Panzer Arms USA AR-57 Conversion

Tactical Transformer
; .

The Panzer Arms AR-57 transforms any standard AR-15 lower receiver assembly into a radical 5.7x28mm hotrod. It’s a lightweight and maneuverable utility carbine.

One of the biggest reasons for the AR-15’s enduring popularity is its unrivaled modularity. Modularity is the holy gospel in modern gun design. Think of it like Tinker Toys, LEGOs or GI Joe action figures, only louder. By mixing and matching components and accessories, one basic AR-15 chassis can potentially be all things to all users.

This deep into the Information Age, the basic AR-15 can be everything from a pistol-caliber submachine gun to a belt-fed light support weapon. Now thanks to Panzer Arms, your favorite AR lower receiver can also transform into something altogether fresh and new.

The Panzer Arms UltraLight Tactical 5.7x28mm upper receiver assembly is a self-contained drop-in upper half compatible with any mil-spec AR-15 lower receiver. This nifty rig feeds from standard FN P90 50-round box magazines and adapts your favorite AR lower to fire the zippy little 5.7x28mm Personal Defense Weapon (PDW) round. This thing is slicker than snot and cooler than polar bear boogers.


The non-reciprocating charging handle folds out of the way when not in use.

Swapping the charging handle around for left-sided operation is not a terrible chore

The magazine release is a bilateral pivoting lever easily
accessed from either side. Below, the Panzer Arms AR-57
is weird, but the good kind of weird.

The Details

To understand how this rascal works, you need to forget everything you know about the AR-15. The 50-round translucent polymer magazine mounts lengthwise to the top front of the assembled weapon. To install the mag, set the base at the front of the rifle and press down until it snaps into place. The magazine release is a handy pivoting bilateral lever at the near end of the magazine. The top-mounted magazine precludes mounting a long optic, but it is pretty easy to access.

Magazine changes are more cumbersome than the same exercise with a conventional M4, but the box does carry a full 50 rounds. Learning a new manual of arms for this familiar platform was great fun. The gun ejects downward through the AR-15 magazine well. Interestingly, you can remove the spring and follower from a polymer M-4 magazine, saw off the feed lips and use the resulting box fitted in the magwell as a handy brass collector.

The magazine itself is radically advanced. Rounds ride in a double-stack configuration from front to rear. The last round in the stack pivots 90º under spring pressure to align with the bore axis. Each subsequent round snaps in place immediately prior to feeding. Despite the high-tech nature of these magazines, spares remain quite unexpectedly cheap.

Mounting the Panzer Arms 5.7mm upper is literally painless. Punch out the front and rear receiver retaining pins, drop the new upper in place and snap the pins back. If you cannot figure it out, you likely shouldn’t be wandering about outside unsupervised.

The charging handle does not reciprocate with the bolt and comes installed on the right side of the receiver. Swapping it out to the left entails removing three Allen screws and moving the track cover over to the opposite side. The gripping bit of the charging handle folds flush against the receiver when not in use.



The AR-57 upper is blowback operated with no extraneous mechanical fluff. There is no gas system so cleaning and maintenance are simplified. The reciprocating bolt is the unit’s only major moving part.

The overwhelming majority of the world’s combat handguns use the same short recoil, locked breech, tilting barrel system. The most basic of the lot is simple blowback and you can find examples in lots of places. Open-bolt submachine guns like the Uzi and MP40 are blowback-operated firearms, as is the Walther PPK handgun. Closer to home, the Ruger 10/22 is another splendid example. In each case, the mass of the bolt and the relative strength of the recoil spring is carefully balanced against the recoil forces of the cartridge. This is what drives the AR-57 as well. It is simple, reliable and easily maintained. The AR-57 comes with its own dedicated heavy buffer to ensure the entire rig is properly balanced.


Ammo — The 9mm HoneyBadger round (above, left), the 5.56mm
is on the right. The three examples in the middle are all high-performance
5.7x28mm rounds. Magazine changes on the AR-57 are significantly
different from those of a pedestrian M-4 but the process is easy enough to learn.

At 25 meters off of a simple rest using the TRU-VISION
red dot , the AR-57 produced “ballistic art” for Will.

The Cartridge

Fabrique Nationale introduced the adorable little 5.7x28mm cartridge in 1990 in response to a NATO request for a new pistol round that offered markedly greater penetration over the standard 9mm Parabellum ball load. The proposal was for a high-velocity round that would offer greater range, accuracy, penetration and lethality over existing 9mm options. In addition to this novel little cartridge, FN also offered two radically advanced new weapons to fire it.

The FN Five-seven pistol was a polymer-framed, high-capacity service pistol that packed 20 rounds into its flush-mounted grip and offered unprecedented handheld firepower. The Five-seven was lightweight, ergonomic and effective. At the same time, FN also introduced the P90 Personal Defense Weapon.

