The mechanism is very simple, as you can see from the way that Dave just dumps the cartridges into the magazine 'box'. The cover has a spring-loaded elevator built into it, and when you close it up, the elevator automatically centres itself under a cartridge and lifts it into the bolt ways for it to pick up and put into the chamber.
Take a look at the end sequence when he opens the cover, and you'll see the elevator on its articulated connecting piece.
You may have noticed a couple of what look like dings in the barrel - BUT - they aren't in the barrel!..
The outside is actually a barrel jacket, like the German G88 Commission Rifle; part of the reason/thinking at the time for doing this (as I understand it) was that the actual barrel could 'free float' within the jacket.
I hunted with a guy that used a Krag for elk.
It's an interesting historical rifle.
If my history is correct, the first thing I think of was how the Krag was out-classed by the 7x57 Mauser.
The good thing about the Krag, is that it led to the Springfield.