AR15 Gas piston uppers
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Chris Rhines
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From what I've seen of them, they are less reliable than the conventional AR.
- Chris
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Dave Rishar
Member
Disadvantages?
Needless complication, primarily. The current system has worked for 40 years. Gas pistons were not a secret when Stoner designed the weapon. He did not choose DI accidently, or simply to be contrary.
The reliability issue is often touted. I remain unconvinced that one is noticably better than the other in this department. DI probably gets dirtier per shot. Most AR's don't seem to mind it. It's important to remember that when most argue the inherant reliability of piston designs, they're (perhaps inadvertantly) referring to arms like the AK or M1/M14 that use an op rod as well and probably gain their reliability more due to having such a large reciprocating mass than anything, something most (if not all) AR piston uppers don't seem to share. Many piston-operated weapons that lack such a mass don't do nearly as well. Just having a piston in there doesn't necessarily fix anything.
Sometimes I get the impression that piston uppers are more about selling stuff than improving stuff, but that's just my take on it. Others feel differently.
I smell a 9mm vs. .45 debate coming up.
Needless complication, primarily. The current system has worked for 40 years. Gas pistons were not a secret when Stoner designed the weapon. He did not choose DI accidently, or simply to be contrary.
The reliability issue is often touted. I remain unconvinced that one is noticably better than the other in this department. DI probably gets dirtier per shot. Most AR's don't seem to mind it. It's important to remember that when most argue the inherant reliability of piston designs, they're (perhaps inadvertantly) referring to arms like the AK or M1/M14 that use an op rod as well and probably gain their reliability more due to having such a large reciprocating mass than anything, something most (if not all) AR piston uppers don't seem to share. Many piston-operated weapons that lack such a mass don't do nearly as well. Just having a piston in there doesn't necessarily fix anything.
Sometimes I get the impression that piston uppers are more about selling stuff than improving stuff, but that's just my take on it. Others feel differently.
I smell a 9mm vs. .45 debate coming up.
Chris Rhines
Member
Difference between intention and effect, I guess...
- Chris
SigfanUSAF
Member
9mm v. 45ACP debate? Gas-piston v. DI? What about 5.56mm v. 7.62mm?
Gimme an M1A in my hands with a 1911A1 in my holster, and I'm happy as can be.
Anyone can modify a firearm. A genius improves one. I'm the former, but agree with Mr. Rishar. Go with what has worked for 40+ years.
How many TRUE improvements have been made on the 1911, for example? Mods to feed modern loads, mods for comfort, heck, in most cases we revert back to the original flat mainspring housing.
Sorry to have diverted, but I firmly believe Mr. Stoner knew what he was doing.
Gimme an M1A in my hands with a 1911A1 in my holster, and I'm happy as can be.
Anyone can modify a firearm. A genius improves one. I'm the former, but agree with Mr. Rishar. Go with what has worked for 40+ years.
How many TRUE improvements have been made on the 1911, for example? Mods to feed modern loads, mods for comfort, heck, in most cases we revert back to the original flat mainspring housing.
Sorry to have diverted, but I firmly believe Mr. Stoner knew what he was doing.
saltydog
Member
Nah, I double tap both my 9 and my 45 so I could care less.
Langenator
Member
The advantages are that your not dumping as much heat and carbon into the upper receiver and moving parts. If you're not doing sustained heavy firing, that probably doesn't matter a whole lot to you.
Personally, I'm thinking of buying one for the simple reason that I do like ARs, but I hate cleaning the carbon off of basically everything.
Personally, I'm thinking of buying one for the simple reason that I do like ARs, but I hate cleaning the carbon off of basically everything.
DMK
Member
It's basically a solution in search of a problem.
I love when folks tout it as new tech.
For a gun that craps where it eats...
It's not a bad idea. Those that I've seen could probably stand some refinement, but I'd wager 2nd generation AR15 gas piston uppers will be around the corner soon.
Never did like the M16 in my 20+ year military career, but I cleaned each one I was issued like there was no tomorrow.
It's not a bad idea. Those that I've seen could probably stand some refinement, but I'd wager 2nd generation AR15 gas piston uppers will be around the corner soon.
Never did like the M16 in my 20+ year military career, but I cleaned each one I was issued like there was no tomorrow.
