Gas piston kits

[jLorenzo]

Wanting to put together a piston gun for general blasting, like keeping the BCG a little cleaner for longer. Won't be a precision gun, probably will run a red dot.
I've been looking at the Adams Arms kits. Would like to get the gas block, rod and BCG. If there is anyone making barrels with gas blocks and pistons already installed I would look at that. Already have an upper so I don't really need or want a complete upper.
Should I go mid length or carbine? I assume carbine because its a little less mass moving and a little more gas? Gonna be a 16" barrel.
Any other companies to look at or things to consider?

 

[padom]

I'm running an Superlative Arms adjustable Gas piston kit on a 11.5" 5.56 and it has been fantastic. Noticeably smoother shooting side by side with my DI 10.5 upper and cleaner to shoot suppressed. I've been running it for over a year now with lots of rounds through it and it's been fantastic

ADJUSTABLE PISTON SYSTEMS

A Retrofit Kit for the AR-15 Platform with our Patented "Bleed Off"

suparms.com

 

[Obi-WanKannoli]

Superlative Arms and Adams I think are the two good drop in options for milspec AR's. Alternatively you could always grab an LMT or LWRCI piston upper.

 

[alamo5000]

Crane: You’re not doin’ a piston gun, right?
Noveske: No.

Crane: Do you have any plans to do a piston gun?
Noveske: We have piston plans, but we don’t have any plans of putting it in production, because it’s…I don’t think it’s necessary. I’ve got piston guns here from other makers, and they’re dirty, and I don’t see…

Crane: Whadya’ mean "dirty"?
Noveske: Open up the bolt and look inside, and it’s dirty inside. The whole thing about them running clean is not necessarily…o.k., let me back up. I only run the guns with suppressors for testing when I did my comparison, and with suppressors, direct-impingement and piston-operated were both very dirty, ’cause the blowback comes to the chamber, not the gas tube. And, I’m not real happy with the piston systems that I’ve shot and examined, so it’s just to me, it’s not…

Crane: Well, the piston…the advantage for a piston with a suppressor on there is supposedly it doesn’t blow all the gunk back in your face.
Noveske: O.k., but what you’re not paying attention to is that all that crap comes back through the chamber, not the gas tube. On a piston gun or gas-impingement, the case is being extracted while the suppressor is still under pressure. Now you have all the pressure in that suppressor exiting both out the front and the back.

Crane: Right, but you’re saying the piston gun doesn’t solve that?
Noveske: It does not solve that. They’re both dirty.

Crane: So then how come you hear about guys saying yeah, when they’re shootin’ the direct gas impingement guns suppressed, or whatever, they’re gettin’ a lot of gas and particulate matter in their face, whereas with the piston, that it dissipates that a bit, or whatever.
Noveske: Maybe they had a different experience.

Crane: Hm. So, in other words, you’re saying that basically the piston doesn’t really offer any real advantage for that.
Noveske: What I’m saying, with a suppressor, direct-impingement and gas-piston both run dirty, and even a blowback gun or a delayed-blowback gun, like an H&K [Heckler & Koch], or any other operating system–I don’t really care what operating system you have–on an auto-loader, with a sound suppressor, they’re gonna’ all run dirty.

Crane: Right. Now, is a piston gun gonna’ put any less gas and particulate matter in your face, or are you gonna’ get the same amount?
Noveske: All a piston gun is gonna’ do different from gas impingement with a suppressor is reduce the amount that is coming through the gas tube. The piston gun is gonna’ eliminate that. I am not a scientist, but from my observations in shooting and examining the guns afterwards, it appears that the vast majority of the gas coming through is coming through the chamber. And, one example is go look at any of the HK91 or HK93-type rifles. Those have the fluted chamber and delayed blowback, and the cases are always black just like the case fired out of the gun with a suppressor. That’s because the case is extracting while it is still under pressure, and you have gas blowing back along the case as it’s blowing out, and covering it with carbon. And, that’s what’s happening with any autoloader with a suppressor. The cases all have carbon on them, because gas is escaping around the case out the chamber and into the receiver.

