Comments on Primary Weapons Systems (PWS) and its long-stroke piston?

[Jaywalker]

I can't find anything of note in P-F with regard to PWS's long-stroke piston models. (Generally, when I can't find something on P-F I take it to mean "It's not worth talking about," but the PWS comments I find elsewhere are pretty uniformly positive, so I thought I'd ask.)

I've pretty much decided to make a strong effort to reduce the noise and blast effect of rifle/carbine by moving to 100% suppressor shooting. I think I'd rather have a separate carbine for this, preferably one that I can keep a little cleaner than a suppressed standard direct impingement carbine. I'm considering an AK variant, so why not consider a piston AR? In a piston AR I want a company that will be around awhile as I'll be tied to their proprietary product, a carbine that's reliable and reasonably accurate and easy to suppress. Cost is an issue, but less so than the first three requirements. I understand the AK is more reliable with its long-stroke piston than the SKS and its short-stroke, so if that doesn't hold true in the AR world I'd like to know.

I'm also considering LWRCi but I've I've been able to find data on them, so in this thread I'd like to learn about PWS. Please tell me what you think I should know.

[WobblyPossum]

Aaron Cowan is a fan of PWS. He partnered with them to release a Sage Dynamics edition rifle. He’s since partnered with SOLGW for a Sage Dynamics gun but said in a recent video that he still very much liked the PWS guns.

[Suvorov]

I have a MK216 and I absolutely LOVE it! Other than a few ammo related issues early on it has been 100% reliable with just over 2000 rounds down the pipe. I've shot sub MOA 5-round groups with it out to 300 yards (and some bigger) so I would say it is right around a 1 MOA rifle. Had one issue with the bolt catch plunger seizing up on me and I stripped the screw that held the bolt catch in place which required a return trip to the factory, turn around was quick.

As far as shooting goes, it is a nice shooting rifle with a very smooth recoil impulse. Hard for me to know how much of the recoil is tamed by the brake and how much by the gas system but it is every bit as soft shooting as my M1A. Really just an enjoyable and accurate .308 rifle that you can shoot all day.

I haven't ever had the opportunity to run it suppressed so can't offer anything on that.

I don't have any experience with their 5.56 offerings but given my experience with the 216 they would be my first stop if I was in the market for a piston driven AR in 556. My primary AR is a SIG516 which uses a short stroke piston configuration similar to the LWRC and HK416. It's been super reliable as well with more rounds through it that my PWS. It's hard for me to determine which system is more reliable, my gut tells me that both are on par with each other. The PWS operating rod is two parts like the AK but it is far less robust than the AK being similar in diameter to gas tube on an AR and the two pieces fit together rather than are pinned like the AK . The one advantage I see with the long stroke over the short stroke is the recoil impulse as the PWS vents the gas in a metered fashion (explained in their videos) while my 516 has a fairly sharp impulse (then again I am comparing a 762N gun to a 556 gun). There are also a few less parts in the PWS gas system than the 516s so that might also be better?

ETA - and yeah, the Slavophile in me smiles to know that inside of my AR is the the heart of an AK.

[Default.mp3]

I did not notice my PWS MK110 Mod 1 being any cleaner than my DI AR-15s when suppressed, though all my AR-15s that I shoot often are tuned for suppressed shooting. Even with the suppressed setting on the gas block, it was severely overgassed when using a SureFire SOCOM556-RC (it was able to feed PMC Bronze on position 3 of 4 of the gas block even without a suppressor, despite position 3 being nominally for suppressed .223 Rem use, while used in conjunction with a Sprinco green spring and a Slash XH 10 oz A5 buffer). I never really shot it for groups, but I remember accuracy being acceptable with Gold Dot. Bolt lugs sheared at ~2200 rounds shot.

PWS customer service was always excellent and responsive. They replaced my bolt for free, and also replaced the gas block adjustment so that the gun would be less overgassed, which actually led to it being undergassed for unsuppressed shooting, which they also rectified. However, I still found my tuned DI guns to be more pleasant to shoot suppressed in terms of gas-to-face.

I would suggest simply building or modifying a DI gun tuned for use with your suppressor, rather than messing with a piston gun, for the sake of commonality of parts and staying out of a proprietary ecosystem. My PWS gun was very nice, but ultimately I did not see any advantage offered by it. Alternatively, there are starting to be much more low backpressure cans becoming available, so you could pick up one of those and use them with your existing DI guns without modification.

[LukeNCMX]

Unpopular opinion i’m sure, but I never understood piston ARs outside of austere environments with a suppresor.

Run a light grease instead of oil, wear eye pro, and use one of the numerous charging handles with a gas deflector.

Also, take the time to time to setup a proper buffer weight that can run suppressed or unsuppressed.

