In the photo, Leopold and Niedner are wearing Mills belts. Were they carrying fixed ammunition directly in the belt loops? Or were the cartridges carried in tubes? The base band bullets seated in the mouth of the case would have been rather fragile.

If you ever disassembled any pre-WW2 Italian ammunition for the Carcano rifle, do you remember the inside of the case mouths? Pretty close to a base band bullet design.