Dave Rishar
Member
In my own experience, M16A3's undergoing heavy firing (defined, in my case, to be a rate of fire that melts the handguard and/or destroys the gas tube) don't choke on the carbon or heat. The weapon is still operating properly at the point where one can no longer hold it without gloves. Once it cools down, though -- well, that is a different story. I don't see a piston helping with that sort of heat however. The barrel is often trashed after this and the operating system won't fix that.
As for the cleaning issue, I will accept that. I've never had to clean a piston AR but I can't imagine it being any dirtier than a DI. It's not that bad, though; my preferred method is to scrape the worst of the carbon off with a stripper clip, soak everything down well with oil or solvent, and start scrubbing. There are only a few spots where the carbon really builds up and even then, it's not that big of a deal.
It's worth repeating that the gas piston (and direct impingement, for that matter, which was ~50 years old when Stoner considered it) are not new solutions to anything. They're merely different roads leading to the same destination. For the M16/AR-15, and what it's meant to do, it's my belief that DI is just fine. For something else, other rules apply.
Let us return to the OP's question: assuming an equal build quality, are there any disadvantages to a piston upper from a purely theoretical standpoint? I submit the following:
1. Unnecessary complication.
2. Added weight.
3. Increased/altered recoil impulse.
4. Increased parts count.
5. Fouling concerns with gas system.*
6. Cleaning concerns with gas system. **
* You know and I know that a properly designed and manufactured gas cylinder and piston are essentially self-cleaning; however, consider every time that someone has posted on here or somewhere else about how their gas piston isn't moving freely under gravity due to fouling and such, and think about how many DI AR users have complained that their gas tube was blocked. There's something to be said for the AR's gas tube in this regard.
** Clean rightside-up if the gas system is on top and upside-down if it's underneath, right? So says the manual, because we don't want solvents and oil getting in there and dieseling or coking later. Now, it's theoretically possible that the same thing can happen in a DI but really, does it?
There are probably some things that I'm missing. More additions are welcomed. Let's answer the OP's question.
As for the cleaning issue, I will accept that. I've never had to clean a piston AR but I can't imagine it being any dirtier than a DI. It's not that bad, though; my preferred method is to scrape the worst of the carbon off with a stripper clip, soak everything down well with oil or solvent, and start scrubbing. There are only a few spots where the carbon really builds up and even then, it's not that big of a deal.
It's worth repeating that the gas piston (and direct impingement, for that matter, which was ~50 years old when Stoner considered it) are not new solutions to anything. They're merely different roads leading to the same destination. For the M16/AR-15, and what it's meant to do, it's my belief that DI is just fine. For something else, other rules apply.
Let us return to the OP's question: assuming an equal build quality, are there any disadvantages to a piston upper from a purely theoretical standpoint? I submit the following:
1. Unnecessary complication.
2. Added weight.
3. Increased/altered recoil impulse.
4. Increased parts count.
5. Fouling concerns with gas system.*
6. Cleaning concerns with gas system. **
* You know and I know that a properly designed and manufactured gas cylinder and piston are essentially self-cleaning; however, consider every time that someone has posted on here or somewhere else about how their gas piston isn't moving freely under gravity due to fouling and such, and think about how many DI AR users have complained that their gas tube was blocked. There's something to be said for the AR's gas tube in this regard.
** Clean rightside-up if the gas system is on top and upside-down if it's underneath, right? So says the manual, because we don't want solvents and oil getting in there and dieseling or coking later. Now, it's theoretically possible that the same thing can happen in a DI but really, does it?
There are probably some things that I'm missing. More additions are welcomed. Let's answer the OP's question.
IZinterrogator
Member
They are more reliable in barrel lengths like 11.5". Since most of us don't own an AR that short thanks to the NFA, it's a moot point.
That being said, I wouldn't mind having one to try out, but only if it said Colt on the side.
Colt did play with the gas piston system for a bit...
McNamara and his cronies didn't want anybody messing with the existing design, so the Army skipped Colts' next iteration: (Picture credits go to Badger Arms)
As for Stoner's adaptation of the Direct Impingement gas system being the epitome of the design, I heartily disagree. My 1942 vintage AG-42B Ljungman is also direct impingement, and considerably cleaner in operation than any AR-15 and M16 I've ever owned or been issued. Note to gun designers who absolutely must use direct impingement operation - don't route combustion products through the bolt carrier, mmmkay?
McNamara and his cronies didn't want anybody messing with the existing design, so the Army skipped Colts' next iteration: (Picture credits go to Badger Arms)
As for Stoner's adaptation of the Direct Impingement gas system being the epitome of the design, I heartily disagree. My 1942 vintage AG-42B Ljungman is also direct impingement, and considerably cleaner in operation than any AR-15 and M16 I've ever owned or been issued. Note to gun designers who absolutely must use direct impingement operation - don't route combustion products through the bolt carrier, mmmkay?
