Primary Weapons Systems MK111 2-M AR Pistol

Primary Weapons Systems has been around since 2008. Their claim to fame is a unique type of gas piston AR-15 that incorporates a long-stroke gas piston system into its action. The Primary Weapons Systems’ design operates similarly to the gas piston system of the Kalashnikov. The only difference between a PWS and DI (Direct Impingement) AR-15 bolt carrier group is the gas key. On PWS units, this part of the bolt carrier connects to a piston and probes forward into the upper receiver as one solid piece.The PWS MK111 Mod 2-M AR Pistol, one of PWS’ go-to tactical offerings, takes full advantage of this proprietary long-stroke piston system. The MK111’s bolt is interchangeable with any other new mil-spec AR-15 bolt chambered for 5.56 or .223 Wylde. AK-47 reliability with AR accuracy, what’s not to like?

Primary Weapons Systems MK111 Mod 2-M

The Primary Weapons Systems MK111 can be purchased as a large-format AR Pistol or as a short-barreled rifle (SBR).

MK111s are assembled with an 11.85-inch nitrided barrel that sports a 1:8 twist rate. Its chamber is profiled for the ubiquitous .223 Wylde which boosts both accuracy and reliability. The business-end of the MK111 includes a PWS FRC 2-Port Compensator, which is compatible with the Rearden Atlas suppressor mounting system. Shrouding the barrel is PWS’ own “Piclok” handguard. Piclok is actually pretty neat, because it combines both Picatinny and M-LOK mounting surfaces into a single ergonomic handguard.

Fortunately, Primary Weapons Systems designed the Mod 2-M lower receiver to be “southpaw” friendly. It features a right-side bolt catch in addition to a left-side magazine release. In addition, these lowers are built with a PTFE coated mil-spec trigger. It’s nicer than the average factory trigger single-stage AR-15 trigger. However, because I’m a bit “particular” when it comes to AR-15 triggers, I swapped it out for Rise Armament’s “Blitz Defense” single stage trigger. This Rise Armament unit provides me with a smooth trigger pull, a quick reset and a slightly wider trigger blade. Best of all, the Blitz Defense is set at a 4.5 lbs pull weight, which I find ideal for tactically-driven AR-15s.

PWS MK111 Mod 2-M Round Count To Date

At the time of this writing, I’ve personally fired in excess of over 7,000 rounds through my Primary Weapon Systems MK111 Mod 2-M. The majority of my round count has been fired with a mounted suppressor too. Compared to traditional direct impingement, PWS’ long-stroke system is designed to run much cleaner and cooler. This is partially due to the fact that the system vents excess gas near the gas block and away from the upper receiver/chamber area. As a reader, you’re probably aware how adding a can to an AR-15 tends to increase backpressure. On DI guns this means that even more gas and soot is forced back to the chamber area. Piston systems really help to cut down on this. Also, if you’ve followed any of my previous articles, you’re likely aware that I like to push the limits of weapons and equipment before trusting my life to them. Yes, I have trust issues! But I was also a dumb private in the Army, and a new boot rookie Deputy Sheriff once. Breaking stuff with relative ease is one of my specialties, especially after a friendly visit from The Good Idea Fairy.

From all of that ammo I’ve fired through my personal MK111 Mod 2-M, I can’t honestly remember having any noteworthy issues. My AR pistol has been nothing but reliable and accurate, and I really can’t ask much more from it. I’ve personally seen a PWS MK116, which also shares the same long-stroke gas system as the MK111, that 5,000 rounds fired through it. It hadn’t been cleaned and it was filthy, but that MK116 worked just fine. I’d encourage you to check out more of my exploits with my MK111 Mod 2-M here, where I share my experiences at a recent Thunder Ranch class.

