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View Full Version : Concerning the Piston/Op-Rod/Short-Stroke AR-15


Asset
05-20-2011, 4:16 AM
It is my extremely humble opinion that this is the future of the short-stroke gas piston system.

http://www.adcorindustries.com/defense/weapons.asp

MrPlink
05-20-2011, 4:22 AM
the future is here. Its called the HK416, MR556, LWRC, ACR, SCAR etc etc etc

Nate87
05-20-2011, 4:27 AM
the future is here. Its called the HK416, MR556, LWRC, ACR, SCAR etc etc etc

+ 1

rareair
05-20-2011, 7:26 AM
Welcome to planet Earth, it is the year 2011

bwiese
05-20-2011, 9:25 AM
Fixing a problem that doesn't need to be fixed.

There's six, eight more more different gas piston designs for ARs. Not all these companies will be in business (i.e., no or limited replacement parts) 10 years from now.

Ruger and Colt (perhaps with Sig and perhaps LMT) will likely be the winners in the long term if you care to buy a piston rifle.

If you buy a gas piston AR from other vendors, you should buy multiple replacement parts for the whole system just to have on hand if the company goes belly up.

louscamaro91
05-20-2011, 9:29 AM
Fixing a problem that doesn't need to be fixed.

There's six, eight more more different gas piston designs for ARs. Not all these companies will be in business (i.e., no or limited replacement parts) 10 years from now.

Ruger and Colt (perhaps with Sig and perhaps LMT) will likely be the winners in the long term if you care to buy a piston rifle.

If you buy a gas piston AR from other vendors, you should buy multiple replacement parts for the whole system just to have on hand if the company goes belly up.



I agree with Bill,
Times change and so do weapons. Notice how tactical style rifle haven't been popular that long. Same concept goes for home construction.
That pepto bismol pink tile was the S*** in the 80's!

xfilterx
05-20-2011, 9:37 AM
Fixing a problem that doesn't need to be fixed.

Bill, can you elaborate on what you mean here? The 2007 Army Dust Tests would prove otherwise if I'm reading in to what you're saying accurately.

a1fabweld
05-20-2011, 10:10 AM
I'm perfectly satisfied with the proven DI system and see no need to convert to piston. I personally think the whole piston idea is a fad. Manufacturers feel the need to spice up the AR world & come out with all kinds of new products to attract buyers.

FeuerFrei
05-20-2011, 10:28 AM
Correct me if I appear to be wrong.
Olympic Arms made the first gas piston pistol years ago and they still make it.
They are still in business and you can get parts? Yes.

Going out of business is always a possible outcome for any manufacturer these days.
Unless the example is the Walt Langendorfer's Rhino Systems add on kit from years ago. Unsuccessful example of an add on kit.
The original AR15/M16 design is not the end all perfect weapon design.
It was the best that some one could sell the the military at that time.
I believe that Stoner was a great engineer and if he were to see what the current crop of changes made to his design he would be amazed.
DI vrs GP is an argument that will never be settled here. The world's armed forces are primarily armed with some sort of GP rifles and seem to be holding up rather well. Examples; AK, FAL, FNC, ARX160, SAR21, K2 and the list goes on.
I believe the Iranians are fielding a DI weapon though. (KH2002)
I have nothing against the DI system at all. I own a few.
My experience has shown me that a GP AR will be less finicky about what ammo it likes. YMMV.
Can the original AR design be altered to GP and still be a better rifle? I think so.

xfilterx
05-20-2011, 10:42 AM
Examples; AK, FAL, FNC, ARX160, SAR21, K2

SA80, G36...

bwiese
05-20-2011, 11:51 AM
Bill, can you elaborate on what you mean here? The 2007 Army Dust Tests would prove otherwise if I'm reading in to what you're saying accurately.

There are all sorts of tests out there. And companies need to sell something new into the market.

The AR15/M16 platform came in far ahead in actual performance ahead of a nominally reliable FAL/G1 rifle (piston rifle which included sand cuts) in 1st Desert Storm.

99.9% of individuals and soldiers are well-served by the AR15/M16/M4 platform. Certain behaviors of certain warriors running their guns in full auto to red-barrel-overheat may be improved by a piston system and barrel changes.

Most people do not realize going from DI to piston design actually adds more parts that can wear or fail and can stack reliability issues.

There is actually much more risk-to-failure in small volume design changes from small mfgrs than using standard production parts and design and minor incremental improvements that have stood the test of time (40+ yrs)

99% of individuals here do not need any of the limited/perceived advantages of piston designs. And if you wanna buy a gun because you like its fit, 'cool factor' or the way it looks, fine - be honest with yourself that you like it for that reason. If you just want a 100% reliable rifle/carbine, stick to an AR from a top -end manufacturer with a chromed barrel and quality USGI-derived parts.