Lebben-B
Member
I own a POF-USA upper (It was my present to myself after I got back from Iraq.) A couple of points:
Reliability - I have experienced superior reliability with the POF over my DI AR and my issue rifles. Through 3K over the last seven months, I've had nary a problem with the POF. The first 1000 rounds were fired with no lube and no cleaning, just to see how reliable the system was. The POF performed to spec with zero issues.
Maintenance - In reality, this is a zero sum game. Yes, the receiver halves, bolt group and chamber stay cleaner on my POF. But the carbon has to go somewhere and that somewhere is the piston system (piston, piston sleeve, gas plug, and tappet.) Other than that, normal -10 maintenance applies.
Recoil - The recoil impulse is different. Not harder or more pronounced, just different.
Complexity - The POF system replaces a gas tube, and bolt carrier group with a gas plug, piston, sleeve, tappet and modified BCG. (The LW system uses a tappet, spring and a gas cup, IIRC) Yes, it adds parts but those parts actually increase the reliability of the rifle by keeping waste heat and material from reaching the BCG and receiver. As previously stated, this really becomes an advantage with shorter barrelled uppers and while firing with a supression system since there's very little issue with gas blowback and dwell time.
Weight - This is an issue, at least with the POF system. The POF piston system makes the AR noticably nose heavy. It doesn't require herculean effort to put the sights on target, but the system is more weighty than a comparable AR/M16 series/M4.
So what are the disadvantages to a gas piston system? Weight and a different maintenance emphasis. Some posters in other threads have pointed out that the US has used a DI rifle for over 40 years. And then go on to state (usually) that gas piston systems are an answer in search of a question or somesuch pithy comment. Consider this: If the DI system is the end all/be all of gas operating systems, why did it languish as a firearms footnote until Stoner made it work acceptably well? DI is deceptively simple. Yes, it requires fewer working parts. But it demands that those parts be finely made with tight tolerances in order to achieve a proper gas seal.
Mike
Reliability - I have experienced superior reliability with the POF over my DI AR and my issue rifles. Through 3K over the last seven months, I've had nary a problem with the POF. The first 1000 rounds were fired with no lube and no cleaning, just to see how reliable the system was. The POF performed to spec with zero issues.
Maintenance - In reality, this is a zero sum game. Yes, the receiver halves, bolt group and chamber stay cleaner on my POF. But the carbon has to go somewhere and that somewhere is the piston system (piston, piston sleeve, gas plug, and tappet.) Other than that, normal -10 maintenance applies.
Recoil - The recoil impulse is different. Not harder or more pronounced, just different.
Complexity - The POF system replaces a gas tube, and bolt carrier group with a gas plug, piston, sleeve, tappet and modified BCG. (The LW system uses a tappet, spring and a gas cup, IIRC) Yes, it adds parts but those parts actually increase the reliability of the rifle by keeping waste heat and material from reaching the BCG and receiver. As previously stated, this really becomes an advantage with shorter barrelled uppers and while firing with a supression system since there's very little issue with gas blowback and dwell time.
Weight - This is an issue, at least with the POF system. The POF piston system makes the AR noticably nose heavy. It doesn't require herculean effort to put the sights on target, but the system is more weighty than a comparable AR/M16 series/M4.
So what are the disadvantages to a gas piston system? Weight and a different maintenance emphasis. Some posters in other threads have pointed out that the US has used a DI rifle for over 40 years. And then go on to state (usually) that gas piston systems are an answer in search of a question or somesuch pithy comment. Consider this: If the DI system is the end all/be all of gas operating systems, why did it languish as a firearms footnote until Stoner made it work acceptably well? DI is deceptively simple. Yes, it requires fewer working parts. But it demands that those parts be finely made with tight tolerances in order to achieve a proper gas seal.
Mike
LoadedDrum
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I do not get the complication complaint either.
For instance, with the POF, you lose 3 gas rings which are wear items in a DI AR. When was the last time you wore out a gas piston? You also lose the staked on carrier key and requisite bolts. Three less things to get loose and marr your upper with. The parts that a piston adds do not wear (except for the spring in the LW).
