Magpul PMAG 40 Review

Whoever invented the adage, “less is more” never encountered the Magpul PMAG 40 STANAG. While it might not seem like a major achievement to younger shooters, there was a time not long ago that anything over 30 was considered too unreliable for competitive or serious use.

So how did Magpul succeed where others failed? Let’s take a closer look inside the PMAG 40 to find out.

PMAG 40 Now With 33% More Freedom!

All of the same aspects of the standard 30-round PMAG that make them so durable and reliable, are present on the PMAG 40. These magazines feature the same anti-tilt follower that prevents rounds from taking a nosedive under the chamber. This follower also ensures steady, regular feeding–regardless of how many rounds remain in the mag.

The PMAG 40 is also built from the nearly indestructible polymer as all PMAGs are, and features the same molded pattern for added durability and style points. Also present is the clip-on dust cover and polymer baseplate. The only difference here, is that the baseplate retention piece reads, “40 ROUNDS”.

The Author’s personal ‘Fighting Rifle’ LaRue Tactical complete with Magpul PMAG 40

That isn’t to say it’s not interchangeable with a 30-round version, it is. But the spring length on the PMAG 40 is much longer than the standard capacity model. Swapping springs between the two results in two unreliable PMAGS. Not to worry, it’s difficult to mix them up. With the longer spring, the 30-round PMAG is very difficult to assemble, much less reload. And if the 40 uses the shorter spring, the rounds will feel sluggish in their feeding.

But enough hypothetical failures, how does the PMAG 40 actually run?

Form, Function or Both?

In testing, I ran the Magpul PMAG 40 in three different guns. Each of them representing opposite sides of the AR spectrum.

The first was a standard M4-pattern LaRue Tactical in 5.56mm with a 14.5in barrel and permanently-attached SilencerCo ASR flash hider. The second was an SBR’d franken-AR with a PSA lower, and 8 in barrel chambered in .300blk.The last test gun is a select-fire M16A1 with a 20-inch barrel chambered in 5.56mm.

The LaRue Tactical setup ran 100% with both 55gr FMJ from Winchester and 62gr green-tip M855. The .300blk SBR also ran flawlessly with all ammunition tested. This included 110gr supersonic FMJ, 220gr subsonic FMJ and even the new Winchester 210gr solid copper hunting rounds which feature truncated hollow-points. These same rounds often cause feeding issues in aluminum USGI and even some polymer mags.

A select-fire M16A1 with a modern magazine!??! (functional) BLASPHEMY!

Lastly, I ran a full PMAG 40 through the M16A1. While the ammunition didn’t last longer than a few breaths, every single round fed and chambered flawlessly. All that remained was a smoking-hot barrel, and a thoroughly perforated paper target.

So why not replace all your PMAGS with the PMAG 40?

Size Matters

Size. The PMAG 40 is substantially longer than the original PMAGS. While this isn’t an issue for competitive shooters, it does have some drawbacks for other folks. The biggest issue, is how the extra length of the magazine prevents the shooter from firing from a prone position. The only other downside is that with the added capacity of the PMAG 40 comes additional weight – but this is obviously to be expected.

Despite being designed for 5.56mm and .223, the PMAG also feeds .300blk just fine.

Overall, the Magpul  40-round PMAG continues the company’s tradition of delivering some of the most reliable, durable magazines available. If you need a few extra rounds, count on the PMAG 40 to deliver them every time.

Jim is a freelance writer for dozens of firearm publications, the host of the YouTube channel Burst Review and the youngest author to write a cover story for Shotgun News in its 86-years of operation. Jim loves anything that goes, ‘boom’ but particularly enjoys military firearms from the Cold War and WW2. When he’s not slinging lead downrange he can be round hiking in the mountains with his wife Kim and their vicious attack dog, Peanut.

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