I have been looking at a gas piston ar.  Are they really worth the extra price?  What are the pros and cons of them, what is the purpose of a gas system.  Sorry, it's probably a dumb question, but im a newbie.

And we're off...

I don't understand the piston craze.

I also don't understand the people who jealously defend them.

Gas tubes do exactly what they are supposed to, and they cost $10.

I will never, ever consider a piston unless I build a suppressed SBR. Which will never happen.

ETA: READ THIS THREAD if you want to understand how direct impingement works.

I see no reason for one, myself and would like to know(like the op) .......what is to be gained by installing one?

I have a good friend, that has been buying and selling AR's for over 30 years. He also see's no need for one either.

I own DI AR's and a Piston AR.  ALL my AR's work fine for what I use them.

Other than ease of cleaning, it's unlikely any of us would realize any real benefit from using a piston AR.

Piston on AR's shine in SBR, Suppressed and Full Auto applications. Their use for semi-auto guns in less strenuous applications is debatable.

Are they WORTH the extra price?  Only you can answer that.  If you do one of the above, maybe.

If you're just curious... maybe.  I'll be honest and say I got mine because I was curious, and the overall quality of teh rifle and components are excellent.  But for now, my Colt 6920 is my go-to gun.

Where they shine is the SBR's, full autos, and guns you run suppressed. Seeing as I do all three, its worth it to me. I wouldn't get a piston in a barrel longer then 11.5", or for a gun I didn't plan to use a can on. You really loose the benfits of the piston on them.

gas piston system does run cleaner. With current $400+ price tag, you may well buy a true gas piston rifle like an AK.

Gas impingement has been running well for over 40+ years. If it had not worked, it would have been replaced with other systems already.

The DI gas system is a great system, but it is not optimal for the short Carbine set up (16" barrel ength and shorter).




As much as the M4 Carbine is really liked and well used, it is more prone to carbon fouling due to the short Carbine gas system, which increases the chances of jams or bolt carrier seizure, which makes it much more maintenance intensive.



The growing popularity with Piston Driven AR's or Gas Piston Uppers (especially in Carbine applications) is that they are not maintenance intensive compared to the DI Gas System since the Piston Systems eliminates the Carbon Fouling and Heat related issues in the upper receiver, and the bolt carrier group.



This reduces or virtually elimates the chances of Jams or Bolt Carrier Seizure during operation, due to any sort of Carbon Fouling, since the bolt and upper receiver are kept clean and cool..

A 16" with a midlength gas system eliminates all the problems with carbine length gas systems. There is no need for a piston set up if you can get a middy on a 16" barrel.

I've mentioned this before,  but Reed Knight doesn't even believe that gas piston systems are right for the AR platform, and you probably know that Mr. Knight had

a bit more than a passing acquaintance with Eugene Stoner, inventor of the AR system.  






Upon careful evaluation,  it's apparent that gas piston systems are wrong for the AR platform.    Examine the functional dynamics of how the bolt system operates

in the direct impingement system.    The gases are directed through the gas tube, through the snorkel, into the chamber BEHIND the bolt in the bolt carrier, and gas pressure forces

the bolt FORWARD, ensuring that it remains fully closed and in battery, while at the same time starting the carrier on its rearward journey.  



With a gas piston system, there is no gas-assisted pressure on the bolt to keep it in battery while chamber pressures taper off.



Also, with the direct impingement system,  the action of the gas pressure on the bolt and carrier is straightline axial force.   The bolt and carrier are not

subject to bending, twisting or torqueing forces and neither is the upper receiver.



With a gas piston system, the off-axis thrust of the piston on the top section of the carrier results in heavy downward pressure on the rear bearing surfaces

of the bolt carrier, and hence faster wear on them,  plus on the contacting surfaces of the upper receiver.   The entire carrier system is being forced

downward at the rear in a bending movement.    This is hardly optimal.





Gas piston sytems for ARs look like a good idea until you stop and analyze how the system on an AR actually operates.





CJ

For those of us who are driven to keep our weapons well oiled and spotless, and still like to shoot, a piston gun is well worth it IMO. Hours of cleaning saved. Don't know about the off axis thing on a AR15, but the Sig556 works just fine imo. Then again it was designed as a piston gun from it's inception and has a 55x upper.

