Just what the title says. The only differences that I can see on their website is that the rifling on the CM9 barrel is different, and that the PM9 comes with 2 magazines rather than one. And the PM9 is $230 more expensive. I can't imagine the magazine costs that much, and I don't understand the difference between the two types of rifling well enough to know whether that justifies the cost difference. Can anyone explain it to me, or is there something I'm missing here?