[DefenseReview received the following post-interview via email from John Noveske:
"Also, we should mention the poor choice of platform for the piston conversion on a round receiver bore as found on the M16/M4 system. All other piston type systems out there utilize a railed receiver design, like the M14, AK-47, M249, FAL and so on. The round receiver bore design used on the M4 is only acceptable for the standard op system. The carrier and bolt expand on axis with the bore under the normal gas impingement cycle, but on a piston gun, you run into off center impulse issues with carrier tilt and incorrectly designed carrier contact points. Some designs attempt to address the carrier tilt problem with over sized carrier tails and rollers. I do not believe the receiver extension should be used in this manor. I know many people are very happy with their piston weapons. This is not meant as a knock on the piston conversion systems out there, but as a philosophical dialogue focused the new physiological relationships applied to the M16/M4 platform through the introduction of an operating system which has traditionally been applied to receivers with rails for the bolt and/or carrier. I would rather see an entirely new weapon system designed for the piston from the ground up. I believe there several outfits currently working on this."]

 

[jLorenzo]

Crane: You’re not doin’ a piston gun, right?
Noveske: No.

Crane: Do you have any plans to do a piston gun?
Noveske: We have piston plans, but we don’t have any plans of putting it in production, because it’s…I don’t think it’s necessary. I’ve got piston guns here from other makers, and they’re dirty, and I don’t see…

Crane: Whadya’ mean "dirty"?
Noveske: Open up the bolt and look inside, and it’s dirty inside. The whole thing about them running clean is not necessarily…o.k., let me back up. I only run the guns with suppressors for testing when I did my comparison, and with suppressors, direct-impingement and piston-operated were both very dirty, ’cause the blowback comes to the chamber, not the gas tube. And, I’m not real happy with the piston systems that I’ve shot and examined, so it’s just to me, it’s not…

Crane: Well, the piston…the advantage for a piston with a suppressor on there is supposedly it doesn’t blow all the gunk back in your face.
Noveske: O.k., but what you’re not paying attention to is that all that crap comes back through the chamber, not the gas tube. On a piston gun or gas-impingement, the case is being extracted while the suppressor is still under pressure. Now you have all the pressure in that suppressor exiting both out the front and the back.

Crane: Right, but you’re saying the piston gun doesn’t solve that?
Noveske: It does not solve that. They’re both dirty.

Crane: So then how come you hear about guys saying yeah, when they’re shootin’ the direct gas impingement guns suppressed, or whatever, they’re gettin’ a lot of gas and particulate matter in their face, whereas with the piston, that it dissipates that a bit, or whatever.
Noveske: Maybe they had a different experience.

Crane: Hm. So, in other words, you’re saying that basically the piston doesn’t really offer any real advantage for that.
Noveske: What I’m saying, with a suppressor, direct-impingement and gas-piston both run dirty, and even a blowback gun or a delayed-blowback gun, like an H&K [Heckler & Koch], or any other operating system–I don’t really care what operating system you have–on an auto-loader, with a sound suppressor, they’re gonna’ all run dirty.

Crane: Right. Now, is a piston gun gonna’ put any less gas and particulate matter in your face, or are you gonna’ get the same amount?
Noveske: All a piston gun is gonna’ do different from gas impingement with a suppressor is reduce the amount that is coming through the gas tube. The piston gun is gonna’ eliminate that. I am not a scientist, but from my observations in shooting and examining the guns afterwards, it appears that the vast majority of the gas coming through is coming through the chamber. And, one example is go look at any of the HK91 or HK93-type rifles. Those have the fluted chamber and delayed blowback, and the cases are always black just like the case fired out of the gun with a suppressor. That’s because the case is extracting while it is still under pressure, and you have gas blowing back along the case as it’s blowing out, and covering it with carbon. And, that’s what’s happening with any autoloader with a suppressor. The cases all have carbon on them, because gas is escaping around the case out the chamber and into the receiver.

[DefenseReview received the following post-interview via email from John Noveske:
"Also, we should mention the poor choice of platform for the piston conversion on a round receiver bore as found on the M16/M4 system. All other piston type systems out there utilize a railed receiver design, like the M14, AK-47, M249, FAL and so on. The round receiver bore design used on the M4 is only acceptable for the standard op system. The carrier and bolt expand on axis with the bore under the normal gas impingement cycle, but on a piston gun, you run into off center impulse issues with carrier tilt and incorrectly designed carrier contact points. Some designs attempt to address the carrier tilt problem with over sized carrier tails and rollers. I do not believe the receiver extension should be used in this manor. I know many people are very happy with their piston weapons. This is not meant as a knock on the piston conversion systems out there, but as a philosophical dialogue focused the new physiological relationships applied to the M16/M4 platform through the introduction of an operating system which has traditionally been applied to receivers with rails for the bolt and/or carrier. I would rather see an entirely new weapon system designed for the piston from the ground up. I believe there several outfits currently working on this."]

