As of this writing, Magpul currently manufactures and sells two generations of the Magpul PMAG magazines for .223/5.56x45 rounds. These magazines are labeled Gen M2 MOE and Gen M3. The differences in the two generations are as follows:
1. Dust Cover – This is one of the biggest differences between the two generations. The Gen M2 does not ship with an impact/dust cover anymore. Dust covers are shipped with all Gen M3 models. This allows shooters to keep debris out of their loaded or unloaded magazines. It also protects the feed lips from impacts while bouncing around your storage box. Dust covers are a personal preference and a debate for another time. Note: Magpul PMAG Gen M3 dust covers do not fit PMAG Gen M2 magazines.
2. Floorplate – The butt plate on the Gen M3 is slimmer than the Gen M2. This makes it easier to fit into tight mag pouches.
3. Platforms – In addition to all AR-15 rifles that the Gen M2 operate on, the Gen M3 operates on non-Colt-spec platforms such as SCAR MK 16/16S, HK 416, HK MR556A1, M27 IAR, British SA-80, and others as well.
4. Over-insertion Stop – The Gen M3 has an over-insertion stop on the spine of the magazine. This allows for more aggressive magazine changes with no danger of malfunctions or over-insertion.
5. Dot Matrix – The Gen M3 has a paint pen dot matrix located toward the bottom on the side of the magazine so that one can mark up their magazines i.e. MAG1, MAG2… DAVE…. 300 (for 300 blackout).
Some of the other differences mentioned by Magpul are that the Gen M3 has improved overall strength, a new low-friction, four-way anti-tilt follower. The color of the follower in the Gen M3 is grey to differentiate it from the Gen M2 follower which is brownish in color.
Whichever PMAG you buy, you will be guaranteed a premium, well-built magazine made in the U.S.A.