Gun shops often get it wrong

[Jack]

I too doubt an 8x57 cartridge would fit a 7.65x53 chamber, but, better safe than sorry.
I've run across a number of similar errors over the years. 98's marked as 93's, etc.
The most interesting one was a long time back, when a whole rack of M-1 carbines was at a large gun shop that had a nice range and would let you try before you buy. I perused the rack of carbines and picked one up that looked just a hair different. When I asked if I could try it, they handed me a 30 round magazine, loaded, and sent me to the range, where, I pointed down range, loaded up, and proceeded to dump 30 rounds into the backstop in one burst. The gun was an M-2.