Since everyone else here is giving their own 'OPINION', there's mine!!!  I actually have one...........LMT MRP CQB Piston.  I don't have carrier tilt!!!  I don't have unusual wear anywhere I can see!!!!   It runs well and is more accurate than I am!!!  It is definitely easy to clean and doesn't require that 'wet' look!!!!!

Anyone else that has one can speak up now!!!  All the rest can keep blowing hot air (gases just like in your own DI version) for experience!!!

Do you also own a DI AR?

Dont even bother with a conversion.
Any manufacturer who relies on selling conversions is going to be broke in a few years.  The owners of their conversions terrible idea will be stuck with a rhino.

If you want to hear a GP conversion failure story, call me on a friday night and be prepared to hear a man rant for 30 minutes.
The mfg did return my $, andlet me keep the crappy POS parts which i sold instead of tossing into the Atlantic Ocean. I literally considered driving to the Atlantic Ocean and doing it.

People who are overly concerned about how clean their rifle is should avoid joining the military.  That obsessive/compulsive disorder

will get you killed in the sandbox.    Your rifle is a tool.  All tools are meant to get a little dirty.  Shoot it, have fun, and don't worry

about a little dirt in it.  Save the cleaning for when you get home, after dinner.     The cleanliness issue is a bogus argument for

the gas piston.   It's right up there with the guy who spends 25,000 dollars dressing up his 4x4 and you ask him, "So how does

it do in the mud?" and his answer is "

...M...m...m...m....MUD????

"     Kinda silly when you stop and think about it.



If you have a gas piston upper, you DO have carrier tilt, PERIOD. Off-axis thrust guarantees it, by simple physics.

That WILL result in accelerated wear in the rear of the upper's bore and on the bearing surfaces on the bottom

of the carrier.   Plus you're possibly in danger of experiencing problems associated with shell extraction while chamber

pressures are still high,  as a gas piston system doesn't hold the bolt in battery for that extra millisecond.



A gas piston system is not an improvement on the AR15 action.  It introduces more potential problems than it solves.



It's a solution to a problem that doesn't exist.





CJ

Hours of cleaning? You do realize that piston guns get dirty too, right? I don't care if my rifle is spotless. I care if it goes bang every time I pull the trigger. So far, direct impingement has never failed me.

I've gone HUNDREDS of rounds before cleaning, and I know guys who have taken carbine classes and gone a couple of thousand rounds, while doing little more than oiling up the carrier.

CJ,

You do know the difference between fact and theory don't you.......Facts are PROVEN and theory is just SPECULATION due to arithmetic, physics, etc...  Kinda like the good ol' evolution theory..........people all the time think that just because it seems right on paper, it's right.  However, when 'TESTED', good ol' evolution theory doesn't hold water!!!

So I have to ask if you have personally tested or owned a piston AR???  I have and I can tell you by OBSERVATION that I don't have carrier tilt!!!  

I really don't care that you can show me the axial rotation of the bolt by the operating rod theoretically induces tilt/wear..........In REAL LIFE, mine does not show wear!!!  LMT spent over 2 years of research and development, tens of thousands of rounds, and countless thousands of dollars in REAL TESTING!!!!!!!  Where's your REAL TESTING????  Any more is just what I stated in my last post............HOT GASES SPEWING FORTH FROM AN ORIFACE!!!

Its hard to take you seriously after reading this...

I understand cb.....It was just hard to take CJ seriously when it seems that he doesn't have anything other than opinion.  I come from a very analytical background and testing is what determines real world conclusions for me.  I can look at things all day long and say, it should happen that way, but in testing, the results speak for themselves.  I'm not saying I have 'tested/owned' any other brands.  I am saying I have an LMT MRP CQB Piston 16" and I've yet had any issues with it.  

I too can understand where and how people jump to conclusions.  I am also aware of others here that have tried different 'piston kit retrofits' on their ARs and have had very bad results.  It's just that there are others here also that have purchased LMTs, LWRCIs, POFs, and Barretts without having any issues.  This whole piston vs di argument has gone on way too long and it's tiring to the nth.  I am getting a little tired of the rhetoric being parroted here from hearsay, mirrored just to hear yourself talk.  New guys come on here all the time looking for sound advice.  I give them my experience and I'm lumped in with the 'Piston' crowd.  These are all AR's to begin with.......not military M4s or M16s for goodness sake.  I would be willing to wager that for the vast majority of people here, they use their rifle as a fun thing to shoot on weekends, or to impress others with their EBR.  I, like everyone here was new once and asked a lot of questions.  It's up to the people with experience to give their experiences.  If you want to give your opinion, then say so......nothing wrong with opinions other than they are just that....opinions/thoughts/hearsay.