Okay, the gas system is adjustable. All that means is set your gas system for the lowest setting that will reliably cycle your most commonly shot ammo and enjoy less recoil and wear on your AR. When you do run into that bad batch of Wolf or what ever, just crank it up one. Not that complicated.
For instance, with the POF, you lose 3 gas rings which are wear items in a DI AR. When was the last time you wore out a gas piston? You also lose the staked on carrier key and requisite bolts. Three less things to get loose and marr your upper with. The parts that a piston adds do not wear (except for the spring in the LW).
Okay, the gas system is adjustable. All that means is set your gas system for the lowest setting that will reliably cycle your most commonly shot ammo and enjoy less recoil and wear on your AR. When you do run into that bad batch of Wolf or what ever, just crank it up one. Not that complicated.
chieftain
Member
There is/was a good reason no other successful fighting weapon has Gas impingement.
Someone said it earlier, don't S**T where you eat.
Problems with the extractor, piston rings, and wear factors on the bolt carrier.
Some one else said, "it has worked for 40 years." Mainly when no one was shooting at our troops.
There are reasons the Army wanted to replace the AR system. one word RELIABILITY. I believe the only reason we didn't is the cost. Needed the money for other stuff.
With the right bullets we can get by with the caliber. I prefer a 'better' one, like one of the newer proposed 6.5/6.8 type used.
I policed up Dead Marines in 1967 with their brand new M16-E1 model rifles were in parts around them. Let's just say it left an impression.
In 2003 we had a whole support unit was virtually wiped out because their rifles couldn't function. Dirty, no doubt. (think Jessica Lynch) Never did hear of that happening in one of our other wars, where the AR system wasn't used.
There was a reason. 35 years later, and American troops dying for the same reason. their M16 would not function in combat.
Looks like we may have to go back to the Frozen Chosin soon too. I ain't so sure that the Matty Mattel will cut it under the winter conditions there either.
I don't know who has the best piston weapon, POV, Robinson, Hk, SIG, FN, Armalite but I bet one of them has one that is acceptably reliable right now. I doubt I know everyone that is making a piston impingement system.
And let's not forget HK's earlier Delayed roller locking system either. It was known for it's reliability.
go figure.
Fred
Someone said it earlier, don't S**T where you eat.
Problems with the extractor, piston rings, and wear factors on the bolt carrier.
Some one else said, "it has worked for 40 years." Mainly when no one was shooting at our troops.
There are reasons the Army wanted to replace the AR system. one word RELIABILITY. I believe the only reason we didn't is the cost. Needed the money for other stuff.
With the right bullets we can get by with the caliber. I prefer a 'better' one, like one of the newer proposed 6.5/6.8 type used.
I policed up Dead Marines in 1967 with their brand new M16-E1 model rifles were in parts around them. Let's just say it left an impression.
In 2003 we had a whole support unit was virtually wiped out because their rifles couldn't function. Dirty, no doubt. (think Jessica Lynch) Never did hear of that happening in one of our other wars, where the AR system wasn't used.
There was a reason. 35 years later, and American troops dying for the same reason. their M16 would not function in combat.
Looks like we may have to go back to the Frozen Chosin soon too. I ain't so sure that the Matty Mattel will cut it under the winter conditions there either.
I don't know who has the best piston weapon, POV, Robinson, Hk, SIG, FN, Armalite but I bet one of them has one that is acceptably reliable right now. I doubt I know everyone that is making a piston impingement system.
And let's not forget HK's earlier Delayed roller locking system either. It was known for it's reliability.
go figure.
Fred
SigfanUSAF
Member
Here is a fact. Any firearm is going to require some level of cleaning. I've had to stop shooting my #4 mk 1 after hundreds of consecutive rounds due to the fact the bolt wouldn't close. The chamber became too gummed up. This is especially true for any semi-auto. I was a 2A551B MOS, so I never experienced a firefight situation with my A2, but always took the time to clean it thoroughly after every use (try it while flying in a 130 in incliment weather!!). As with any machined object with moving parts, any buildup of anything in between parts may cause a problem. The tight tolerances of the AR system are its biggist downfall, IMHO. The Hk roller locked rifles, AKs, etc have much more forgiving clearance, which allows them to be inherently more reliable. Considering the original design of the direct gas operated AR/M16, its incredibly reliable for what it is.
Bartholomew Roberts
Member
Is the POF bolt a proprietary bolt different from the normal AR15 bolt? Because in a normal AR15 bolt, the gas rings also bear the load as the bolt moves in the carrier. This is why the bolt in a LW gas piston system must have gas rings to function even though there is no longer any gas being routed to it.
