Re: estimate on 2 guns
Assuming Ninja007 is in the U.S., the story seems, at best, unlikely. With some exceptions, the only soldiers who carried Carcanos in WWII were Italian, and I agree with others that those brought here as POWs or who immigrated later didn't bring their rifles along.
Actually, very few American units encountered Italian troops and few Italian weapons were brought back (compared to the tons of German weapons). Most of the Carcanos in the U.S. were imported by the shipload after WWII by outfits like Interarms. (One of those imported Carcanos played a role in the tragedy in Dallas in November, 1963.)
The 6.5 caliber was not "new" at the start of WWII. It was the old caliber, adopted with the first Mannlicher-Carcano rifle in 1891. By the WWII era, the Italians (like the Japanese) had found the 6.5 inadequate and decided to increase the bullet diameter and weight, hence the 7.35mm. As war loomed, the Italian military had second thoughts and converted most of the 7.35 caliber rifles and carbines back to 6.5 to simplify ammunition supply. The only ones not converted were those that were already out of the country.