I asked a simple question to CJ......Does he or has he ever owned a piston operated AR???  It's not a hard one, but just like politicians, some people don't usually like to have the spotlight shown directly at them.  

And for the answer to the other persons question........no, I don't own a DI version of the AR.  I have shot them, taken them apart, cleaned them, and enjoyed them.  I wanted and waited 8 months for my Piston LMT.  The very day I placed my order/got put on the waiting list, I could have purchased the exact same model LMT except it was their DI version.  I chose to wait and I chose to spend my money the way I wanted to.  Thank God I live in a free America!!!

Now if it's for the 'evolution' comment..........well, all I can say is please do your due diligence before making up your mind.

Nothing is ever proven in the scientific world my friend. There are only disproven or confirmed hypothesis's.  You can only prove a hypothesis false, but you can never prove it, only confirm it.  The more you confirm it, the higher probability you have of finding the  truth about the situation.  Water freezes at 32 degrees F; not a fact, just a confirmed hypothesis. Though its been confirmed enough that we just call it fact in the normal world.

In regards to the piston system,  I think its the way to go.  I've never shot a piston AR, but I do know that every application that was tested for the replacement of the m16/m4 was a gas system.  All the new guns are gas systems, for a reason.  I'm sure that reliability and dependability issues have come up, but the Gas system to me obviously has the upper hand.  Every new rifle issued to the military today is a gas gun, go figure.  The Knights Armament m110, FN SCAR, H&K 416, Bushamster ACR, all gas guns. Though I could be wrong about the m110.

The guys at KAC don't. In fact, they think a short-stroke piston on any M4/M16 is a bad idea.

That's probably why the SR-15/16/25 all come with gas tubes.

I believe pistons have their niche. But putting a piston on a 16" unsuppressed upper on a semi-auto only lower makes no sense to me, at all.

I was Infantry for 8 years, I can tell you there is a difference between battlefield cleaning and in garrison cleaning.
There is still no excuse for putting away your weapon dirty, that is just plain lazy.

In regards to KAC, I don't have any knowledge on the matter, so I could be wrong and you could be totally right... well put.

No, I don't own a gas piston AR nor do I intend to do so.  



As for the carrier tilt issue,  it can't actually tilt if it doesn't have the clearance to do so, but the force that

would induce that tilt, if room were available, is still there.  If you were to place force sensors on two

ARs that started out identical but one was converted to a gas piston system, you WOULD be able to

measure the downward force borne on the rear of the lower receiver, and the carrier.  It is certainly

quite a bit more than on the direct gas system example.



I don't have any interest in putting things on my rifle that will cause faster wear on anything.



You're still ignoring the difference in how the bolt is held in place by gas pressure with the direct gas

system, vs. not at all in the piston system.  This is potentially an issue of much greater importance

as nobody should feel comfortable firing a 60,000 CUP pressure rifle cartridge with what is essentially

an unsupported bolt!





I formulated my opinion following the highly educated opinion of C. Reed Knight.  There is no greater living

authority on the AR-15/M16 platform.   If you disagree, go argue with him.  You'll lose badly.





CJ

Well, to be fair, Mr Knight has a motive here.... he sells Stoner Rifles.  I doubt you'll ever see an SR-XX with a piston on it.

OTOH< I don;t think there's anything wrong with the DI system, per se.




That's true... but so what?  You might expect to see reduced accuracy from a piston system because of this... but we don't.  You might expect to see more wear on the bolt lugs.  But again, we don't.  I  am unaware of any problems of Piston AR's coming out of battery too soon.  And I suspect the lower operating temperature of the bolt probably offsets the increased friction during the unlock.



Again true...  but so what?   Such things matter ONLY if they contribute a failure mode.  I'm not aware of any problems caused by this.  Most of the problems I've heard of with Piston AR's are related the usual engineering bugs you see in a new product... it's a matter of working out the problems.






And yet, they seem to do just fine.  Do I think DI AR owners need to scrap 'em and get a Piston AR?  No.  But there is nothing wrong with pistons on an AR either.

Yeah.. it couldn't POSSIBLY be because Gene Stoner worked for them! ;)

If I were to argue theory with Mr. Knight, I would no doubt lose.  The man is a skilled engineer.  But I am an engineer too.  And I'd ask him to present data.... evidence if you will, that his theories are realized in actual practice.  I don't experience extraction problems with my Piston AR.  And as far as I know, no failure in a Piston AR has been related to receiver wear.