The P90 PDW looked for all the world like a 2×4 with a thumbhole bored through the middle. This revolutionary weapon fed from a horizontally mounted 50-round box magazine and was selective-fire with a cyclic rate on full-auto of around 900 rpm. The P90 weighed a paltry 5.8 lbs. and was inimitably controllable. The U.S. Secret Service has used the P90 for its executive protection details for years now.

To their credit, FN offered both the Five-seven pistol and a semi-auto, long-barreled version of the P90 called the PS90 for sale to civilians. However, both of these guns are quite expensive. Additionally, the ergonomics of the P90 are fairly foreign to the corn-fed American shooter already accustomed to the AR-15.


The Mepro TRU-VISION electro-optical sight offers
a wide field of view and is built like a tank.


I mounted a Meprolight TRU-VISION red dot sight. The TRU-VISION is a ruggedized red dot with the features you want without the fluff you don’t. The sight runs about forever on a single CR123 battery and features simple, easy-to-use controls. There are 16 different automatic settings, two of which are NVG compatible.

The TRU-VISION sight wakes up and goes to sleep automatically. It also adjusts itself for ambient light conditions without conscious thought or active input. A throw-lever mount makes installation and removal a breeze.

Up front, I slapped on a Streamlight TLR-8G combination white light and green laser. This whole rig is about the size of my thumb and offers 500 lumens of brilliant white light along with a high-visibility green laser designator. To zero the laser, just zero the TRU-VISION red dot, pick a proper range and then adjust the fall of the laser dot to coincide with the red dot sight. The TLR-8G is tough and bright in a package that is easy to tote and won’t get in the way.


The AR-57 conversion is surprisingly straightforward:
Drop in the new upper and replace the buffer & spring.

Family Tree — (top to bottom) the Ruger LC Carbine, the AR-57
conversion, the FN Five-seven and the Ruger 57. Each of these
weapons fires the same 5.7x28mm ammo.

How Does She Run?

Wow. Just wow. The resulting lithe little rifle is all but recoilless. Imagine launching jacketed versions of .22 LR bullets at literally twice the speed of your typical rimfire. The range experience will make you weep over the high cost of 5.7x28mm ammo.

Out to any reasonable range, the AR-57 conversion shoots like a laser. It will explode discarded water-filled aluminum cans like hand grenades. The overall effect is likely about as close as you will ever get to running a real live Star Wars blaster.

Doubles and triples are dreamy, while the lack of recoil masks how truly serious this rig is downrange. Magazine changes are an acquired skill. However, once you take its measure, this gun is absolutely addictive.

It doesn’t happen very often, thanks to modern quality control, but I had a case failure during our range time together. The case separated at its midpoint and left the neck lodged in the chamber. The resulting chaos pulverized the magazine but left the AR-57 otherwise undamaged. The AR-57 is indeed built like a tank, but that’s the reason we wear eye protection.


The AR-57 feeds from an unconventional top-mounted
50-round box magazine. It stores rounds in a double-stack
fashion and then pivots them 90º for feeding.

What’s It Good For?

Don’t know, don’t care. All I can tell you is shooting this zippy little blaster is absolutely intoxicating. The AR-57 drops those hyperactive little bullets right where you want them with minimal effort.

You’d be hard-pressed to find a better Saturday afternoon plinking gun. Ringing steel with this trim little sports car of a rifle will remind you of what drew you to this bizarre sport in the first place. In a legit survival situation, the Panzer Arms AR-57 would do a serious job on bunnies or tree rats. It would work on larger stuff in a pinch if you were meticulous about shot placement. It is perfectly scaled for such villains as coyotes and similar mid-sized predators. However, the 5.7x28mm round was originally designed for social purposes.

The Secret Service uses this cartridge against bipedal threats. While there are indeed more powerful options, it is the rare bottom-dwelling scavenger that would press home an attack in the face of 50 5.7x28mm rounds. I’d feel completely comfortable with my AR-57 in a personal-defense role.

Bizarrely, there were some fairly famous photos to come out of the short-lived 2019 revolt in Venezuela showing rebels armed with AR-57s fighting government troops there. The specific example I saw was fitted to a Cerakote full-auto M-4 lower and equipped with a Trijicon SRS red dot sight. It’s tough to imagine how that thing got to Venezuela. However, they do widely employ the P90, so magazines and ammo would be readily available.

You may have scads of guns. You might have a different 5.56mm black rifle for each day of the week and spares for all the major federal holidays. However, chances are you don’t have anything else quite like this. The PS90 and Ruger’s new LC Carbine would be the next best thing, but the AR-57 has the added benefit of M-4 familiarity and modest cost. Any trigger or stock upgrades you might imagine for your favorite M-4 would be equally effective here. Fast, trim, light and cool, the Panzer Arms AR-57 transforms your favorite pedestrian AR into something truly epic.

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