I'm already hearing people returning/reselling their new piston rifles because they run some match ammo thru them and they are unhappy to find out they're not as accurate as a stock D.I. gas system rifle (due to various issues incl. the moving parts moving about while the bullet is in the barrel)

bwiese
05-20-2011, 12:07 PM
Correct me if I appear to be wrong.
Olympic Arms made the first gas piston pistol years ago and they still make it.
They are still in business and you can get parts? Yes.

Many folks are not fans of Oly Arms and consider them 'lower tier'. They've had some unique designs, but over the past 15 years I've had to help debug a lot of Oly Arms guns at the range. Some issues were user error (poor lube) but others weren't.

Making notes of AR platform reliability by using 3rd tier guns or 'parts guns' is invalid.
Guns are systems that are more than the sum of their pieces, and include ammo being specified as part of the system.


Going out of business is always a possible outcome for any manufacturer these days.

I'm confident that mfgrs with a broad line of firearms (Ruger and Sig), or Colt (due to historic gov't/agency relations history) will likely fare better over time than a smaller-volume company selling specialty rifles with unique parts.

Ruger esp is known for long term parts support and has such mfg capacity they do maching and casting work for other gun and non-gun manufacturers - and they have overall enough volume biz to work thru slow economies.

My experience has shown me that a GP AR will be less finicky about what ammo it likes. YMMV.

Your mileage has varied.

Any AR should run any quality ammo (poss. exception: weird light 45-50gr varmint loads designed for bolt guns and never intended for any gas guns). If an AR does not run a wide variety of ammo suitably, including Wolf and plastic-cased NATEC, it's defective - or the user is not following the TM and is running the gun unlubed or has never cleaned the chamber or doesn't have a chrome-lined barrel. [Some AR cycling reliability issues are also due to BulletButton-style maglocks being too tight, in combination with mags not necessarily being USGI profiles, causing drag on bolt carrier traversal.]

Yes, "YMMV" - you may have a bad rifle, out of spec, gas leak, fixed-magazine drag issues, crap ammo, etc.

All my AR rifles (reg'd AWs) run fine even when dirty. I use Colt and Bushmaster chrome-lined uppers and USGI magazines. Zero problems even when shot the crap out of with dirty Wolf ammo in the NV desert.


Can the original AR design be altered to GP and still be a better rifle? I think so.

Loss of accuracy, and risk substutition of increased risk are both very important to note. US soldiers have been making 500-600yd shots from M4A1HBs with 4X ACOGs in Afghan mountains (using 77gr SMK ammo). That is indeed helped by these Colt M4 HBs having very good quality barrels and QC, and even further assisted because nothing is banging around in the gun while the bullet's scooting down the barrel.

Please have some experience in manufacture of complex high-volume products before you say that adding parts/complexity reduces risk.

It doesn't - it just adds or substitutes other failure points that may either have higher risk and higher risk outcome, or incrementally 'stack' smaller risks into one combined larger risk that's larger than the original 'problem' that was intended to be 'solved'.

SoCalG
05-20-2011, 12:45 PM
Everybody has their own opinion, I think there's always room for improvement. After 40+ years, the AR (in my opinion) can be upgraded! The new test on the Sig 516was awesome.

FeuerFrei
05-20-2011, 12:47 PM
The arguments seem to be a little subjective with regard to DI vrs GP.
Troops making 500-600 yard/meter kills with an M4 + ACOG is not an argument in favor of DI. It can be just as easy to do the same with a GP fitted M4 + ACOG.
Shooting same ammo. Seems to be more of an example of good training to me.
DI is without a doubt a simple design. GP guns have 3 or 4 additional parts (+-). For example: most feature one piece carriers (sans gas key) seem to be very robust. No gas rings to fail.
GP guns are usually nose heavy because of more metal up front.
Most DI AR's with rails tend to be nose heavy too. Most customers tend to dress up the uppers with a rail from XYZ manufacture.
Anecdotal information galore on many firearms related forums that members post regarding "crappy wolf" ammo that won't cycle in their AR.
I agree a properly built DI AR will cycle all factory made ammo barring "special" loadings for hunting etc. all day long. Mine do.
Does adding a GP kit add risk to an AR rifle? Maybe so. I never said it did.
My opinion was that it made it better.
How? My opinion is that a properly set up GP AR will be easier on a user or new user to enjoy because the GP systems seem to be a little more forgiving when the user decides to not follow the SOP of AR care/maintenance. Many don't.
They are usually more forgiving with regard to ammo pressures as well.
If I were a manufacturer I want to sell a quality weapon. Period.
You CAN do it with a DI or GP rifle. I have seen it and have examples of it.

cmace22
05-20-2011, 12:54 PM
Long stroke designs like the PWS system dont seem to add to the parts count. Maybe 1 for the bolt spring. Other than that there are not many negatives to a well done piston system. There is a reason past and future designs are in fact GP. Far more proven military arms are GP not DI. There is no reason a system cannot be adapted to the AR and have it run just as good if not better than a DI set up.