Lebben-B
Member
The POF bolt is a standard AR bolt, sans gas rings. IIRC, LW left the gas rings on his system to ensure the bolt stayed stable as it moved inside the carrier.
Mike
Bartholomew Roberts
Member
Hmmm, that is interesting - have you noticed any signs of increased wear on the lugs or bolt bounce compared to a regular AR15 bolt?
Makes me wonder how critical that part is to proper function if one gas piston manufacturer is not using gas rings at all and another is. Even a direct impingement AR can run fine on a single gas ring... I wonder how much of a role keeping the bolt stable plays in reliability or longevity?
Lebben-B
Member
I haven't had any increased wear on the bolt lugs nor is there any more wobble or bounce in the bolt than in a standard AR. That said, the bolt moves freely back and forth inside the carrier. I think Paul left the rings there as a redundant system, "just in case."
It's also interesting to note that the POF system doesn't use a return spring for the tappet, as the LW system does.
Mike
DMK
Member
FWIW, I've had both a FAL and SKS choke on carbon built up in the gas tube (obviously from the lack of cleaning, I used to think the piston and tube didn't need cleaning). The gas piston design doesn't solve that problem. It just moves the problem somewhere else.
Exposure
Member
I got to play with a 9.25 inch POF upper in full auto a couple of weeks ago.
I really liked it. Seems like a well built, great performing upper to me. Granted my time on it was far to brief to make any kind of assesment but as a whole I thought it was a really interesting take on the whole AR-15/M-16 platform.
It sure did attract a lot of attention at the range and functioned very reliably through magazine after magazine.
Throws quite a fireball too with the 9.25 inch barrel!
I really liked it. Seems like a well built, great performing upper to me. Granted my time on it was far to brief to make any kind of assesment but as a whole I thought it was a really interesting take on the whole AR-15/M-16 platform.
It sure did attract a lot of attention at the range and functioned very reliably through magazine after magazine.
Throws quite a fireball too with the 9.25 inch barrel!
I have the Leitner-Wise rifle. I got is in mid-December of '05. After about 2500-3000 rounds through it here are my observations.
Recoil impulse is definitely different. I can't really explain it, but it seems to be quicker, if that makes sense.
Reliability. I have never been in a position to really test that. Though, I will say this. The bolt, carrier, chamber, etc stay much cleaner and cooler. Cleaning is just as simple as wiping the parts off.
There are about 4 extra moving parts. The weight is negligible. I can't subjectively feel any difference when compared to similar configured DI rifles.
Maintenance of the piston system itself. None, so far. It does blow some junk on the front sight base and on the last .5 inch of the top rail. These are not moving parts so I don't worry about it much. The front sight wipes off easily. The inside of the rail does get a very small amount of carbon built up then it seems to not add any more. I no longer worry about it.
BTW, the piston parts look nothing like the monstrous things in that Colt drawing above. Most people who look at my rifle don't even know that it is a piston system until I show them. In fact, only one guy figured it out and that was from the name on the side.
Recoil impulse is definitely different. I can't really explain it, but it seems to be quicker, if that makes sense.
Reliability. I have never been in a position to really test that. Though, I will say this. The bolt, carrier, chamber, etc stay much cleaner and cooler. Cleaning is just as simple as wiping the parts off.
There are about 4 extra moving parts. The weight is negligible. I can't subjectively feel any difference when compared to similar configured DI rifles.
Maintenance of the piston system itself. None, so far. It does blow some junk on the front sight base and on the last .5 inch of the top rail. These are not moving parts so I don't worry about it much. The front sight wipes off easily. The inside of the rail does get a very small amount of carbon built up then it seems to not add any more. I no longer worry about it.
BTW, the piston parts look nothing like the monstrous things in that Colt drawing above. Most people who look at my rifle don't even know that it is a piston system until I show them. In fact, only one guy figured it out and that was from the name on the side.
Depends on the gun, I guess...
I've done that same test with an AK or two, and left the gas tubes and pistons exceptionally cruddy with nary a problem. Especially with some "filthy" H335 handloads that weren't the cleanest burning choices in ammo. Of course, cleanup later was considerably easier than an AR/M16.
I've done that same test with an AK or two, and left the gas tubes and pistons exceptionally cruddy with nary a problem. Especially with some "filthy" H335 handloads that weren't the cleanest burning choices in ammo. Of course, cleanup later was considerably easier than an AR/M16.
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