I'm also experimenting with modifying some M&P mags and CZ mags to work with inside the carbine. You should cut the notch inside the front from the mag so it's going to lock in. I don't very own any Glocks. I'd use Glock branded Journals rather than the opposite copies. https://zanderorpnj.diowebhost.com/87171552/top-guidelines-of-ruger-p89-for-sale