One of my all-time favorite rifle cartridges!
75 grain Sierra HPs at 3300 fps or 100 grain Remington Corelokts at 3000 fps, using one of the 4350s, has been about all I've shot through it because it's all I've needed. Pressures are low and brass lasts a long time. My single brass attrition factor seems to be outright age, where some cases older than me tend to develop neck splits on loaded ammo that's sat too long.
Very accurate - three shots in a half inch when I'm "feelin' it." Not to argue for three, five or ten-shot groups - three is more than I need for hunting and if a .257" bullet doesn't hit within a half inch of where I intended, it's me, not the load or gun. Nothing against five or ten-shot groups - I'm just qualifying what I mean when I say "accurate."
The 257 is such an easy cartridge to get along with, mild report and recoil, doesn't use a lot of powder, accurate, not temperamental. The "long" action is plenty, the 98 Mauser is just about right. My brother had a Browning Lever in 257 that was a short action and I didn't like stuffing 117s and 120s that far into the case. Not sure it mattered. John Barnsness say is doesn't.
My own 'Roberts is a Coumbian FN military Mauser my dad built me many years ago. For several years, I shot it side by side with a Tang Safety M77 Ultralight with a 24" tapered octagon barrel chambered for 25 Souper and the ballistics were identical to my 22" Mauser using the same bullets, powder and nearly the same amount of powder. The Souper had to work a little harder (more pressure) to match the 'Roberts but it was still within very reasonable limits. The Souper eventually moved on but the 'Roberts will be in my estate sale if one of my daughters don't want it.
Never shot a deer with either, but quite a few woodchucks came out of their hole for the last time when a 75 grain Sierra HP caught up with them. It was definitely more decisive a result than with the 22 center-fires we used.
Sorry for the rambling babble, but any mention of the 257 Roberts pushes my "talk" button - which is also conneted to the 7x57 and 6.5x55. I'd take any of the three in a 6# rifle with a low-powered variable (and peep/post backup) and be happy. Those three are like the straight-sixes of the automotive world to me - they may not have the displacement, horsepower or RPM of a v-configuration, but they can get the job done admirably in the "low end" just the same.