Interesting, makes sense. I have considered most of that. I still want to try one, I think a ground up gun does make more sense. Maybe I should go with an HK or LMT.

 

[alamo5000]

Interesting, makes sense. I have considered most of that. I still want to try one, I think a ground up gun does make more sense. Maybe I should go with an HK or LMT.

Well considering that was John Noveske it probably should make sense. I was shown that interview a long time ago by people in the know...

Pistons are not a 'bad' option... but I was given solid advice from a well known figure in the gun community who has more guns than literally anyone I know or know of...and he also knows his stuff...I definitely am glad I took his advice. Originally I was going to get a piston gun...but he talked me into going DI and it didn't take long to realize the wisdom there.

Paraphrasing what he told me...'The problem with piston systems is that you are married to that manufacturer and you will have proprietary parts... I have a bunch of piston guns but the problem is on most of them the original manufacturer is no longer in business. If or rather when something breaks it's not like I can just get off the shelf parts. If things break those are getting converted to DI'

 

[jzerfoss]

Not a piston kit but....... I bought a PWS MK116 Pro upper the other day from brownells because they are on sale and there's coupons. While I've only got a hundred rounds through it I'm impressed with it suppressed. The recoil impulse is different and light in a way that is very controllable. The groups were between .75"-2" with 55/62gr ball ammo. I simply judge the amount of dirtiness/blowback by periodically looking at the ammo in the mag(how much soot is on the ammo) and comparing it to my other suppressed ARs. I can for sure tell the difference between the PWS vs my DI guns basically shitting where it eats and the PWS is hands down cleaner. I've had no issues so far and I'm currently on setting 3 because it shoots so soft and is stupid quiet but I'm sure for reliability setting 2 is where it should be.

I just figured I'd throw that option out there if it hadn't been considered.

 

[Moses42ak]

I run both the Adams and Superlative and both have been great. I don’t think you can go wrong with either one and my next one will be another Adams.

 

[Ape_Factory]

Noveske definitely wasn't wrong. I'm a fairly recent convert to piston and the bolt itself does get as dirty as a DI gun. The entire carrier is a different story though and the piston guns run cleaner in that regard. Same with the trigger, even with subs.

On my Sig Spear LT, with a low restriction flow-through suppressor, I do notice quite a bit of gas but I've only ever shot it at an indoor range with barriers on either side. I actually can't say I've noticed that with the POF P415 but we're talking a different cartridge, powder, etc...I'll have to pay more attention next time. I always am very cognizant of the amount of gas with the Sig for some odd reason.

Personally, I'd just go with an engineered piston upper and not run a conversion kit.

 

[Milf Dots]

The Sig 516 piston AR is perhaps one of the best values in piston guns, and at least one of the designers of the HK 416 went to work for Sig on the 516. It's available as a complete upper but not a kit.

 

[jLorenzo]

I run both the Adams and Superlative and both have been great. I don’t think you can go wrong with either one and my next one will be another Adams.

Why are you going Adam's over Superlative? Any advice on putting a piston upper together?

 

[Moses42ak]

No other reason than to equal out the numbers. I love the simplicity of the Adams, had the older style and switched over to the micro gas block, though the Superlative has been easy to adjust.

 

[Hoody2shoes]

Have had both the AA and SA. Superlative arms is superior to adams arms. About 7k rounds through an adams arms and about 25k through two superlative arms.
Also, my piston gun is noticeably cleaner with a can than my di gun.

My sup arms piston guns also chrono much higher than comparable di guns. My 12.5 core just chronoed black hills 77smks averaging at 2628 for a 10 shot string (2640H 2619L). I have theories as to why, but I'm not confident in them yet.

A lot of the piston issues such as weight, harmonics, and such have been solved with modern piston systems. Nothing John said is necessarily wrong but keep in mind that interview was over 10 years ago and technology has improved since his passing.

I am in no way trying to argue that either are superior to each other but people need to stop regurgitating old inaccurate information on Pistons.

Here's a few groups out of my 12.5 (black hills 77 smk's)

 

[Moses42ak]

@Hoody2shoes You state that Superlative is superior to Adams. How so?

