I'm also experimenting with modifying some M&P mags and CZ mags to make use of inside the carbine. You should cut the notch within the front from the mag so it's going to lock in. I don't own any Glocks. I'd use Glock branded Journals and not the opposite copies. https://rugerp89forsale63432.bloggerchest.com/32006404/5-simple-techniques-for-ruger-shotguns