Thanks for the post Strongbow, but I think you are talking with my 15 year old hard headed son that refuses to take off the blinders.  

No one here says you should throw away your DI rifles.  I agree that the DI system works.  For all general purposes, it works........it FLAT OUT WORKS!!!!!!!!!!!!!  

However, I happen to like my LMT Piston, I have no issues with it, I can change back to DI with just a barrel/BCG swap, I can change calibers just as easily.  It shoots softer than my neighbors S&W M&P 15 and is more than accurate enough for me.  To clean it, I just disassemble it and wipe it down and add a drop of lube here and there.  No cleaning hard, built up carbon off the bolt.  I don't care if you with your DI rifles don't clean off your bolts or whatever with YOUR rifles.  I'm not telling you to throw them away.  I'm just telling you and the OP my experiences with MY rifle.  I happen to like it.  My gun dealer/gunsmith that sold me the LMT Piston said all the same things you guys are saying..............."why do you want/need a piston AR???"  

I told him the same thing I'm telling you guys....it's my money, LMT makes a Piston AR, it makes ME happy, LMT spent years/lots of money/thousands of rounds developing this rifle platform, I have no problems/issues with it............BTW, have I mentioned that it makes ME HAPPY!!!!!!!!!!!!!!!!

And with that, if the OP wants to ask me any specifics about my LMT MRP CQB Piston rifle, please feel free to PM me here.

Take care all;


One other thing to the person about proving verses facts.  Semantics and from my favorite web encyclopedia Wikipedia:

"In mathematics, a proof is a convincing demonstration (within the accepted standards of the field) that some mathematical statement is necessarily true. Proofs are obtained from deductive reasoning, rather than from inductive or empirical arguments. That is, a proof must demonstrate that a statement is true in all cases, without a single exception. An unproved proposition that is believed to be true is known as a conjecture.

The statement that is proved is often called a theorem. Once a theorem is proved, it can be used as the basis to prove further statements. A theorem may also be referred to as a lemma, especially if it is intended for use as a stepping stone in the proof of another theorem.

Proofs employ logic but usually include some amount of natural language which usually admits some ambiguity. In fact, the vast majority of proofs in written mathematics can be considered as applications of rigorous informal logic. Purely formal proofs, written in symbolic language instead of natural language, are considered in proof theory. The distinction between formal and informal proofs has led to much examination of current and historical mathematical practice, quasi-empiricism in mathematics, and so-called folk mathematics (in both senses of that term). The philosophy of mathematics is concerned with the role of language and logic in proofs, and mathematics as a language."

I guess we agree.........However in our universe, some things are and have been proven.  Over and over again, and again, and again forever as long as we are human.  We don't evolve intellectually, haven't since the beginning of time and as far as I see it, won't!!!  The only progress of mankind has been in technology..........but this isn't the old all nighters sitting in the dorm room smokin' and drinkin'.....This is ARfcom and as such should be discussing ARs and their design.

LOL well put.  keep it on topic.  It may be a waist of time to discuss philosophy, mathematics and proofs, by using syntactic formal logic and confirmed hypothesis's etc.  Um... AR15s rock!

I have gone thousands of rounds before cleaning... Just run a bore snake though my piston uppers and that is about it.








 

That is their opinion, and other opinions and people's experiences differ from theirs.








 

That is a fair summary Strongbow





 

Here's an email my buddy Tom sent me:



Here's my reply:



Piston ARs have been around almost as long as ARs have.  Colt did one in the '60s, Singapore did one, the Rhino, etc. etc.

John Noveske doesn't care much for the piston either. From an interview with David Crane of DenfenseReview:  

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."]

I don't think gas piston systems are ordinarily going to be problematic unless you get into very high round counts and the upper receiver wear issue actually BECOMES an issue,

but that probably takes well over 10,000 rounds to get to that point.  The hard anodized upper receiver bore is very tough and will last a long time, BUT, once you wear

through the anodize, additional wear will occur at a greatly faster rate as parkerized steel > raw aluminum,  lubricated or not.





I don't OBJECT to gas piston systems, I simply don't see any NEED for them.   I didn't before, and I sure don't now.   I see them as a way to spend money you didn't

have to spend to solve a problem that doesn't exist, and introduces its own idiosyncracies that may or may not ever have to be addressed at some point as a cause of

a problem that wouldn't have existed with the stock DI system.





