Right after World WAr II there was a home industry involved with rechambering 6.5 Arisaka rifles brought home from the South Pacific to a wildcat called variously the 6.5X.257 or the 6.5 Spence Special. This was simply the original chamber reamed out to accept .257 Roberts brass, reinventing, for all practical purposes, the 6.5X57, which had been around much longer.

I always thought this was a perfect cartridge for the Mauser 98 action for use on whitetail deer. Its competitor, the 6.5X.308 (.260 Remington) is better suited for a true short action, but is harder to make feed correctly in a Mauser action.

Unlike the 6.5X55, 6.5X57 brass can be easily made from a number of other sources, such as the 6mm Remington, the .257 Roberts, the 7X57, and even the 8X57 and the .30-'06, if the reaming or neck turning required is not a problem.

I have one of both, a 6.5X.257 on a Mexican Mauser small ring action and a 6.5X57 on a BRNO 22F. I'm sorry not to be able to quote loads and velocities, but my chronograph has been out of action for some time now, and I don't have access to my old records. I think of it as a bit longer ranged (flat shooting)than the 6.5X54 Mannlicher Schoenauer, without the accompanying noise of the even larger 6.5X.284 or 6.5-'06. With fast burning powders and relatively heavy bullets the short barrel of the BRNO carbine is not an ear splitter.