Is it needed, 90% of the time no.

Can it add reliability, yes.

Is it worth the cost, thats on you.

To say there is no benefit is wrong.

The accuracy point is moot unless you are a precision/long range shooter.

Josh3239
05-20-2011, 1:48 PM
Bill, can you elaborate on what you mean here? The 2007 Army Dust Tests would prove otherwise if I'm reading in to what you're saying accurately.

We have all heard of that 2007 Army dust test, but I remain unconvinced. If the government can screw something up, they will. I wouldn't put it past them to put an old, beat up M4 that was either not properly lubed or overlubed run by a government employee who doesn't know squat, running magazines that had been sitting in the armory for years up against a brand spanking new HK416, properly lubed, operated by an H&K employee.

Until I hear otherwise about the conditions of the rifles I remain spectical. I realize the bias but I have seen other dust tests were the AR failed to fail and the acceptance of the rifle into the militarys of countrys all over the world doesn't lie. People claim the choice of the M16 was the result of a rigged election. If there was a true reliabilty problem they wouldn't be fielded here, they wouldn't be fielded in other nations from Canada to Europe and the Middle East.

Now the question I have for you is your telling me that those failures during the dust test were solely because of carbon created from the direct impingment? So the AR15 does fine in sand, it is the carbon deposited in the chamber? A gas piston doesn't block sand from entering the barrel, nor the chamber, nor the magazine. Additionally it doesn't stop stoppages from ammo, magazines, nor operator error. So it had to have been the carbon? I don't know, just doesn't add up to me. I think people here overestimate the power of a piston.


It was the best that some one could sell the the military at that time...

No gas rings to fail...

My experience has shown me that a GP AR will be less finicky about what ammo it likes. YMMV....

How? My opinion is that a properly set up GP AR will be easier on a user or new user to enjoy because the GP systems seem to be a little more forgiving when the user decides to not follow the SOP of AR care/maintenance. Many don't...

The world's armed forces are primarily armed with some sort of GP rifles and seem to be holding up rather well. Examples; AK, FAL, FNC, ARX160, SAR21, K2 and the list goes on.

The AR15 was really the only rifle in that particular class.

Non issue. ARs can and have operated without their gas rings. The gas rings are really more important now to scrape carbon off the inside of the carrier. The AR bolt is self cleaning, atleast in what needs to be clean for it to run.

Sorry, but that makes zero sense. They use the same barrel, same chamber, same upper receiver, same magazine, and same ammo. How can it be less "finicky"? If it is "finicky" with ammo that is a rifle issue.

Perhaps it would appear that way, but rifles don't break from carbon build up. Carbon creates friction which can cause stoppages, but that is why we use lubrication. It will soften the carbon and reduce friction. Despite the loud "I clean everyday" folks, I do believe they are in the minority. I've met many people who take little care of their AR and it continues to run (myself included). I know many people turn their noses at the practice (I had a Marine recruiter who was shocked at the carbon on my carrier and my Grandpa thinks that carbon will ruin your barrel) but what is the worst that can happen. It cannot break uppers, bolt, or barrels. And if it did (which it cannot), they aren't terribly expensive to replace.

To say that means little. It is the most popular system in this particular class of rifles. Just because that is the most popular gas system doesn't mean it is superior. The gas piston operation has been around for a long long time. The DI was the niche that reduced parts, weight, cost, and complexity. The gas piston is no doubt very proven. But to ignore the accomplishments of the DI would be an injustice.

Josh3239
05-20-2011, 2:02 PM
Other than that there are not many negatives to a well done piston system.

Not many, but they are there and IMO they outweight the pros. Maybe not for the people who buy a stock AR and change the grip and stock, but for people who like getting down to the details, it is too much of a problem. I like the flexiblity in gas block style and handguard style. I like the simplicity and the lesser amount of parts. I like that there is no recoil because of the gas system.

What other rifle on the planet can you as simply switch between a railed gas block with standard handguards to a low profile gas block hidden under a 12'' handguard and place the front sight wherever you want without drastic changes to the weapon and no additional recoil or parts?

