to accommodate the weaker 88 actions. Checked with Norma, and indeed factory ammo was only around 37,000 cup.
Having already used the 9.3X62 for a while, I was curious about the '57 if it were loaded to higher pressure. Bought the reamer, and Bevan did the job one weekend.
The Turk Mausers are very strong VZ actions, and it was no trick at all to get velocities close to factory 9.3X62 loads using Ball C2 in resized 8X57 brass. Both rifles are still bagging bears and moose.
AmmoMart had thousands of Norma 286 gr Dual Core bullets for $20 per hundred. Those bullets were accurate and deadly on big game at close to 2300 fps. Still have half a bag here.
Today, the 270 gr Speer is what I load more than anything else in my Model 46.
It is
very accurate and a hammer at 2400 fps on big game. Friend of mine calls it my 358 Winchester Magnum.
Ted