Piston PSA KS47 – Chapter 1: Unecessary Exposition

Chapter 1: Unnecessary Exposition (None of this is really important. If you don’t care, please skip to Chapter 2: The Build)

There are many people in this world that cannot understand the pure, unfathomable lust mankind has for experimentation and learning. When confronted with new ideas, they say things like, “You can’t go that far with a ship, you’ll fall of the edge of the earth!” Or, “Why bother finding a cure for disease? People are going to die anyway!” Well, I don’t care to be inundated with their monotonous ‘facts’. It’s not their approval I seek, for I posses an unfathomable itch… An idea… nay, a vision. I foresee a conceptual animal born of two different species… a  true abomination… Can I force together two different worlds and make a gun so hideous, so vulgar, and so illogical that it defies logic to pursue?

The answer is, quite frankly, yes.

What exactly am I talking about, here? Well, I want to build a true hybrid firearm… Or better yet, I want to build an AR that identifies as an AK. For all intents and purposes, it will still be an AR, but with important differences in its physiology. It will piston driven, chambered in 7.62x39mm, and fed from AK-47 magazines; a feeding method so native and natural to the cartridge that it will be like feeding from the teat of Mother Russia herself.

I will not claim to be the first to do this, but I will say that at the time of writing this article, I’d yet to find an example of such a beast. All AK-mag-fed ARs I’ve found appear to be direct impingement… and I’ll have none of that.

You might ask why I don’t just get an AK. Well, I don’t want a whole AK, I just want the magazine. Don’t get me wrong. AKs are very simple and reliable firearms. The gun, by design, was meant to be reliable and robust (to an extent). But, one of the biggest sources of the AKs reliability is the magazine specifically designed for the 7.62x39mm cartridge. The continuous curvature of the magazine addresses the aggressive taper of the cartridge, allowing for the smooth travel of the follower and prevents cartridge tilting.


What? I didn’t answer the question? Well, I’d prefer to have an AR platform because they are inherently more ergonomic and accurate than AKs. Says whom? Will you please stop asking questions?! AKs can be accurate, but their design includes features that are not necessarily conducive to accuracy. First, the handguards are often clamped to the barrel, which means any forces imparted onto the handguards are also imparted onto the barrel. For example, resting the handguards upon a surface for stability can impart flex ever so subtly onto the barrel, leading to shot inconsistency (yeah, I know it’s minuscule, but it’s an excuse). Second, the piston axis sits very high above the bore axis, causing the piston to impart considerable leverage onto the barrel during cycling, amplifying barrel whip.


ARs, conversely, have greater aftermarket support and countless free float handguards available, which do not even touch the barrel. In addition, the piston axis on the AR sits lower above the bore, imparting less leverage than the AK (leading to less barrel whip).

Barrel whip? Where is the science to back this up? GUHHHH. It’s basic physics involving mechanical advantage. The gas block acts like a lever, the fulcrum point being where the gas block meets the barrel. The piston will represent the force applied against the lever. The greater the distance that the force is applied from the fulcrum point, the greater the force is amplified by the lever… You know what, if you need more, just go read the Wikipedia entry on mechanical advantage.

But AKs aren’t really designed as precision firearms, you say? Exactly. So why trade reliability for accuracy when you can have both? Using AK magazines will improve the reliability of a 7.62×39 AR, which is an inherently more accurate platform. Cheap ammo, more accurate, and still reliable. That’s why. End of story.

I like the idea of running inexpensive 7.62x39mm ammunition in an AR, however, there is one considerable hurdle: Finding reliable magazines. The AR-15 was designed around a bottle necked cartridge with very little taper from base to shoulder, thus, the magazines and magazine wells are fairly straight. Conversely, the 7.62x39mm cartridge has a very aggressive taper from base to shoulder, thus, the magazines will need a very aggressive curvature to keep the rounds oriented correctly within the magazine. This does not bode well for 7.62×39 AR magazines… They exist, but they are fugly and uncommon.


However, AK magazines are less fugly, and very common. I digress…

So, how does one find an AR that accepts AK-47 magazines?

The idea of running AK-47 magazines in an AR platform is not entirely new. Some tin-foil hat wearing conspiracy theorists speculate that the concept first appeared during the Cold War. The US military liked the idea of domestic weaponry that special forces could use in enemy territory without leaving much of a footprint. Since the US’s biggest enemy at the time was the Soviet Union, the cartridge of choice was the 7.62x39mm. Military engineers would eventually come to understand that the AR did not necessarily like to feed 7.62×39 through standard AR magazines, and the magazine well design did not leave much room for innovation. Thus, they developed an AR that took AK-47 magazines. Not only would this design allow US special forces to use enemy ammunition, they could commandeer enemy magazines as well. According to the ‘basement historians’, several prototypes were developed, a few companies actually made the weapons under US military contract, but the public has never been made aware of the extent of their existence or usage.

