We have been using the Pmag 17 GL9 in our Glock 17 for several months now. In competition and training we have put thousands of rounds through them without issue. When Magpul announced the release of the Pmag 21 GL9, we rushed to get our hands on one.

The Pmag 21 GL9 looks identical to the Pmag 17 GL9. The Pmag 21 extends from the bottom of the Glock 17 in order to make room for those four extra 9mm cartridges. The Pmag 21 also has 10, 15 and 21 round witness holes in the side.

The Pmag 21 GL9 uses the same floor plate as the Pmag 17. This includes the “dot matrix” marking area. This also means that the Pmag 21 will accept the Magpul L-Plate rubberized floor plate. If you are not forced to work within competition magazine length rules, the L-Plate is a worthy upgrade for these magazines.

We ran the Pmag 21 GL9 hard for 150 rounds to get a feel for the reliability. We did not have a single stoppage that I could attribute to the magazine. The mag-dumps were flawless. We ran 50 repetitions of “one-shot” drills to see how reliably the Pmag 21 would lock the slide back on our Glock 17. We only encountered one instance where the slide failed to lock. We could not reproduce the error.

If you have a need to gas up your Glock with 21 round magazines, the Magpul Pmag 21 GL9 is a great option. At $19.95 MSRP they are the most cost-effective method at increasing the magazine capacity of your Glock. Hopefully Magpul will have the 27 round version out soon!