CJ

Weaknesses in the DI that are pretty evident especially with the
introduction of the Carbine set up, which is not the optimal set up or
length for the DI gas system.  





The DI gas system is more maintenance intensive vs. a piston driven system, which does not require the same amount of maintenance, attention, cleaning and lubrication as a DI Gas system does.





The AR is a modular weapons platform that can be adopted
to different uses and applications, and the introduction of Well
Designed, and Quality AR Piston Systems is a very excellent use of the AR's design flexibility.
I have put my personal GPU test rigs through all kinds of torture tests, to the point of wearing out the
barrels at around 15,000- 20,000 rounds, and the piston systems in each of the test
rigs are still running strong, without any issues or parts breakages.  
I have been able to shoot 3000+ rounds without so much as having to
touch the piston system for any sort of maintenance, cleaning or lubrication.  All I did was was bore
snake the bore and chamber and wipe the bolt face off.  





Ultimately there are different types of users and applications for
both the DI and Piston Driven AR's, and it is up to the individual user
to see which one is more beneficial for them.

Again... what's the anticipated failure?  Any evidence they have occured?  There are psiton guns will well over 10,000 rounds through them and I've never heard of a failure related to receiver wear.




I'm not sure you NEED one, but there are those who claim teh AR platform is unsuitable for pistons. I thought you were earlier.  I'm just sayin' "back it up."  I have both DI AR's and a piston AR.  All of 'em work fine.  My "got to" atm is a DI gun (a Colt), but the piston has been flawless so far.... and much easier to clean.



Fortunately, it's not your money we're spending. :)  Some high-end DI AR's are more expensive than good quality piston AR's (KAC SR- series rifles as an example)



And removes other idiosyncrasies.... such as heat build up and fouling in the receiver.  The conversion of the AR-15 system from a rifle-length gas system to a carbine length gas-system introduced.  Also, piston AR's tend to be less finicky about ammo and less likely to suffer from problems related to gas leaks (fewer places for gas to leak from).

I'll repeat:  There is no fundamental engineering reason a piston won't work on the AR platform.  And many successful rifles demonstrate that.



[/quote]

But, just because it works, does that mean that it has to be done that way?   Of course not.





My opinion and position is based on the insights and evaluations of Messrs Stoner, Knight, and now, Noveske, in addition to my own analytical look

at how the system operates.  I have definite reason to believe that Mark LaRue would tend to agree with all of the above as well.





Let's see...possible, and (sometimes) observed "issues" with GP systems in the AR platform that have been mentioned so far:  Bolt breakage.

Faster wear of the upper receiver bore.  No cleanliness advantage when firing suppressed.





I'm already past the point of being interested.






The GP system solves...what, exactly?   Enhanced reliability?  No evidence of that when comparing to a modern rifle built by someone who

knows what he's doing.   No accuracy improvement...or loss.    So it's a little cleaner in the carrier section of the receiver in non-suppressed fire.

I'm unable to think that's a big deal, certainly not enough of one to want to spend at least a few hundred extra dollars for it.



Cost/benefit analysis results:  Not worth it to me.   Furthermore, I believe than anyone who's all excited about this "next greatest thing" gas piston

kit should be aware of the opinions cited in this and other related topics,  the opinions coming from the industry's most experienced designers

working in the AR platform.   None of which are particularly supportive of the gas piston system idea.





The gas piston system is different, and certainly it's workable, but I just don't think that any rational analysis of it can declare it to be superior

to the regular DI system.  Why spend money on something different if it's not better?    I don't see the logic in that.




CJ

I work directly with operators in the field, from Military to Law Enforcement, and the opinions of the folks I work with, will greatly differ from yours or from some of the top industry designers.
 

Whoever said it HAS to be done?  I think it's a viable option, not a necessity.



Fine, but I ask you the same questions I would ask them.... where's the data?  I mean, I respect their positions, but it's one thing to say "Yeah, pistons on an AR are a bad idea" it's another thing to show the data.  That's all I'm saying.




What sort of bolt breakage are you talking about?  I have seen no evidence that bolts break on Piston AR's any more than on DI AR's.  You do know bolts break on DI AR's right?



Again... so?  What sort of failure does that cause?  



I'm not sure I'd call that an issue... but in any case, even as indicated int eh snippet posted, MANY suppressed users report rather different experiences.