 

[Hoody2shoes]

@Hoody2shoes You state that Superlative is superior to Adams. How so?

@Moses42ak the actual system being simpler, lighter, not needing a milspec barrel nut, and greater compatibility with handguard/rail systems.

 

[B y r o n]

@Moses42ak the actual system being simpler, lighter, not needing a milspec barrel nut, and greater compatibility with handguard/rail systems.

Actually, according to Adams site: "We recommend using a standard barrel nut or barrel nut with similar measurements for proper fit and function of the kit."

 

[Moses42ak]

You got me on the barrel nut, though I believe one could mod their barrel nut to work with the bushing. As far as the hand guard, the micro system should fit under most if not all but the most slender hand guards. I haven’t noticed any real difference in weight but maybe I haven’t paid attention. But for simplicity, I think the Adams has it. As much as I like the Superlative, I wouldn’t say the Superlative is easier. If anything it’s more difficult but once you get it set, it’s set. I guess I like them both, just differently.

 

[Hoody2shoes]

I agree with that. When I say simpler I meant the operating system. The SA is a single rod used on a strike face. The AA kit is two rods combined with a spring. The AA kit is also hollow as it feeds gas into the first op rod where as the SA kit is solid and I believe stronger.

Personally, I like all the adjustability of the SA kits. I know the rotation amount to open up with my can (3.5 revolutions further open) so it's basically just a suppressed/unsuppressed gas block at this point.

Again not knocking AA-I just strongly believe SA is the better design

 

[Hoody2shoes]

@B y r o n

I know? Are we agreeing?

People have successfully mod'ed other barrel nuts to work.

 

[jLorenzo]

Have had both the AA and SA. Superlative arms is superior to adams arms. About 7k rounds through an adams arms and about 25k through two superlative arms.
Also, my piston gun is noticeably cleaner with a can than my di gun.

My sup arms piston guns also chrono much higher than comparable di guns. My 12.5 core just chronoed black hills 77smks averaging at 2628 for a 10 shot string (2640H 2619L). I have theories as to why, but I'm not confident in them yet.

A lot of the piston issues such as weight, harmonics, and such have been solved with modern piston systems. Nothing John said is necessarily wrong but keep in mind that interview was over 10 years ago and technology has improved since his passing.

I am in no way trying to argue that either are superior to each other but people need to stop regurgitating old inaccurate information on Pistons.

Here's a few groups out of my 12.5 (black hills 77 smk's)

Do the guns have the same make barrels?

 

[Hoody2shoes]

Do the guns have the same make barrels?

Which guns are you referring to?

My 11.5 SA has a criterion hybrid and my 12.5 SA has a core.

 

[jLorenzo]

Which guns are you referring to?

My 11.5 SA has a criterion hybrid and my 12.5 SA has a core.

The two you are comparing speed between.

 

[Hoody2shoes]

@jLorenzo ahhh sorry I misunderstood.

Yes and no. It's pretty easy to find velocity info on DI guns online so getting a rough average of what they should be pushing through a barrel is pretty easy.
My 11.5, 12.5, my buddies 11.5, my other buddies 12.5 and 18 all using sup arms have had their holds curiously off from strelok. So either we ALL hit the proverbial lottery of fast barrels, or there is something else going on.

I'm planning on directly comparing a SA di system and piston system on the same gun later this year to compare velocity. I think I know why I'm getting faster velocities out of them but until I confirm it, it's just a theory.

 

[jLorenzo]

@jLorenzo ahhh sorry I misunderstood.

Yes and no. It's pretty easy to find velocity info on DI guns online so getting a rough average of what they should be pushing through a barrel is pretty easy.
My 11.5, 12.5, my buddies 11.5, my other buddies 12.5 and 18 all using sup arms have had their holds curiously off from strelok. So either we ALL hit the proverbial lottery of fast barrels, or there is something else going on.

I'm planning on directly comparing a SA di system and piston system on the same gun later this year to compare velocity. I think I know why I'm getting faster velocities out of them but until I confirm it, it's just a theory.

I see. So maybe less gas bleed off = more speed. Would be interesting to test.

 

[Hoody2shoes]

I dont think it's a "bleed off"- I think it's because the system is robbing less gas to operate it thus keeping the internal pressure higher since its not dumping gas in the upper to get it to cycle.

