I'm also experimenting with modifying some M&P mags and CZ mags to use while in the carbine. You have to Reduce the notch inside the front from the mag so it's going to lock in. I don't own any Glocks. I just compensated $300 for just a blue P85 in https://zionnqolk.blogunteer.com/31295043/rumored-buzz-on-ruger-p89-for-sale