I'm also experimenting with modifying some M&P mags and CZ mags to implement in the carbine. You must Lower the notch while in the front in the mag so it is going to lock in. I don't very own any Glocks. I just paid $300 to get a blue P85 https://cruzdhwji.frewwebs.com/32716373/rumored-buzz-on-ruger-p89-for-sale