Welp, no one's making you read and post in the thread... you must still be interested, or you wouldn't waste your time, right?



I don;t disagree with that.  At this point there is no evidence piston AR's are more reliable than their DI cousins. That's not to say there aren't, but no one has done any sort of credible test I'm aware of (I'm not counting the "dusting" test)


I'm unable to think that's a big deal, certainly not enough of one to want to spend at least a few hundred extra dollars for it.



to YOU, and that's the point.  No one is making you buy one. That doesn't mean they're not worth it to those who do decide to buy them



Certainly LMT seems to think they're worth building.  And LWRCi.  And a number of others.  So far, my LWRC hasn't exploded and has gone bang every time I pull the trigger.  And there's lotsa of other happy buyers too. They must be doing SOMETHING right.



Why buy an EOTech over an Aimpoint?  Why buy an LMT instead of a Colt?  Why buy a Ferrari instead of a Maserati?  Not everyone will agree with your analysis.  And sometimes people buy something just BECAUSE it's different.  It's a hobby for most of us after all.  Though there are certainly plenty of real world operators who use Piston AR's.



I'm not sure logic is your strong suit. ;) (I'm pulling your leg there)





[/quote]

Look, the fact is that it's better not to have hot, dirty gas blown back into your reciever.  That's why the AK, FAL, and just about all other autoloading rifles use a piston system.

Now maybe the AR's system doesn't cause problems most of the time, or even almost any of the time unless you're dumping 30 round mags out full out from a short gas system.  But it's still not as good of a design as a piston.

As piston systems become more common and priced the same as a DI system, you'll see fewer and fewer DI's sold.  There will still be people saying "It's a soultion looking for a problem", similar to 1911 folks about DA semis.  To each his own.

I have 2 POF'S and love and them but I have 5 DI guns and love them to (can't we all just get along ) good read though !

I have to agree. I have 1 LMT piston a 1 Noveske, so I figure I have the best of both worlds.

Piston systems for the AR have been around since the Armalite company started prototyping for what became the AR platform.

If it wasn't good enough then and no one has made a good enough piston op AR since then that replaced the DI then it's probably not going to happen.

I refer you to the 1970's era retrofit system I posted on the first page.

Pistons are fine on SBR and suppressed AR's, anything else is a waste of $$.

Personally I'll just take my $300-$600 for a piston system "upgrade" and have the BCG, barrel extension, and FGC coated in Diamond Black and have my upper hard anodized with Teflon for my DI guns.

Maybe I'm new here, but every time I see one of these DI vs Piston threads, I always wonder why people don't link to the Army's own testing of the Colt M4 against the HK XM8 / HK 416 / FN SCAR (3 piston rifles).  Has this testing been debunked and nobody ever talks about it anymore?  Did I miss that thread?

http://www.armytimes.com/news/2007/12/army_carbine_dusttest_071217/

OK so first things first:  the XM8 and SCAR are thrown out because they are not AR's, but the HK 416 is pretty much the same as all the other piston AR upper receivers out there.

The Colt M4 had almost 4 times as many failures as the HK 416 in a 60000 round test (882 vs 233).  DI vs GP is the main difference between the Colt M4 and the HK 416, right?  That seems like pretty conclusive proof that GP > DI in terms of AR-platform reliability.

Just to put it into a simpler perspective, 60000 rounds is 2000 magazines.  882 failures (Colt M4) is 1 failure per 2.26 magazines.  233 failures (HK 416) is 1 failure per 8.58 magazines.

Does a gas piston automatically make an AR significantly more expensive?  Maybe someone here with a knowledge of manufacturing could figure out what the actual increased cost in design and materials is over the DI design.  I would agree that the GP rifles are more expensive right now, but argue that has less to do with increased design and materials costs and more to do with the limited production numbers compared to DI AR's.  If the price were the same, would you buy the cleaner design?  What's the price difference where you start to consider the cleaner design?

So the last leg to stand on really is the carrier tilt issue, which is not a myth, but right now seems to be unquantifiable (or at least not tested as well as the reliability testing above).  If you own a GP AR, carrier tilt might happen, you might see the increased wear on your rifle, and one day it might impact the operation of your rifle.  But nobody can say conclusively (a) when the problem occurs and (b) what happens to the gun's reliability because of it.

