hrmmmm. It seems like you got some bad mags if they are jamming up. I've shot a couple hundred through with a 30 round mag, no jam ups.
Ok, let me clarify. It jams in two situations. First, when the magazine is near empty (maybe ten rounds left), the spring loses its force, and rounds can jam in the breech. The 30 round mags may not suffer the same fate because they have 20 fewer rounds so the spring isn't stretched out as far. Second, if you use some of the high velocity rounds like Remington Yellowjackets (think that's the name) which have a conical nose instead of a round one, the rounds can again jam in the breech.
I also hate shredding my finger trying to get the last ten or so rounds in. Damn thing is tough!