MAGPUL – Why 40 rounds?

As you're no doubt already aware, MAGPUL is shipping a 40 round capacity PMAG. Thus far it has met with widespread approval and successful testing (that I am aware of) but I wondered since the news broke, why 40 rounds? What was the reasoning? Why not 35, or 50? Was this some sort of (righteous) marketing protest enacted in response to the shameful actions of CO State Rep. Rhonda Fields, Sen. Evie Hudak’s and their sad, ill-informed and willfully obtuse cronies in that state's Congress? I was genuinely curious.

So I asked MAGPUL's Duane Liptak, Director of Product Management and Marketing. (Note: though that sounds like an office billet, Mr. Liptak is a former shooter and instructor with extensive experience.)

“…40 rounds is a number was the number we arrived at for a few reasons,” Liptak responded. “Any longer and a double-stack mag gets unwieldy. It also becomes very difficult to make a conventional magazine carrying more weight than 40 rounds…that will be a truly durable and reliable feeding device.  So for form factor, usability, and reliability, 40 rounds is a nice package…The PMAG 40 has run through endurance tests of 8000 rounds per magazine, as well as our normal battery of drops, dust, compatibility, and abuse, so it's not a novelty item.”

As for timing, it appears to have been largely, if not entirely, coincidental. There was talk of 40-round magazine long before the latest anti-Second Amendment madness started.

“I'm not saying we'll stop there,” Liptak continues, “but in order for more than 40 rounds of capacity to work as well as we require, it would look and work a little different from the rest of our magazine line. As for timing, as you probably know, we initially announced the 40 several years back, but we couldn't make it as reliable  or as durable as we wanted to in order to meet our standards until the Gen M3 technology made it possible. So, largely, the timing of the 40 was based on the timeline of Gen M3 development. There is a certain poetic element to the release timeline given recent political events, but the timing just worked out that way.  Well…for the most part….”

If you're unfamiliar with the mechanics of the new magazine, it adds 10 rounds to the ‘standard capacity' GEN 3 PMAG, increasing overall length by just over two inches (2 1/8″). It maintains the platform compatability as the AR/M4 Gen3 and will, according to MAGPUL, feed reliably at high cyclic rates of fire (an assertion which initial tests, including Iain's look in Arizona, consistently confirm).  The 40 round PMAG will feed the HK416/IAR/M27, theM249, the MK18 and virtually any conceivable AR15/M4 variant. In the official MAPGUL video they are using M193 5.56mm NATO ammunition and a quick check through various reviews and YouTube videos available make it pretty clear the 40-rounder will reliably allow digestion of most other breeds of that caliber (as well as .223).  One thing I haven't seen anywhere is how it treats various grain Hornady TAP ammunition – once I get my hands on a 40-rounder I will advise.

Below are the compatibility demonstration video from MAGPUL and the earlier video from RECOIL Editor Iain Harrison.

Why you can trust RECOIL

---

Since our founding in 2012, RECOIL remains the premier firearms lifestyle publication for the modern shooting enthusiast. We deliver cutting-edge coverage of guns, gear, accessories and technology. We go beyond basic reviews, providing no B.S. buyer’s guides, hands-on testing and expert analysis on everything from firearms and survival equipment to watches and vehicles. 

Our reviewers are the backbone of our operation and come from diverse shooting backgrounds: Former law enforcement, military veterans, competitive shooters, seasoned hunters and plain old firearms enthusiasts. Furthermore, we’re not just gun experts, but dedicated journalists who adhere to the strictest standards of our profession. 

At RECOIL, editorial independence is the foundation of everything we publish and the cornerstone of reader trust. Our editors, writers and content creators make all editorial decisions independently, free from outside influence. That boils down to: advertisers don’t dictate our coverage, the outcomes of our reviews or what we recommend in our buyer’s guides. First and always, our commitment is to our audience—ensuring every review and article is accurate, unbiased, and driven by real-world experience. 

Whether you’re selecting your next firearm, upgrading your gear, or exploring the latest innovations in the shooting world, RECOIL provides the trusted insights you need to make informed decisions. Learn more about our Editorial Standards and how we review products.

NEXT STEP: Download Your Free Target Pack from RECOIL

For years, RECOIL magazine has treated its readers to a full-size (sometimes full color!) shooting target tucked into each big issue. Now we've compiled over 50 of our most popular targets into this one digital PDF download. From handgun drills to AR-15 practice, these 50+ targets have you covered. Print off as many as you like (ammo not included).

Get your pack of 50 Print-at-Home targets when you subscribe to the RECOIL email newsletter. We'll send you weekly updates on guns, gear, industry news, and special offers from leading manufacturers - your guide to the firearms lifestyle.

You want this. Trust Us.