The weight and balance benefits of a DI gun alone are 100% worth the increased cleaning frequency.

My Mark 18/socom mini/A5H4 runs like an absolute dream.

[Jaywalker]

However, I still found my tuned DI guns to be more pleasant to shoot suppressed in terms of gas-to-face.

Did the gas-to-face come out the back of the receiver or the ejection port? This was the standard charging handle supplied by PWS?

[Default.mp3]

Did the gas-to-face come out the back of the receiver or the ejection port? This was the standard charging handle supplied by PWS? Back of the receiver. This was with a standard AXTS Raptor, the Freedom Bone (now the Raptor SD), and the Geissele SCH.

[Jaywalker]

Back of the receiver. This was with a standard AXTS Raptor, the Freedom Bone (now the Raptor SD), and the Geissele SCH.

They're putting the Raptor on the MK116 MOD 2-M now, I understand.

[snow white]

I've owned a pws for some time now and have used it in many classes. I really love mine and it has proven to be 100% reliable for me. It's definitely a bit heavy compared to a DI gun of the same size but boy is it nice with a can.

[crosseyedshooter]

I shoot left-handed so I really went looking for less gas blowback with a suppressed AR. I have the latest iteration of the Mk111 Mod 2 upper with the three-position gas block. Paired with a Sandman K, it’s very pleasant for me to shoot but there’s definitely a little puff of gas coming back down the barrel and out the ejection port. The weight and balance feels similar to a medium contour barrel DI upper. One thing to keep in mind is PWS doesn’t sell the special barrel nut wrench needed to fully service the upper and pretty much every part is proprietary. This upper will only last as long as the company.

[Suvorov]

This upper will only last as long as the company.

That is probably my biggest concern with PWS although in fairness, they are probably just as likely to last as LWRC and SIG is has already stopped support for its 516 and HK clones are unobtainium for most so if you are looking for a piston AR you are kind of at the mercy of the manufacturers. I guess one more plus for the DI side.

[Stone]

Unpopular opinion i’m sure, but I never understood piston ARs outside of austere environments with a suppresor.

Run a light grease instead of oil, wear eye pro, and use one of the numerous charging handles with a gas deflector.

Also, take the time to time to setup a proper buffer weight that can run suppressed or unsuppressed.

The weight and balance benefits of a DI gun alone are 100% worth the increased cleaning frequency.

My Mark 18/socom mini/A5H4 runs like an absolute dream.

Actually all AR's are piston operated, one utilizes it internally and the other externally.

[Stone]

That is probably my biggest concern with PWS although in fairness, they are probably just as likely to last as LWRC and SIG is has already stopped support for its 516 and HK clones are unobtainium for most so if you are looking for a piston AR you are kind of at the mercy of the manufacturers. I guess one more plus for the DI side.

I understand your concern and I own and build DI's and piston rifles. I do know that LWRC torture tested their external piston system many years ago trying to get it to the point of failure. The results after 80K rounds: 4 barrel swaps, 10 piston return springs... The Rod, intermediate rod, nozzle and cup were still running strong after 80k rounds but were retired because they felt at 80k rounds it had more than stood up to what they could throw at it. Some of that was full auto as well. Their barrels are rated at 20k rounds so when they started keyholing they put on a new barrel. That intell was straight from Darren M. the original VP at LWRC. Both platforms have pro's and con's like everything else, its up to the end user to determine which is best for their scenario as mission drives equipment.

For clarity: Are you stating that LWRC has stopped for support for their rifles? IE- piston parts? Thats how it reads when I read your post...

[Suvorov]

For clarity: Are you stating that LWRC has stopped for support for their rifles? IE- piston parts? Thats how it reads when I read your post...

No - I am stating that SIG has stopped support for the 516 and that any piston AR requires you becoming married to the manufacture for future support no matter how unlikely the gun is to fail.

[Stone]

No - I am stating that SIG has stopped support for the 516 and that any piston ARnrequires you becoming married to the manufacture for future support no matter how unlikely the gun is to fail.

Tracking... TFC

[JclInAtx]

As another option LMT makes a piston version of the mars-l. I have no personal experience. They cost less than an HK but more than pws.

https://lmtdefense.com/product/mars-l-5-56-piston/

[Jaywalker]

So far it doesn't appear there's anything wrong with PWS except that it's proprietary and if the company dies, then so does the support for the rifle or upper. The same applies to all of the piston uppers, so there's no advantage here, unless you correctly guess which will be the last company standing. I have no faith in my ability to do that.

A recurring issue with AR pistons is "why bother?" The DI system is standard. I suppose it comes down to how much I hate cleaning, though Default.mp3 and LukeMCMX don't see a benefit, while others think PWS is nice, with a suppressor and without.

How would you set up a DI rifle for suppressor? What do you absolutely need. Just grease the bolt? Is an adjustable gas block and a special charging handle absolutely necessary?