Anyone who speaks in absolutes is suspect. "The piston system is the best." Or "DI works best". Typically shows they have some kind of emotional or financial investment in the system of which they speak and would take such statements with a [large] grain of salt. Simply put, one system is not better than the other. Basically all you are doing is changing one set pros and cons for another.

The perfect system does not exist. Everything in life is a compromise. Going from piston to DI or DI to piston just means you are give up something to gain something else.

It has been well established that the dust tests may have been biased.

The "piston" guns tested were guns that the manufactures were allowed to prep before the testing.

The M4's were pulled from inventory.

Repeat testing also resulted in the M4's having less than half the number of failures vs the original testing.



If I want a piston operated gun I'll buy one designed from the ground up to use a piston.

Not a piston shoehorned into a rifle that wasn't designed that way that may or may not have problems later in its life cycle.


Also google "problems with HK416" it will be educational.

I think "well established" is overselling the point a bit but I agree that the test had some problems.  I am curious about your last statements.  Can you point me to the results of repeat testing?  I'm not saying it didn;t happen, it's just heresay until I can see the data myself.





That's up to you, but there are advantages to using the AR platform fro those that want a piston gun: parts commonality and platform training.  My LWRC is 80%+ common with my Colt.  If a part breaks, I can get a replacement from almost anyone unless it's one of the proprietary components.  On a platform like the SIG, or XCR, or SCAR, if something breaks, there's only ONE source for parts.  AS for training, it's transparent to me as a user between my DI Colt and Piston LWRC.  I can train with either and be training for both.  Not so with another platform



AS I've demonstrated, from an engineering point of view, that's a bogus argument unless you back it up by data, and you can't.  You might as well say you should use a gun designed as a carbine from  the ground up instead of a rifle-length system kluged up to operate as a carbine. There were engineering problem s associated with this transition.They were overcome until satisfactory performance was achieved.  But it is a FACT that the carbine gas system is harsher on the gun than a rifle-length system.... parts wear out faster.  I don't see the same argument from your side suggesting we dump the M4 for a dedicated carbine design..... because it's a nonsense argument.




Another BS point.  Google "problems with M4 carbine" and see.  Any machine made by man will have failures.  But you need consistent data.  Internet posts don't constitute engineering data.

Which is what I thought the point of the HK 416 was:  as a drop-in upper receiver replacement that could use the same lower receivers, magazines, optics, and had the same control setup as the Colt M4.  The training / parts impact is minimized (compared to a total replacement) for a significant (measured) increase in reliability.



The main thing I could find was problems in Norway related to cold weather (a problem their Colt issued weapons have too) and the selector for firing suppressed / unsuppressed.  What's the point of a suppressor on a supersonic round?  Apparently these weren't big enough issues to impact the dust testing posted above.  Please understand, I'm not saying that the HK 416 is the Jesus Rifle that is perfect in every way, my point was only to refute what CJ says above, that nobody has proven better reliability with a piston AR.  The US Army showed that the HK 416 is more reliable, which is about as close to a piston AR as any of us are buying out here.

Do you have an AKO/DKO password?

If not then your not going to be able to look at the reports yourself.

I'd post a copy paste of the tests but it's 240 pages long and I don't have an entire day to make a short version for you as I'm currently in Iraq.

You didn't think the dust test was the only test in that evaluation did you?  Army Times printed the dust test due to it's "sensational" nature.  The Army Times is the New York Times of military papers.  And just as truth full and bias free.

If you pay attention almost every publication mentioning the dust test, is directly quoting the Army Times.



I'd also like to point out the DoD has an entire division dedicated to testing and evaluating small arms, even if/when there are no plans to replace current small arms.  The job is to test potential advancements in small arms and submit recommendations for further testing up the DoD chain.  From time to time these tests make the news.  Generally when a new weapon is tested by a big company seeking a mil contract, congress gets noisy about how the m4 is suddenly a bad weapon after reading the army times, or someone feels like doing an article of why this is so much better than the M4 or why the M4 is a poor weapon.



Have you checked the possible bolt drag issue in your LWRC?  On a few POF guns and at least one LWRC I know of the Cam Pin is marring the upper receiver when it unlocks as the bolt carrier yanks it back.  

Adams Arms offers a spring that slips over the bolt tail to keep it in the fully locked position until the cam pin fully cams.  More info here it also alludes to some issues (ones that are sometimes found on DI but not as much) that might be exacerbated buy running piston.  If I were running a piston that had that issue I'd just take the bolt carrier assembly with me to a hardware store and find a spring that works out of a parts bin.