I had the same problem with the Hi-cap .40 mags. I could only get about 7 rounds in before it became dangerous...literally creasing cases. This type of spring tension is great for reducing FTL, but a real pain in the loading department. I got the HKS 942 at Sportsman's Warehouse for $7.99. My mags fit just right, and it only takes seconds to load all three mags supplied. At the range, my friends firing Baby Eagles in .40 were also able to use this loader. Someone with an SC would probably be better off with the Super Thumb offered by PistolGear, since the finger extension mags don't fit in the HKS.
This HKS job does feel somewhat flimsy, but it does the trick. The price is right.
If one of you machinists out there figure a way to "copy" this loader in aluminum or high-density plastic, you may be on your way to some real $$$.
I'm somewhat concerned that many of you, here and in other topical posts, reported that the mags get easier to load. This would indicate that the springs may not retain the tension necessary to reliably feed ammo to the chamber. Here in the desert, where dust and sand are a constant, high spring tension is a good thing.....