Maxim Defense 7.62×39

Tested with EOTECH 512

Maxim Defense entered the fray just a few years back as a disruptor to the “same old, same old” firearms industry. They were initially known for their debut PDW brace and stock, a marvel of engineering. Through what we can only assume was a vision on Mescaline, Maxim managed to shorten the normal buffer system of an AR to 1/3rd the length while retaining full spring strength and buffer weight. Not just regular buffers either. They make them all the way up to H3, which is near double standard. Which would prove to be important later, like this week.

A beauty to behold

The new shorter buffer system was part of a collapsible stock system that changed the game. It made a fully operational AR system, in rifle calibers, the same length at the rear as an MP5. Which cannot be overstated as important for odd concealment situations. Like running security details, where having a visible long gun is considered uncouth. Or for those of us at home, that might want a real boy gun stashed in the truck or pantry. The Maxim stock option wasn’t cheap, but it was absolutely without peer.

Handstop included, and MLOK compatible

The next phase of Maxim’s master plan was to step up to fully in-house built PDWs, or Personal Defensive Weapons. This is a niche but important military category, that traditionally the United States has done poorly at fielding. A PDW is not meant to replace a battle rifle, as the name implies. It is meant to provide a high level of firepower in a very compact package, for limited range engagements. People usually think of this in James Bond/ Spec Ops Ninja terms, which is true. but there are other places it makes sense. Tankers, for instance. The tank is the main weapon, obviously. But you can’t send the crew members out there with nothing, for many reasons. What if one breaks down, can’t continue the advance, but also can’t be abandoned? What if a crew member needs to take a bathroom break in the woods, or stretch his legs? What if infantry support fails, and he needs to clean a knucklehead off the hatch at contact range?

In our military, you had two options. Either arm the crew with pistols, which are near useless in real combat. Trust me, a Beretta 92 with 15 rounds of 9mm on board feels pretty impotent when machine guns and artillery are in play. Or you could arm them with an M-4, which even with a 14.5-inch barrel is on the bulky side. At least inside 9 tons of steel enclosure, that was not built with crew comfort in mind. The ideal weapon would be tiny, but capable of laying down rifle like performance to 200 yards. This also eliminates pistol caliber sub machine guns as an ideal.


Maxim purpose-built a PDW for a new SOCOM solicitation meant to solve these problems. The end result was Maxim’s PDX. Maxim, more than any company I know, was born to solve the unique needs of small segments of the DOD. My first time meeting Maxim Defense at SHOT Show wasn’t my first meeting with half the staff. Maxim employs real boy ex ninjas in the R&D department, ensuring the product coming out the door isn’t some half baked Call of Duty idea. And the PDX was absolutely amazing.

Radian Raptor Charging handle and X39 BCG

This brings us to today. Originally available as only a full weapon, Maxim now sells just upper receivers from the PDX family. And this is a game-changer for AR pistols. Maxim’s PDX U.R.G upper receiver features a 5.5-inch barrel, which does wonders for overall length. Just making that short of a barrel work is an engineering feat. Making it work and stay together is borderline magic.

Maxim was also the first of the major players to bring a 7.62×39 weapon (or upper receiver in our case) to market. That was absolutely the perfect one for us to test, for a variety of reasons. 7.62×39 might not be my first choice in a 16-inch gun, but it makes a lot of sense for anything shorter. 5.56, as we have noted many times over the years, is less than ideal from shorties. 5.56 gets most of its lethality from velocity, and starts suffering badly below 14.5 inches. Get below 10.5, and in many ways, you might as well be shooting 22 Long Rifle. X39 still has enough diameter and bullet mass to be lethal at slower velocities and doesn’t seem to suffer as much loss in shorter systems anyway.

A very small package for this caliber

The other big reason for switching to 7.62×39 is ammunition costs. Even with the Biden administration price bump on steel case, it is still orders of magnitude cheaper than 5.56 or 300 AAC. Our test upper retails for right at $1200, but that pays for itself in 4 cases of 5.56 at the current price. 

