Every article I have read about 8x57s Carcanos stated it could be dangerous to fire these rifles and advised against it.The Carcano rifle was designed around max pressures of 38.000psi while the 8x57 operated around 50.000psi.
When the 7.35 Carcanos were imported into USA, many years ago, there were stories circulating about these rifles blowing up particularily with reloads. The 7.35 Carcano uses a .298 diameter bullet. I can only imagine the blown up rifles were caused by the use of .308 diameter bullets in reloads.
I have encountered 8mm Carcanos at gunshows and you will see them periodically on the auction sites.