Coupla things... Can you get us a pic with greater detail inside the loading port, so we can see what kind of follower you have? More light, too...
Looks very similar to Chinese mags. Lots of videos on internet. Once you do it a few times, it becomes easy.
Yours is pretty cool.So, here's a few pics of one of my AK-47 drums...
Mine does NOT have a key on the back like the one in Marks' video above. Mine has a lever on the front that one uses much like an UpLULA speed loader. You can't load rounds in my drums like the video sows cuz there's no holes/slots for the rounds to go. They would fall all over the place if you tried to load the drum by taking it apart. So it seems like my drums aren't going to be of much help. But it looks like you can just follow the video Mark posted and you'll be fine.
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Also, I pulled out the 3-round follower...
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You can see the tab on the last "round" of the follower.
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This tabbed round needs to be the one that is furthest into the drum, cuz that tab is forced up against a stop by the spring when the drum is empty, which keeps the spring from completely unwinding. I suspect that you must have a similar set-up in your drum, otherwise all the spring tension is lost.
Kinda looking like a Romanian top load 75. I just had never seen one with the back off before.