The Maxim upper is perhaps best described as a terrifying piece of art. In Arid, it is stunningly beautiful, in a way many weapons today are not. The flow of the darker handguard to the lighter receiver is flawless. The extended top rail, with lower cuts to accommodate a suppressor, reflects intent in design. And the in-house designed HATEBRAKE muzzle booster does a simply amazing job of reducing recoil and flash signature. Out of a 5.5-inch barrel, 7.62×39 should be throwing a fireball like a dragon of myth. The HATEBRAKE neutralizes the flash signature like nothing I have ever seen.

Most importantly, with the supplied DuraMag special 7.62x39mm magazines, the Maxim runs. Configuring this caliber to work in a true AR platform is no small feat, many have tried and failed. The Maxim ran without a hiccup, something I would not have believed possible even a year ago.

Maxim Defense continues to innovate in a space where other fear to tread. Our 5.5 model is amazing, with the shortest overall length in class. But if 5.5 isn’t your cup of tea, they have also recently introduced 8 inch and 10.5-inch models. Maxim is rapidly becoming the name synonymous with first-rate pistols and SBR’s, and I doubt they are done surprising us yet.

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About the author: Clay Martin is a former Marine and Green Beret, retiring out of 3rd Special Forces Group. He is a multi-decade and -service sniper, as well as 3-Gun competitor and Master ranked shooter in USPSA Production. In addition to writing about guns, he is the author of “Last Son of The War God,” a novel about shooting people that deserve it. You can also follow him on twitter, @offthe_res or his website,

{ 4 comments… add one }
  • Gamebred May 20, 2022, 10:52 am

    This looks great. I’ve built a few short 7.62×39’s, and they’re great. My question on this item is the $1,200 price tag for an upper. What differentiates this upper from another 20 or 30 that are out there? There’s no doubt in my mind that this is a quality piece . . . NO DOUBT! Looks great, too! If someone handed me one, they probably wouldn’t get it back! But that’s for free. I wouldn’t pay $1,200 for it unless something REALLY made it different from everyone else.

    As one of the other posters pointed out, PSA has a KS-47 setup that uses AK mags, and they run great (my 3 do). And I use Maxim’s PDW brace on one! Love it! But the whole thing (Maxim’s brace included) is less than this upper.

    All that being said, lol, I checked and the uppers are sold out everywhere I found them, so, eh, jokes on me, I guess. 🙂

    I’d enter winning one in a raffle as many times as I could, but I just don’t see a huge advantage of the upper justifying $1,200 cost. Fortunately for Maxim, it looks like there are plenty of people who disagree. GOOD FOR MAXIM! 🙂

  • Bad Penguin May 20, 2022, 8:25 am

    AR style mags for 7.62×39 suck and are a waste of money. Palmetto and a few other companies make AR style lowers that accept AK mags but they only work with that companies upper.

  • Anna May 16, 2022, 12:57 pm

    I’m intrigued. I really love the idea of “CDWs” (civilian defense weapon). Using 762×39 is a great idea. It’s always been a better intermediate cartridge then 5.56 but we were stuck with 5.56 for AR type weapons. Using 300 Black Out was a good start, and it’s a decent round; but supply and cost have always been an issue.

    My one real wish is that it was built around a lower that used actual AK mags. AK mags ARE AVAILABLE, heck even MagPul makes good AK mags and they are readily available. The “modified” Colt style mags aren’t something you typically find on dealer shelves and when you do see them they are more expensive. For the price and availability problems the advantage of 762×39 begins to come into question. Maybe 300 Black Out isn’t so expensive after all.

  • stan May 16, 2022, 10:02 am

    I built one myself it took some time to find a barrel. I ended up with a 9.5 inch barrel . I really want to get there muzzle device. That is the one part I have not been able to fix. The fire ball. I hope it works as well as you say.

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