Different guide rod and recoil spring. Yes, the 30 Luger ammo is priced high. I have a KP89X w/ both set-up's, and an additional 30 Luger barrel and several extra guide rods and springs. I lucked out and got the last ones Ruger had. They were on their way to the dumpster from what I was told by the Tech @ Ruger, as they were cleaning out old parts at the request of someone new in charge. This was several years ago.