Mounting Optics & Lights

I opted to go Holosun for all of the optics on my Primary Weapons Systems MK111 Mod 2-M. My primary optic is AEMS-PRO-X2-RD. This sturdy unit has a 2 MOA center dot and an optional 65 MOA outer circle. for choices of reticles. The AEMS features many of Holosun’s signature details, like its Solar Failsafe and shake-awake. With the Holosun AEMS, everything is contained inside of a Grade 5 titanium housing. Grade 5 titanium has double the tensile strength and likely 5 times the fatigue strength of 7075 series aluminum. To boost my primary optics’ capabilities, I opted for Holosun’s HM3XT fixed 3x power magnifier. It features a factory flip-to-side mount, and this unit provides me with additional target identification abilities. It goes without saying that it will let me shoot further with the MK111 Mod 2-M and the AEMS too. This red-dot and 3x fixed magnifier makes a great combo. It’s also a nice alternative to shooting with an LPVO.

Every duty or defensive firearm ought to have a light. Beyond optics, Holosun has also ventured into weapon lights too. While I’m not ready to call Holosun tactical lights “Surefire” or even “Cloud Defensive” level yet, my Holosun RAID tactical light is growing on me. It’s pretty bright at 80k Candella and 1k Lumens. It’s durable and handy light; I can personally attest to it receiving several paint transfer marks all over its body from banging into door jambs and other “obstacles” during CQB training. The Holosun RAID still works just fine and though it ships with a small pressure pad that allows for activation, I swapped it out for the Modlite ModButton from Unity Tactical. It’s smaller and suits my needs better.

MK111 Mod 2-M + Holosun IR/Laser

It’s a great feeling being able to see in the dark. For nightvision capabilities, I mated Holosun’s IRIS-GR3. This device is their new PEQ-style dual laser and IR illuminator. The IRIS-GR3 has an infrared (60mW IR VCSEL) illuminator, along with a visible laser pointer (available in green or red), as well as an infrared (IR) laser pointer. Like the RAID tactical light, everything is encased inside of a 7075 T6 Aluminum housing. This thing is small and light, weighing only 6.4 ounces. Thus far, this has worked great and has held up to abuse too.

Suppressing The MK111 Mod 2-M

I mounted PWS’ own BDE 556 Ti Suppressor. This 3D printed titanium silencer contains removable baffles for easier servicing at the end-user level. Its design allows users to customize the length and noise reduction to their liking. The PWS BDE 556 Ti has taper threading to prevent carbon locking and loosening between the baffles and features a universal ⅝ x24 TPI thread pattern for mounting. PWS claims that the precision engineered baffles strategically minimize backpressure, therefore enhancing firearm performance. Even after my frangible ammo debacle that I experienced at Thunder Ranch, the BDE 556 Ti Suppressor has served me well. With frangible ammo, I noticed it was rather sparky. Some of this is to be expected for a titanium silencer that is well “broken-in” like mine.

How It Shoot?

After my experiences with it, the PWS MK111 2-M pistol is an exceptional choice for self-defense or plinking. But results also matter, so I also made sure to group this upper too. I’ll admit I wasn’t shocked much with the results because I expect a tac-driving workhorse from Primary Weapons Systems. At 50 yard with the PWS BDE 556 Ti attached, I easily nailed a 0.8-inch 3-round group with Black Hills 77-grain BTHP ammo. Granted this was only 50 yards but there were no benches to shoot from. Know that I shot this group standing while using a tripod in the middle of a field (with a safe backstop). Therefore, I’ll call those great results. Palmetto State’s 77-grain AAC OTM printed a 0.9-inch group as well.

The PWS MK111 2-M is quite soft-shooting. If adding this upper to an existing lower, make sure you use an H2 buffer–what Primary Weapons Systems recommends. After years of shooting with PWS rifles and trusting my life to them, I heartily recommend them.

PWS MK111 2-M AR Pistol Specifications

Caliber: .223 WYLDE
Magazine Capacity: 30+1
Trigger Weight: Approx. 4.5lbs
Barrel Length: 11.85” w/ 1:8 twist
Weight: 6.2lbs (unloaded and no optic)
Optic: Holosun AEMS-PRO-X2-RD MSRP $470.58 / Holosun HM3XT Magnifier MSRP $388.22
Holosun IRIS-GR3 MSRP: $1058.81
PWS BDE 556 Ti Suppressor: $999.95
MSRP MK111: $2099.95 (AR pistol only)