I am also experimenting with modifying some M&P mags and CZ mags to employ while in the carbine. You have to Reduce the notch inside the front with the mag so it will lock in. I do not own any Glocks.I just compensated $300 for a blue P85 in holster worn issue and truly feel it was a good offer, even as a Ruger junkie I've a tough time viewing P se