I came across a video on youtube where a person tested a bunch of factory uppers for velocity one of which was a pws 11.8 not only was it uncharacteristically fast, it was also by far the most consistent of the group suggesting it was maintaining the highest and most stable ratio of combustible oxygen of the group which happens to mirror my SA results

 

[TonyTheTiger]

I see. So maybe less gas bleed off = more speed. Would be interesting to test.

It's been tested quite a bit. Chrono a gun. Spin the GB upside down or backwards, or shut off if adjustable. Chrono again. It's not as exciting as it sounds.

 

[jLorenzo]

What about length? Should carbine or mid length for a 16"?

 

[Hoody2shoes]

@jLorenzo ... midlength fo sho

 

[jLorenzo]

@jLorenzo ... midlength fo sho

Why do you say that? I was thinking a carbine would be less mass moving back and forth as far as the rod goes.

 

[Hoody2shoes]

The op rod on the SA kit is insanely light. I wouldn't be concerned with mass. Still go midlength

 

[jLorenzo]

The op rod on the SA kit is insanely light. I wouldn't be concerned with mass. Still go midlength

Probably still a little smoother like a mid length DI gun compare to carbine, not as much pressure?

 

[Hoody2shoes]

Yes.

 

[hlee]

This may or may not be a useful comparison of the relative cleanliness of the different platforms. That said, I realize that this is an apples to cucumbers comparison. The AR is pistol gas while the AK is whatever length they are. The Wolverine is likely a lower back pressure suppressor than the R2 due to its larger bore diameter. The cartridges use different powders. Etc. But, after seeing how skuzzy suppressed AR brass is after firing, I was genuinely surprised at the cleanliness of the fired suppressed AK brass. AR v AK? DI v piston? Something else? Something to potentially consider…

 

[GUNNER10]

Crane: You’re not doin’ a piston gun, right?
Noveske: No.

Crane: Do you have any plans to do a piston gun?
Noveske: We have piston plans, but we don’t have any plans of putting it in production, because it’s…I don’t think it’s necessary. I’ve got piston guns here from other makers, and they’re dirty, and I don’t see…

Crane: Whadya’ mean "dirty"?
Noveske: Open up the bolt and look inside, and it’s dirty inside. The whole thing about them running clean is not necessarily…o.k., let me back up. I only run the guns with suppressors for testing when I did my comparison, and with suppressors, direct-impingement and piston-operated were both very dirty, ’cause the blowback comes to the chamber, not the gas tube. And, I’m not real happy with the piston systems that I’ve shot and examined, so it’s just to me, it’s not…

Crane: Well, the piston…the advantage for a piston with a suppressor on there is supposedly it doesn’t blow all the gunk back in your face.
Noveske: O.k., but what you’re not paying attention to is that all that crap comes back through the chamber, not the gas tube. On a piston gun or gas-impingement, the case is being extracted while the suppressor is still under pressure. Now you have all the pressure in that suppressor exiting both out the front and the back.

Crane: Right, but you’re saying the piston gun doesn’t solve that?
Noveske: It does not solve that. They’re both dirty.

Crane: So then how come you hear about guys saying yeah, when they’re shootin’ the direct gas impingement guns suppressed, or whatever, they’re gettin’ a lot of gas and particulate matter in their face, whereas with the piston, that it dissipates that a bit, or whatever.
Noveske: Maybe they had a different experience.

Crane: Hm. So, in other words, you’re saying that basically the piston doesn’t really offer any real advantage for that.
Noveske: What I’m saying, with a suppressor, direct-impingement and gas-piston both run dirty, and even a blowback gun or a delayed-blowback gun, like an H&K [Heckler & Koch], or any other operating system–I don’t really care what operating system you have–on an auto-loader, with a sound suppressor, they’re gonna’ all run dirty.

Crane: Right. Now, is a piston gun gonna’ put any less gas and particulate matter in your face, or are you gonna’ get the same amount?
Noveske: All a piston gun is gonna’ do different from gas impingement with a suppressor is reduce the amount that is coming through the gas tube. The piston gun is gonna’ eliminate that. I am not a scientist, but from my observations in shooting and examining the guns afterwards, it appears that the vast majority of the gas coming through is coming through the chamber. And, one example is go look at any of the HK91 or HK93-type rifles. Those have the fluted chamber and delayed blowback, and the cases are always black just like the case fired out of the gun with a suppressor. That’s because the case is extracting while it is still under pressure, and you have gas blowing back along the case as it’s blowing out, and covering it with carbon. And, that’s what’s happening with any autoloader with a suppressor. The cases all have carbon on them, because gas is escaping around the case out the chamber and into the receiver.

