Marsh,
I don't know this, since I have no large molds in Aluminum, but I think it may be a large mold/small mold issue. I have a 200gr .44 mold from Lee for my 44-40 that works fine, too, and I like the double mold idea. Of course, I'm not nearly as picky with my 44-40 and RB bullets as I am with my .40 and .45 Rifle bullets. Don't even bother to weigh the small ones. I can't really judge them on the sam basis as I use for the big ones. If I did, maybe I'd have the same problems.