Two law enforcement officers stated they witnessed a Mauser and one stated he witnessed a stamp. That's a positive identification of a weapon. Two men said they saw the same weapon.
Weitzman stated it "appeared to be a Mauser". Not exactly an overwhelming identification. Maybe had never seen a carcano and had no idea what a carcano looked like.
Boone, who found the rifle, stated he watched Fritz come and pick up the rifle and eject the cartridge which is known to be a carcano cartridge--- CE 141. Boone then watched Day come immediately, take the rifle from Fritz and photographed the rifle, which is known to be part of the evidence collected. What Fritz handled and Day photographed in front of Boone was a 6.5 carcano.
Craig's only statement was supposedly about having seen the "mauser stamp" on the barrel. There is no such thing and also seems very similar to all his other fairy tale encounters that day.
If you have real witnesses who positively identify the rifle as a Mauser and the actual model of the Mauser that would be helpful. There are lots of Mauser models and calibers built for many different countries. Claiming it was either a Mauser or 7.65 Mauser is an extremely large and very broad and diverse description.