There is a reason past and future designs are in fact GP. Far more proven military arms are GP not DI. There is no reason a system cannot be adapted to the AR and have it run just as good if not better than a DI set up.

Yes the gas piston is far more sucessful. But it sure seems like most members are taking the opinion, the gas piston is more successful therefore the DI is unsuccessful. And that just isn't the case, it isn't that black and white. Most members here should now that most popular doesn't necessarily mean best (otherwise Obama would be the best Prez, right?).

With the exception of the AK, I cannot think off the top of my head, any other gas piston rifle that has been as successful or more successful than the AR15. And one could certainly argue the AKs success being more credited toward the sheer amount of them that were made and what became of all of them after the fall of communism in Eastern Europe and Russia. The AR15 wasn't being manufactured by many countries 24/7 for 40 years than those countries fell and ended up in the hands of cartels, gun runners, arm dealers and any other hooligan. It was carefully sold or lisenced to friendly nations like Australia, England, Israel, South Korea, and the former South Vietnam. Even now they are slowly being moved into service with the new Afghani National Army who by the way are literally fighting for them.

Can it add reliability, yes.

I disagree. A gas piston fails to stop stoppages caused from operator error, bad ammo, and bad magazines. It doesn't stop foreign matter from entering the rifle. It doesn't stop parts breakage. All it does is limits the amount of carbon that can enter the rifle from firing. You are now redirecting most of where the carbon build up is. If you believe carbon build up can stop a rifle in the bolt group area, isn't it reasonable to believe that carbon build up can stop a rifle in the gas piston area? An area integral to self loading action that is much harder to lubricate.

CHS
05-20-2011, 2:12 PM
The difference between piston AR's and all of the other piston guns that people keep bringing up as examples of why the AR needs a piston is that those guns are unique and/or standardized.

Is there a standardized AR piston system? Absolutely not.

Personally, I see the AR piston system as fixing a problem that doesn't exist by replacing it with more parts, cost, weight, and complexity. There is actually more to go wrong with an AR piston system than with a DI.

DI works great. It's simple, lightweight, reliable and STANDARDIZED.

If I need a gas tube replaced on my AR next year, who am I going to buy it from? It doesn't matter! I can get it from anyone because they're all the same.

If I need an op-rod replaced for my piston system next year, who am I going to buy it from? Who knows. The company might be out of business next year. Or maybe they're still around but have completely changed their platform? (Ahem, PWS). But the bottom line is, I can't just go out and buy a standardized op-rod, because there is no such thing.

On top of that, all of the designers of AR piston systems are doing it wrong. Notice how they're not using a railed receiver like EVERY OTHER PISTON GUN IN THE WORLD? Instead they keep using the same DI receiver that's designed for straight rearward motion, something that no piston system delivers. To properly design a piston system for the AR platform, one must replace not just the gas tube, but the entire receiver. But at that point, is it really still an AR anymore? It's just an AR lower with a completely different upper slapped on. That would make it an entirely different gun in my opinion. And that's fine. Go design a different gun, make it a piston on a railed receiver. Maybe even use some design hints from the AR (Ahem, ACR and SCAR), and get it adopted by the military as a STANDARDIZED arm (ahem, SCAR), and maybe you're onto something. But then you no longer have an AR.

So leave the pistons off the AR and get a different gun that was designed from the ground up to utilize a piston.

Uriah02
05-20-2011, 2:42 PM
From what I've gathered on the issue, with a 20" the GP isn't necessary becuase the DI was designed for a 20" barrel. As barrel lengths are reduced the more the GP's differences cash in. Maybe I just drank the cool aid? What say the masses?

CHS
05-20-2011, 2:56 PM
From what I've gathered on the issue, with a 20" the GP isn't necessary becuase the DI was designed for a 20" barrel. As barrel lengths are reduced the more the GP's differences cash in. Maybe I just drank the cool aid? What say the masses?

Sort of.

The gas system length does need to be tuned to the barrel length. The problem with the M4 Carbine is that it originally started off life as the Colt Commando, with an 11.5" barrel. The carbine gas system length was tuned for the short barrel. The problem was that the barrel was too short to get decent performance out of the 5.56 rounds of the day, so they lengthened the barrel out to 14.5" which gave the 5.56 round better terminal performance, but now you had the bullet in the barrel for too long, increasing gas system pressure which can cause some issues. Midlength gas systems fix this problem, and 20" rifles with rifle gas systems are fine. 11.5" guns are fine as well :)

However, that doesn't mean that the proper "fix" for the M4 is a piston.