I've already loading this to 60 rounds before. Contrary to what you might read, the physical effort needed actually isn't that hard.
But I unloaded it recently and then went to load the rounds back in, and now it stops at 48 rounds.
Before everyone tells me to just put some elbow grease into the lever, the lever isn't the problem. The problem is that the top round doesn't compress far enough to make room for another round regardless of how many times I ratchet the lever. It's not hard to push the lever all the way, but the 48th round at the top doesn't actually move down when I do it. It feels like pressing down on the 30th round of a normal 30-rnd pmag, there's a sudden hard stop.
If it weren't for the fact that the round doesn't actually feel that hard to press down on before suddenly meeting a hard stop, or for the fact that I've loaded it to a full 60 rounds without much effort before, I'd be inclined to tell myself that I just have baby hands and need to put some elbow grease into it.
But the abrupt change from not-hard-at-all for the 48th round to full-stop when trying to do 49 makes it seem to me like there's something getting caught on something else inside the drum.
Or if you don't know what's wrong, feel free to chime in with baby hands jokes
Update:
Figured out how to fix the problem. Description in the third reply of the thread.