The correct designation is 6.5x52
. 6.5x55 is the cartridge used in Swedish Mauser rifles and is not compatible.
The "CAL 6,5" marking indicates that the rifle is chambered in 6.5x52. The other WWII Italian cartridge was the 7.35x51, and these rifles carry a chamber marking of "CAL 7,35".
I do not own a Carcano, but IIRC you must use the proper en bloc clip to fire the rifle as a repeater; it will only work as a single-shot without a clip in the magazine. That said, Carcano clips are readily available on the 'Net, and even at some well-stocked local shops that specialize in military surplus.
That rifle appears to have an M1 Carbine front barrel band grafted onto it!
I've seen some interesting garage workshop projects on old milsurp rifles, but that's something I've never seen!
[EDIT] It appears that BillM types faster than me.