I just bought a new Kimber Classic Stainless and it's my first 1911. I've put about 350 rounds through it and I'm having the slide lock back with rounds still in the mag. I have 4 mags, the original Kimber, 2 McCormick 8 rounders, and 1 Wilson 8 rounder. The problem only happens with the Wilson mag. I'm absolutely positive that I'm not lifiting the slide lever up with my finger. Any ideas on what the problem is? Thanks.