I bought a bunch of new clips a while back. same issue. The solution was two fold. To make the rounds slide better (especially the top round of a fully loaded clip), a nice, long tumble in walnut media did the trick. To make cartridges easier to load, apply some light flexing. I made a wood block of just the correct size to insert one way then twist it with a pair of pliers so the other dimension will gently spread the clip. A couple dozen twists of the block improved the situation greatly.