[Default.mp3]

How would you set up a DI rifle for suppressor? What do you absolutely need. Just grease the bolt? Is an adjustable gas block and a special charging handle absolutely necessary?Some way to restrict the gas if you're not going to use a flow through suppressor. You can do that with an AGB, a gas block insert, adjustable carrier, restricted gas tube, etc. The charging handles don't seem to really do much in general, IME, and only address gas-to-face without doing anything for the accelerated wear on components or gas out of the ejection port.

For a dedicated gun, I would say that a BRT EZTune gas tube would be the easiest solution: https://blackrivertactical.com/WP/Adjustable-Gas-Drive-c6464009

For my guns, my 11.5" uses a gas block insert along with an LMT e-BCG. My 14.5" uses an AGB with an LMT e-BCG. Both use a Sprinco Green with an A5H2.

Or, just get a flow through suppressor and not have to worry about any of that. They're not without their own drawbacks, but you'll have to weight the pros and cons yourself.

[crosseyedshooter]

How would you set up a DI rifle for suppressor? What do you absolutely need. Just grease the bolt? Is an adjustable gas block and a special charging handle absolutely necessary?

Ideally, you'd have a barrel with gas port location and size specific to running with that suppressor. That means it probably won't have enough gas to cycle without the suppressor on it. If it has to cycle without the suppressor, it would need a larger gas port or longer dwell time which becomes over-gassed with a suppressor. The one exception could be the flow-through type suppressors that are starting to come on the market. I think Huxwrx (OSS) was the first to commercialize it, but other companies seem to be coming out with their own versions.

The Noveske switchblock was a convenient adjustable gas block with just two settings but they can only spec two gas port sizes and they either work for you or don't.

[Magsz]

I really wish the myth that external piston guns are cleaner would die. That is absolutely, 100% not the case. External piston guns shit where they eat via blowback right down the damn barrel.

External piston guns introduce a host of other issues not found in internal piston (DI guns) such as, Piston pop, proprietary parts, extra weight, carrier tilt etc. They are not "better" than a DI gun, they are just different. Pistons excel in short barrels, ie more violent operating systems and that's about it.

PWS is definitely one of the best piston systems on the market due to its long stroke design. The design is very, very well thought out and as a complete system, it offers solutions to most of the common issues associated with adding on components to a very simplistic existing system, ie DI.

I have run a MK111 Mod 2, MK111 Pro, MK107 mod 2 (7.62X39) and MK111 Mod 2 (7.62X39).

The 5.56 guns never saw a high round count so I can't really say much about them other than the fact that they had a bit of a "stout" recoil impulse compared to my DI guns. I enjoyed the adjustable gas block and never had any real issues tuning them for suppression. The caveat being, I only ran those 5.56 guns with .30 cal relatively low backpressure suppressors so tuning was pretty easy.

The 7.62X39 cal guns were and are AWESOME. That mk107 is an absolute pussy cat to shoot and I really do adore humping it around on hog hunts.

Overall, I think that PWS can confidently fall into the realm of consideration for a premium AR. Their components, machining and design all scream "well made" and i've never had an issue with their customer service. Granted, i've never had to use it for repair purposes but every time I call with a question they are courteous and extremely helpful.

IF you want a piston gun just because, or you like the PWS design, buy it without hesitation. It is one of the best systems on the market in the piston realm and as a functional firearm, it doesn't really suffer from any real negatives.

Don't however, buy one because you think you need one. You can accomplish the same end goal with a properly set up DI gun.

[Jaywalker]

... myth that external piston guns are cleaner would die. That is absolutely, 100% not the case.
...
Don't however, buy one because you think you need one. You can accomplish the same end goal with a properly set up DI gun.

I've seen comments that a piston is cleaner and I've seen others, including Magsz's, that a piston does not help keep the rifle cleaner. What's the consensus?

[Magsz]

I've seen comments that a piston is cleaner and I've seen others, including Magsz's, that a piston does not help keep the rifle cleaner. What's the consensus?

Not to be a dick but...YOLO...

Whoever thinks a piston is cleaner doesn't shoot their gun(s).

They are NOT cleaner in any meaningful way. Short of lab testing which may prove that a piston introduces marginally less crud to the chamber area, I believe whatever decrease there may be in fouling is largely inconsequential. Since an internal (di) piston has two exhaust holes, ie the gas tube AND the barrel, I can believe that more blowback does enter into the system. Having said that, it's never been an issue for me and not something I could ever quantify.

There's been extensive testing on this in regard to mean time between failures that the military did and traditionally, the HK416 outclassed the M4 but once the magazine issue was sorted, soldier satisfaction with the M4 has been VERY VERY high.

Lube your shit and run it.