WHAT DOES RUGER P89 FOR SALE MEAN?

I'm also experimenting with modifying some M&P mags and CZ mags to utilize from the carbine. You need to Lower the notch from the entrance of the mag so it can lock in. I do not have any Glocks.I might use Glock branded magazines and not one other copies. Other folks are available which include Magpul. You could possibly try out some and find out y