Home Reviews Primary Weapons Systems MK1 Piston AR-15 Review

Primary Weapons Systems MK1 Piston AR-15 Review



The debate over the better platform, the AR-15 or the AK-47, has been going on for ages. It’s an argument that may never be laid to rest. The MK1 series, developed by Primary Weapons Systems, is the best of both words. It has the ergonomics and accuracy of the M4/M16-type carbines and rifles and the reliability of the AK47. This explains why the MK1 series has gained wide popularity with security personnel, law enforcement and civilians alike.


With the professional operator in mind, the PWS MK1 series platform was developed to be superior to both the direct impingement operating system and the previous offerings of piston-driven operated M4/M16-style weapons. The PWS proprietary operating system utilizes an operating rod that is attached to the carrier and a floating head piston. This addresses reliability and performance issues as well as reduced carrier tilt, cam pin wear and carrier bounce which is common with other piston driven AR-15s on the market.


Unlike other gas piston systems, the MK1 series rifles are not nose heavy and actually seem lighter than the conventional direct impingement systems. Moreover, the cleaning of the PWS MK1 platform after a day at the range is dramatically easier and faster than with a traditional direct impingement system AR. An innovative hand guard system utilizes a proprietary non-free float system that allows the user to replace individual rails as needed without removing the barrel nut or other rails. This system allows the user to attach numerous picatinny rail mounted equipment as they see fit, such as lights, laser aiming devices and optics. There are no unnecessary gas adjustments at all with the PWS MK1, it has only one moving assembly making it very easy to use and operate.


Caliber: 5.56 NATO
Weight: 6 lbs, 15 oz (3.15 kg)
Overall Length: 32.9″ (83.5 cm)
Barrel Length: 16.1″ (40.9 cm)
Barrel Specs: Hard Chrome Lined, Button Rifled, 1:8 twist

Hard Chrome Lined, Button Rifled, 1:8 Twist Barrel
BCM Gunfighter Enhanced Charging Handle
PWS Mil Spec Upper and Lower Receiver
PWS Enhanced Bolt Carrier Group
Micro-slicked Internals
Magpul XT Rail Panels
Magpul MOE® stock and grip
Magpul MBUS® sights
Magpul PMAG® 30


The PWS FSC compensator does an excellent job of keeping the rifle leveled downrange and reduced muzzle flip drastically, making follow up shots very easy.


BCM Gunfighter Enhanced Charging Handle
This charging handle is a convenient addition to the PWS MK1 because it allows the user (right handed) to be able to quickly and easily charge the rifle without removing your strong side hand.



Cleaning of the of the MK1 series system is simple and fast. The bolt carrier group and piston rod are one piece (just like with the AK47), which makes it very easy during disassembly when field striping and cleaning. Utilizing the proven long stroke piston system, the MK1 series greatly reduces fouling in the action of the weapon making it as reliable as the AK47.



We put close to 800 rounds through the MK1, we used everything from green tip 5.56 to Tula steel cased .223 and PMC Gold. It reliably feed and fired everything we used without a hitch. Accuracy was very respectable, the above target was from firing offhand at 75 yards after sighting in the Magpul sights. Note, there’s two bullet holes in the lower grouping.



This review took us a few months to complete, we don’t believe in rushing our reviews just to get them out there. We wanted a complete analysis of the weapon system, and to try to find something we did not like about the product. However we weren’t able to find anything we really didn’t like. In the months we’ve had the rifle and out of the multiple range sessions, and even a carbine class, the PWS MK1 functioned flawlessly. It felt very solid, yet surprisingly lightweight and easy to carry for extended periods of time. If there is any single negative to the PWS MK1 it may be the price point, the MK116 starts at $1650. It’s a price point that may deter new shooters or those on a budget, but for all that you get it’s definitely not overpriced.

Simply put this AR platform is outstanding right out the box, the MK116 is good to go. I strongly recommend this rifle platform for Military/Law Enforcement, home defense, sport, and competition shooting. Its simplicity, ease of use, light weight, and most of all the reliability makes it one of the best AR-15s I’ve ever used. PWS got the formula right when they created a very well balanced rifle, they definitely should be considered a real contender as the next premier AR platform developer.

For more info, check out the entire PWS product line at PrimaryWeapons.com.

Check out a few more photos of the PWS MK1 AR-15 below.

Check out all of our past reviews at our Reviews Page.






Bolt Carrier

Gas Block

Buffer tube



  1. Enjoyed reading this blog; lots of great information and the pictures are excellent. I was looking into purchasing a piston driven AR-15 a little over a year or so ago, after seeing one featured in Guns and Ammo, but the information was not as detailed or available at that time. Having served in the Army during Desert Storm, I saw first hand how easy it is to foul a M-16, and how dependable and rugged the AK-47 was. So when I heard that there were plans for a rugged AR, I just couldn’t wait. Thank you for the blog and information, add me to your fan base!

    • Thanks Chris, we’re glad to have you. The PWS piston AR has still been flawless since we published this review. We’re big fans of their ARs after seeing just how well they functioned. They have since improved upon their design as well.

  2. Is anyone aware of any reviews of Piston AR15s? How does the Robinson Arms and Rock River pistons systems compare?

    • Hi Eric, haven’t had a chance to review rifles from any of those companies. We do have another piston AR-15 review in the works coming soon however.

  3. I have the CSAT version and I love it. This rile is fantastic. The only problem I have with the PWS business is they never notified me of the problems they were having with the rubber buffer at the back of the buffer tube. I found out about the issue from Paul Howe. After contacting PWS they sent me a replacement in about two weeks. The rubber buffer on my rifle was also damaged only after 200 rounds. Not sure what would have happend to the rile if I did not replace the rubber buffer in time but I know I would have been really pissed off if the rilfe got damaged.

  4. Nice review- looks like a great carbine.

    In the 3rd to the last picture, I can see why you were wearing gloves and using a vertical foregrip.

  5. To my understanding  you do not need to remove the charging handle,a simple wipe with a Q-tip should be adaquit because this piston system receives minimal gas exposure. Furthermore, The piston system is not adjustable, think of the reliable AK47 piston system but in an AR platform.


Please enter your comment!
Please enter your name here