DESCRIPTION:
First an FBI report concerning the ammo:
http://jfk.hood.edu/Collection/Weisberg%20Subject%20Index%20Files/F%20Disk/FBI/FBI%20CIA%20Relations/Item%2006.pdf

The reference I found quoted: “..traced back to the WESTERN CARTRIDGE Company of Chicago. They were from a batch of 400,000 ordered by the USMC. The ammunition was manufactured in 1954 (not 1958 -some reports give this later date). The FBI report in which this information appeared specifies that [paraphrased] ...since the Marine Corps has no weapons in which 6.5mm Mannlicher-Carcano ammunition could be employed...the ammunition was purchased (presumably for the CIA) by the Marine Corps for reasons of cover…" Also, the .38 bullets said to have been found in Oswald's pockets had black leather marks on them that indicated they had not been taken right out of the box, but had been in a black leather holster for some time.

As to the two guns thy are a Carcano M91/38 bolt-action carbine with a 4x power telescopic sight from an advert placed in American Rifleman magazine by Klein’s Sporting Goods (see image #1). He used the false name of Alek Hidell and a 38 calibre Smith & Wesson ‘Victory' Model 10 snub-nosed revolver in January 1963, paying $29.95 plus postage