Regardless of that story’s validity, there is a good chance that such weapons did actually exist, even if in small markets, in the latter half of the 20th century. Albeit, I haven’t been able to find much history on the topic, so we will have to skip ahead in time.

Fast forward to the age of the internet. In response to a US Government request in 2001, Knight’s Armament Company (KAC) developed an M4 variant that used AK-47 magazines called the SR-47. Only seven of them were produced: Six went to the the United States Special Operation Command (USSOCOM), and the seventh was kept in the KAC museum. Only myth and legend knows what USSOCOM did with the SIX they received.

Despite the low profile nature of the project, word got out of such a monstrosity existing, and interest began to swell.

A small niche market emerged in the late 2000s for hybridized weaponry and ARs chambered in calibers OTHER than .223 Remington or 5.56 NATO. The market saw an explosive interest in calibers like 6.8 SPCII, .300 Whisper, and .204 Ruger, and the AR-15 made a convenient platform for such calibers. Rumors about firearms like the Magpul Masada, the Robinson XCR, FN SCAR, and other multi-caliber weapons were also born of this era; all of which were proposed as being convertible to accept AK-47 magazines with parts the manufacturers would sell aftermarket. Of course, none of that actually happened (*COUGH->ACR<-COUGH*).

Remington/Bushmaster took a real big dump on that idea…

In the lesser mainstream areas of the internet, images and documentation of ARs chambered in 7.62×39 began to find their way around the discussion forums, leading to a growing interest in pursuing the concept of ARs using AK-47 magazines. However, most of the discussion was just… well… discussion. Very few of the people talking about it had any expertise in firearms design or had the machinery to develop such a beast. But like with any growing interest, a market began to form…

Some obscure examples of early AR-AK hybrid receivers came out of this interest. The earliest players I could find on the civilian market came from companies like Vulcan Arms with their V62 and Special Weapons Inc. with their AR47. Probably the most intriguing was the Hydra receiver made by MGI. It was a modular AR receiver with several magazine well options, including wells for AK-47 magazines, AK-74 magazines, Thompson sub-machine gun magazines, Sten magazines, and even M1A magazines. The platform was unbelievably expensive, however, and their reputation had yet to develop any widespread notoriety. MGI still makes and sells the Hydra today, and albeit an exquisite platform, their stuff is still too rich for my blood.

The biggest downside with all of these early designs was that not one company offered a compatible upper receiver to fit the large AK magazine dimensions. Custom machining had to be done to mil-spec uppers in order to work with these companies’ lowers, so many people were turned off by the time and money investment.

The real advancements came in the 2010s. Rock River Arms (RRA) brought the LAR-47 to the market, but they didn’t sell individual parts, requiring you to buy the whole rifle, which was (and still is) expensive. In addition, the internal parts to the LAR-47 (like the bolt, bolt carrier, firing pin, etc.) are proprietary, so putting a piston system in it is completely out of the question. Don’t get me wrong;  it is a very good gun, but it doesn’t work for my project.

CMMG then came out with the MK47 Mutant, but alas, the platform is loosely based on the AR-10 receiver (albeit actually shorter than a standard AR-10), not an AR-15. I will admit that albeit expensive, the CMMG MK47 Mutant is currently the most popular AK-mag-fed AR platform on the market. And although it’s a fantastic platform, the modularity of the gun is reduced because of the not-AR-15/not-AR-10 design (which means I can’t put a piston on it).

The freedom of the AR’s beautiful modularity seemed to evaporate as AK mag accepting ARs became available… but then a savior appeared in the mist: Palmetto State Armory…

The PSA announced its KS47 at the 2016 Shot Show. It, like the RRA LAR-47, is an AR-15 platform that accepts AK-47 magazines, but for a lot less money. While you can buy a fully assembled and functioning KS47 directly from PSA and other online firearms retailers, PSA did one better than Rock River Arms… The majority of parts and internals were exactly the same dimensions as standard AR-15 parts (save the bolt carrier, but standard bolt carriers can be modified)… and they released stripped upper and lower receivers… That’s right. PSA allowed the consumer to build their own AK magazine fed ARs. Now that is what I’m talking about!

Today, you can purchase (when they are actually in stock) all of the individual components to build a KS47 of your own directly from Palmetto State Armory. Judging by the stripped KS47 upper and lower, the quality of craftsmanship is fantastic. Both receivers are milled billet 7075-T6 aluminum, and fit solidly together. They also sell a modified bolt carrier group optimized for 7.62x39mm and proper clearance for AK-47 magazines. If you want to build an AR that accepts AK-47 magazines, it’s my humble and incredibly biased opinion that the PSA KS47 is the way to go.

Go to Chapter 2: The Build


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