Re: Reloading data for the 7x57 mauser
H4350 gives good results in the caliber (though can't comment on accuracy, for the reason stated below). I can go as high as 48 g. with a 140 g hornady spirepoint in my Ruger 7x57 without pressure signs (remington brass). Look on the hodgdon webpage for some 7x57 data. Most of the 7x57 data you will find will be weak because of the existence of the M96 mauser, which supposedly has less action strength than the M98. I have also used H4895 and IMR 3031 for lighter loadings in this caliber. H4350 or H414 have produced best velocity, though.
FWIW, my ruger doesn't shoot worth a sh**. I've spent more time trying to make it shoot than any other rifle I own. So ... I've got plenty of time reloading for the caliber, but can't tell you much about what works accuracy-wise. I've given up on the damn thing, its more fun to make ragged holes with my .308's.