SIG MMG 338 Program Series

Magpul – PMAG 30 AR 300 B GEN M3 for .300 Blackout

Why a Dedicated 300 BLK Mag?

While some .300 Blackout® ammo runs consistently in 5.56 magazines for some users, others have found it to be problematic. At the request of some demanding professional users, we have designed an ultra-reliable magazine dedicated to handling the challenges of various 300 BLK ammunition types.


Optimizes Round Stack

300 BLK rounds come in a variety of shapes and sizes, and some don’t interface correctly with the contact areas in a 5.56 mag. This can ultimately cause stoppages. By designing a PMAG specifically for .300 Blackout, we were able to optimize the round stack for the increasing variety of 300 BLK projectiles.


Minimizes Side Pressure and Friction

Dust or suppressor fouling magnify the problem—especially with certain subsonic rounds. This creates side pressure within the mag, adding friction and slowing the stack movement upwards. This is a geometry issue that our PMAG 30 AR 300 B is engineered to solve.


Avoids Caliber Misidentification

The dedicated PMAG for 300 BLK includes tactile and visual cues that differentiate it from 5.56 PMAGs for those who need to switch types of ammunition rapidly. This helps to avoid dangerous misidentifications and cross loading.


Maintains PMAG Reliability

Like all PMAGs, the PMAG 30 AR 300 B GEN M3 magazine features a long-life USGI-spec stainless steel spring, four-way anti-tilt follower and constant-curve internal geometry for reliable feeding.


6 Responses to “Magpul – PMAG 30 AR 300 B GEN M3 for .300 Blackout”

  1. Dualstrike00 says:

    Now here the million dollar question “does it work for the 5.56 with the new changes”?

    • SPQR476 says:

      It will feed 5.56. It actually feeds it pretty well, but we didn’t go to anything over a compatibility firing schedule to confirm, as we know that it won’t be as reliable as a regular 5.56 GEN M3 for the same reasons that a regular 5.56 mag isn’t as reliable with 300BLK. But, in extremis, you can feed 5.56 from it.

  2. tirod says:

    Point being that the .300 BO needs more room near the ribs forward of the cannelure. The stack is wider at that point than 5.56, just the same as 6.8 was too big (all over) to work in a 5.56 mag, either.

    Reducing the rib intrusion makes more room and the round then feed upward more readily. This is why on vendor was literally machining Lancer mags to remove the rib for an alternative caliber.

    Mags are made to fit a particular size and shape cartridge, no, you really can’t just stuff whatever you like into one and then get it to function correctly. In fact, if the mag doesn’t feed right you are left with a system which jams – it’s the reason that the AK47 worked so well despite it’s second rate piston system and manufacture. The mag was optimized for extreme hard use and Kalashikov accepted no compromise whatsoever.

    Contrast that to the concept the original AR10 mag was disposable after one use and we are now going back full circle. It’s the mag doing all the work and anything that detracts from it’s function is accepting a failure point.

    I don’t see Magpul accepting failure here. They are fixing it.

  3. snakeman48 says:

    Here’s hoping they make them in a 20rd version as well.

  4. Monty says:

    The visual and tactIle cues really appeal to me because I am always concerned about safety. I would buy plenty of these if they came in 20 round configuration. Subsonic bullets are heavy an 20 rounders work well from prone and from rests.