[DefenseReview received the following post-interview via email from John Noveske:
"Also, we should mention the poor choice of platform for the piston conversion on a round receiver bore as found on the M16/M4 system. All other piston type systems out there utilize a railed receiver design, like the M14, AK-47, M249, FAL and so on. The round receiver bore design used on the M4 is only acceptable for the standard op system. The carrier and bolt expand on axis with the bore under the normal gas impingement cycle, but on a piston gun, you run into off center impulse issues with carrier tilt and incorrectly designed carrier contact points. Some designs attempt to address the carrier tilt problem with over sized carrier tails and rollers. I do not believe the receiver extension should be used in this manor. I know many people are very happy with their piston weapons. This is not meant as a knock on the piston conversion systems out there, but as a philosophical dialogue focused the new physiological relationships applied to the M16/M4 platform through the introduction of an operating system which has traditionally been applied to receivers with rails for the bolt and/or carrier. I would rather see an entirely new weapon system designed for the piston from the ground up. I believe there several outfits currently working on this."]

While a bit dated, its still applicable today. Piston guns get dirty, just as DI, and still require maintenance and cleaning.

With that being said, since Piston guns as well as Suppressors have come a long way in the past decade, and while I was heavily biased against piston guns, because of all the common anecdotes, such as heavy, more recoil, proprietary, ect, I got board one night and saw that one of the LMT dealers had 12 inch piston kits in stock and said why not...Honestly, its REALLY good and i actually think that I may prefer it over my mid length 12 inch Spec War. I feel that it shoots a little smoother and when paired with a low back pressure silencer, its really enjoyable to shoot. Not that the SpecWar isn't, just that the piston "feels" a little nicer to shoot.

While i am not sure how good retrofit kits are, I would have no issues recommending some of the higher end stuff from LMT, LWRC, HK or even PWS.

 

[alamo5000]

While a bit dated, its still applicable today. Piston guns get dirty, just as DI, and still require maintenance and cleaning.

With that being said, since Piston guns as well as Suppressors have come a long way in the past decade, and while I was heavily biased against piston guns, because of all the common anecdotes, such as heavy, more recoil, proprietary, ect, I got board one night and saw that one of the LMT dealers had 12 inch piston kits in stock and said why not...Honestly, its REALLY good and i actually think that I may prefer it over my mid length 12 inch Spec War. I feel that it shoots a little smoother and when paired with a low back pressure silencer, its really enjoyable to shoot. Not that the SpecWar isn't, just that the piston "feels" a little nicer to shoot.

While i am not sure how good retrofit kits are, I would have no issues recommending some of the higher end stuff from LMT, LWRC, HK or even PWS.

If you read carefully, the thing he says is that the primary 'reason' people use to justify going to a piston system is the idea that they are 'cleaner'. Simply put that by itself is not true.

"Clean" is much more a function of ammo (in my opinion) than it is operating system. The caliber, the suppressor, and the powder type have much more impact on being 'clean' and/or not getting gassy face.

The other thing he points out is that retro-fitting a piston into a system that wasn't designed for a piston can cause other more mechanical issues.

Yes things have come a long way. There have been things done to supposedly address some of those problems. He said it's not a knock on pistons systems as a whole. Some guns are excellent with them, but his point was trying to put those systems on a gun that never was designed for them can induce other problems. At the time none of the details of those problems had viable solutions in the AR market space. His point though is that [to him] retro fitting a DI gun in a standard AR design makes little sense, especially since the whole 'being cleaner' thing isn't exactly totally true. Yeah there will be differences, but in both instances it's still dirty, especially considering and depending on the other components [suppressor, ammo, etc].

Still though, piston systems (when talking specifically about ARs) will introduce proprietary parts. With that in mind, choose wisely. Picking from the upper echelon of choices would definitely be smart. Those companies are going to be around to fix things if something should break.

To me, now a days, a much better solution to those wanting less gas in the face is to just go for the flow through suppressor designs. That's a substantially better option than trying to re-design parts of the AR system.

Edit:
I will also add that had John Noveske not pointed all of this stuff out, the odds are that some of the later 'developments' to components [IE anti carrier tilt, etc] would probably not have gotten the attention they needed. Not saying they wouldn't have developed those things eventually, but his pointing out this stuff pushed those in the game to go ahead and do it. In other words he definitely had a huge impact on the AR world for 100% certain.

