The 8x56R case has more capacity than the 8x57. Not much but enough to make a difference. IMHO it works best with powders like IMR 3031 and IMR 4064. The larger the bore diameter the faster the powder needed to make it work best is a general rule of thumb but not always.
The M95 straight pull rifles as built by Steyr for Austria are tough, rugged rifles that were built for and used extensively under extremely stressful conditions. The fact that nations readily accepted them as war reparation payments says a lot about their quality. During the 1930s many of them were converted to 8x57 with a bolt head change and a magazine upgrade similar to that found on some 1888 Commission rifles that were modified to eliminate the enbloc and feed from a charger.
I reload for mine. Not as much as I used to but I use a faster powder to achieve the standard velocities that these cartridges were loaded to. They loaded a 210 grain bullet to a velocity of appx 2300fps at appx 46,000psi. Very close to any standard service charge for many other cartridges of the period.
My standard load on both Berdan primed period brass and the new Hornady Boxer primed brass is 45 grains of IMR 3031 under the .329 diameter Hornady 200 grain bullets for an average velocity of 2350 fps out of a long rifle and 2100 fps out of the carbine. It's a stout load, especially out of that carbine. It kicks like a mule but prints identical groups and has the same point of impact that period ammo shows. I tried lighter loads with slower powders but the groups on both rifles opened up more than I could live with. Both of my rifles are in excellent condition, inside and out. They shoot well if I don't flinch. Sadly these two are kind of the Rodney Dangerfields of milsurps. Most people don't have a clue how extensively they were used by the combatants of several European nations during WWI and WWII. They are well respected in Europe. I assume ammo is a bit more readily available there for these fine old girls as well. Privi makes it and it's good stuff. The biggest issue with Mannlicher style feed systems are those pesky en blocs. Especially for 100+ year old rifles. Mind you, Garands are now approaching their 80th birthdays and they use an enbloc to hold their cartridges as well. No one seems to complain until they lose them.