Hi Mark! and hi to all, I guess we missed the most basic instruction..
. the toggle assembly MUST ALWAYS!!! be locked open, to insert the drum... There is NO WAY you can compress the rounds once you've turned the corner on the mag to the main spring, probably 13 plus rounds... Load it up again, and try with the bolt toggle locked open and you will be surprised...
... still more to learn, best to you, til...lat'r...GT....
BTW, you should NOT be loading full 8 round luger mags with the toggle down anyway... it will do it, but it's really hard on original magazines?... not to mention grips and such....