Would it require a complete disassembly as depicted in that picture or just connecting the barrel to the rifle stock? This is not a trick question as I have never assembled a MC rifle and am curious as to the answer. It has implications for the minimum amount of time it would have taken for Oswald to assemble the rifle.
OK Rich.... actually I have only disassembled my shotgun [Winchester 1400 12 ga. auto]
It isn't hard to do but I have Teflon screwdrivers so I don't bugger the metal.
But shotguns are different from rifles.
I have a .22 Marlin semi auto.. the trigger housing is screwed into the stock.
Have you seen the link here?
http://dealeyplazauk.org.uk/pdfArticles/TheMannlicher-Carcano.pdf It should have been determined and reported by the FBI [Robt Frazier?] that the MC in question was indeed reassembled like quickly with a what? Crude fastening device? I mean they analyzed Oswald's pubic hairs and stuff like that

I see you found a link.
http://thisoldrifle.com/carcano9138/rifledisassembly/index.asp