 

[Milf Dots]

It's reasonable to say that if Stoner & his colleagues had designed the piston AR18/180 before and not after they came up with the Di version, virtually no one would be defending or promoting direct impingement.

The best AR piston systems DO run cleaner than Di because a noticeably smaller percentage of fouling and heat make their way into the critical plumbing.

If a piston gun's piston system fails, very often the rifle can be fired as a single shot firearm. If a gas tube fails, the rifle is often incapable of firing.

Buy and shoot what you like!

 

[TheHorta]

Just my $0.02 in a world where pennies are worthless…

I own multiple piston guns — Adams, HK, PWS, LMT, SCAR, etc.

Not ONE of them runs any cleaner than any of the DI guns I own — KAC, LMT, Geissele, etc — using the same suppressor. My TBAC cans and my Dead Air Nomad LT Ti are all high-backpressure cans and are filth-generators. For all practical purposes, the fouling is identical between all guns — DI or Piston.

The one HUGE difference is when using my OSS/HUX “Flow” low/no-backpressure cans. Those things are as close as you can get to shooting unsuppressed, when it comes to chamber fouling. The added benefit is not having to worry about the gas system… at all! The gun has no idea a can has been added and it behaves just like it does unsuppressed.

In short, Noveske is 100% dead-on. A piston gun simply won’t keep your chamber appreciably cleaner, but a zero-backpressure can sure as hell will. Running a typical can with standard backpressure will fill your face with the same noxious gasses regardless of your type of gas system. 95% of the volume is coming back through the chamber, not the gas system.

While there MAY be a SLIGHT decrease in returned gasses, it’s so nominal as to be basically irrelevant to any practical degree.

 

[Milf Dots]

One of the things I love about my Sig 516 vs my Di gun is that the piston gun goes much longer without needing cleaning, and when I do clean it, it just needs a quick wipe down. Put simply, the amount of cleaning, and WHAT and HOW the cleaning needs to be done, are in my mind one of the great benefits of piston systems. YMMV

 

[jLorenzo]

Either way, I still want one. Not dogging DI guns at all. I have them and like them. Just going to try a piston because I don't have one.

 

[TonyTheTiger]

If a piston gun's piston system fails, very often the rifle can be fired as a single shot firearm. If a gas tube fails, the rifle is often incapable of firing.

Explain please.

 

[Hoody2shoes]

I gotta be honest, I don't really listen to the 'proprietary' crowd when most of them are running KAC or LMT's that use proprietary gas lengths, bolts, and other parts that require dedicated tools to work on.

 

[supercorndogs]

My Adam's arms kit gun always had a very loud pop from the ejection port whe. Shooting suppressed. It was quite a bit louder than my other guns. It left brass black as a piece of coal. About the only way I could see to adjust the timing was to move the block u til max clearance was achieved where the drive rod met the gas block. It didn't help. It was at least as dirty as any DI gun, and not smooth at all for a rifle length gas system. I always figured the timing was different since the gas was working at the gas block instead of having to fill the tube and travel to the carrier.

 

[Flyingbullseye]

Used SA on two upper builds, never had any issue with either. I looked at AA before making my decision and while I've never used one everything I read was that Superlative arms is supposed to be a better system.

Kind of hate doing this be OP if you haven't purchased a kit yet I'm selling a mid length SA piston kit in the post exchange.

 

[Holliday]

Crane: You’re not doin’ a piston gun, right?
Noveske: No.

Crane: Do you have any plans to do a piston gun?
Noveske: We have piston plans, but we don’t have any plans of putting it in production, because it’s…I don’t think it’s necessary. I’ve got piston guns here from other makers, and they’re dirty, and I don’t see…

Crane: Whadya’ mean "dirty"?
Noveske: Open up the bolt and look inside, and it’s dirty inside. The whole thing about them running clean is not necessarily…o.k., let me back up. I only run the guns with suppressors for testing when I did my comparison, and with suppressors, direct-impingement and piston-operated were both very dirty, ’cause the blowback comes to the chamber, not the gas tube. And, I’m not real happy with the piston systems that I’ve shot and examined, so it’s just to me, it’s not…

Crane: Well, the piston…the advantage for a piston with a suppressor on there is supposedly it doesn’t blow all the gunk back in your face.
Noveske: O.k., but what you’re not paying attention to is that all that crap comes back through the chamber, not the gas tube. On a piston gun or gas-impingement, the case is being extracted while the suppressor is still under pressure. Now you have all the pressure in that suppressor exiting both out the front and the back.

Crane: Right, but you’re saying the piston gun doesn’t solve that?
Noveske: It does not solve that. They’re both dirty.

Crane: So then how come you hear about guys saying yeah, when they’re shootin’ the direct gas impingement guns suppressed, or whatever, they’re gettin’ a lot of gas and particulate matter in their face, whereas with the piston, that it dissipates that a bit, or whatever.
Noveske: Maybe they had a different experience.

Crane: Hm. So, in other words, you’re saying that basically the piston doesn’t really offer any real advantage for that.
Noveske: What I’m saying, with a suppressor, direct-impingement and gas-piston both run dirty, and even a blowback gun or a delayed-blowback gun, like an H&K [Heckler & Koch], or any other operating system–I don’t really care what operating system you have–on an auto-loader, with a sound suppressor, they’re gonna’ all run dirty.

Crane: Right. Now, is a piston gun gonna’ put any less gas and particulate matter in your face, or are you gonna’ get the same amount?
Noveske: All a piston gun is gonna’ do different from gas impingement with a suppressor is reduce the amount that is coming through the gas tube. The piston gun is gonna’ eliminate that. I am not a scientist, but from my observations in shooting and examining the guns afterwards, it appears that the vast majority of the gas coming through is coming through the chamber. And, one example is go look at any of the HK91 or HK93-type rifles. Those have the fluted chamber and delayed blowback, and the cases are always black just like the case fired out of the gun with a suppressor. That’s because the case is extracting while it is still under pressure, and you have gas blowing back along the case as it’s blowing out, and covering it with carbon. And, that’s what’s happening with any autoloader with a suppressor. The cases all have carbon on them, because gas is escaping around the case out the chamber and into the receiver.

[DefenseReview received the following post-interview via email from John Noveske:
"Also, we should mention the poor choice of platform for the piston conversion on a round receiver bore as found on the M16/M4 system. All other piston type systems out there utilize a railed receiver design, like the M14, AK-47, M249, FAL and so on. The round receiver bore design used on the M4 is only acceptable for the standard op system. The carrier and bolt expand on axis with the bore under the normal gas impingement cycle, but on a piston gun, you run into off center impulse issues with carrier tilt and incorrectly designed carrier contact points. Some designs attempt to address the carrier tilt problem with over sized carrier tails and rollers. I do not believe the receiver extension should be used in this manor. I know many people are very happy with their piston weapons. This is not meant as a knock on the piston conversion systems out there, but as a philosophical dialogue focused the new physiological relationships applied to the M16/M4 platform through the introduction of an operating system which has traditionally been applied to receivers with rails for the bolt and/or carrier. I would rather see an entirely new weapon system designed for the piston from the ground up. I believe there several outfits currently working on this."]

Interesting perspective. Thanks for posting that.

 

[GUNNER10]

Just my $0.02 in a world where pennies are worthless…

I own multiple piston guns — Adams, HK, PWS, LMT, SCAR, etc.

Not ONE of them runs any cleaner than any of the DI guns I own — KAC, LMT, Geissele, etc — using the same suppressor. My TBAC cans and my Dead Air Nomad LT Ti are all high-backpressure cans and are filth-generators. For all practical purposes, the fouling is identical between all guns — DI or Piston.

The one HUGE difference is when using my OSS/HUX “Flow” low/no-backpressure cans. Those things are as close as you can get to shooting unsuppressed, when it comes to chamber fouling. The added benefit is not having to worry about the gas system… at all! The gun has no idea a can has been added and it behaves just like it does unsuppressed.

In short, Noveske is 100% dead-on. A piston gun simply won’t keep your chamber appreciably cleaner, but a zero-backpressure can sure as hell will. Running a typical can with standard backpressure will fill your face with the same noxious gasses regardless of your type of gas system. 95% of the volume is coming back through the chamber, not the gas system.

While there MAY be a SLIGHT decrease in returned gasses, it’s so nominal as to be basically irrelevant to any practical degree.

I think part of the reason that I like my 12 inch LMT piston so much is that its paired with a very low-pressure Sandman K. Still gets dirty but is just so pleasant to shoot, but that really applies to any rifle with a low pressure can.