Standard Gas Impingement System or Gas Piston operated System

[jdavis1776]

Which is the more reliable method of gas operated system. The standard gas impingement system or the gas piston system?

[Cameron]

Definitely the standard direct impingement system, 100% reliable.
The piston is a solution looking for a problem.

Cameron

[TehLlama]

Rough topic, and I'd do some further research on your own first...

A good iteration of each with proper materials used and good parts will run, a poor quality version of both will still choke. There are many cases where subpar weapons are used as hosts for poor quality gas piston modifications, the net result being something that is just as unreliable AND weighs more.

Once the op-rod piston setups are mature, they seem like an ideal solution for ClassIII weapons (Suppressed, SBR, Fully Automatic; or any combination thereof), but for more pedestrian rifles you needn't look past DI for something that works.

[Quib]

Here's a topic along similar lines......http://www.weaponevolution.com/forum/showthread.php?2555-Had-an-interesting-conversation-yesterday-want-to-get-your-thoughts.

[AR-10]

I'm not a piston hater, but I have yet to replace a gas tube on any of my uppers and the ONLY time I've had an issue with reliability was when I played around with different buffer weights and got one of my uppers to short stroke.

You're more likely to have a mag or ammo-related failure than a gas tube or piston failure.

[5pins]

With the piston you are adding more parts that can potentially fail.

[Muddyboots]

The AR platform wasn't designed to use a piston to push on the carrier. It was designed so the push would be concentric and from inside. The bolt IS the piston in a gas gun, that's why it has those little tiny piston rings. A rod pushing on something where the gas key was causes some designs to cant. If nothing else, it adds more parts and thus more gremlin bait.

Muddyboots

[deadduck357]

I have heard the same complaint against the piston system AR's since the first ones came out, "the piston is a solution looking for a problem", its getting about as old as "I inherited it from the past administration". Some have been saying this from the first piston AR then the second and so on and so on and now today there are many AR companies producing piston AR's that the same old complaints cannot be legitimate any longer.

The U.S. Military has also requested the DOD for an updated M4 and one of the updates listed is for it to have a "piston type operating system".

It is evolution, the AR15/M16/M4 history is all about its evolution, there has been so many upgrades and changes to improve the design, why would it stop.

Back to the OP, "Which is the more reliable method of gas operated system", well they both are. The DI is tried and true, battle proven, interchangeable parts throughout the industry. It is the standard by which all are to be compared. But it does POOP where it eats, will this effect you,no,not as long as you clean and lube on a regular routine.

Pistons are normally a little heavier than the DI counterpart. Pistons don't transfer the heat, gases or fouling into the BCG keeping the system running cool and clean. There is no real standardization between each manufacturers piston system parts.

You have to decide if you like a light weight AR that requires regular maintenance OR an AR that requires very little maintenance with a little extra weight.

Either way, they are both good systems, I have multiple of both and really cannot knock either, I just like that it takes me about half the time to clean my pistons as it does to clean my DI AR's.

[rob_s]

so that's what this all comes down to, easier to clean? Seriously? Hevier, more expensive, proprietary parts, often sub-standard parts, new issues like carrier tilt, etc. just to make it easier to clean? Dear God.

I would also point out that, while the piston crowd likes to point to the fact that the US Military keeps asking for pistons, the same US Military has yet to actually commit to a piston in any real quantity, and in several instances has had the opportunity to choose a piston solution has instead gone with the DI. Asking for something and then deciding it's not up to par and sticking with the legacy system speaks volumes IMHO.

[Paulo_Santos]

I wish we had piston ARs at my job and cleaning would be a main reason. After a week of qualifying everyone, guess who gets to clean all of the carbines? The firearms instructors do. And guess who gets stuck with cleaning the carbines and shotguns? I do. Takes me several hours to clean all of them. If we had piston ARs, it would take me minutes to wipe them down. I'm sure the Military would be the same. Spends more time cleaning your AR as opposed to spending a few minutes wiping them down. All of the negatives about the piston ARs are overblown. Matter of fact, the piston AR replaces one of the most problematic parts of the DI, which is the carrier key. JMHO.

[Quentin]

As far as the military wanting to replace DGI with a piston, well of course the reverse happened in the mid 1960s when the US Armed Forces adopted the M16 over the M14. There have been many worthy challengers over the last 40+ years and countless critics but look what's still in the throne. No doubt there are good reasons to test new designs but for now - long live the king!

[Eric]

I guess part of the equation should include what role it will play.
If this is your only carbine, I would without question go DI. Parts availability also can come into play. The various piston parts are essentially proprietary, as opposed to the more generic parts involving the DI system.

[Eric]

After a week of qualifying everyone, guess who gets to clean all of the carbines? The firearms instructors do. That sucks. Our carbines are issued per Officer, or a private purchase item. No pool guns.

[reiswigt]

While I hate to whack a hornets nest, here goes.

I like my piston ARs, I will be getting a couple DI ARs soon.

Whether the government has/hasn't or will/won't choose a piston system over a DI system is not a valid support to argue the merits of a systems validity, it's superiority or it's value. Our government and military are notorious for making poor choices and continuing to support and perpetuate them.

I personally think that some of the love and hate that comes out where ever this debate arises is unfounded and irrational.

[peabody]

i like my DI guns.

for what i do , they are great.

wishes i had a job cleaning guns, be better than pushin this ol' semi.


peabody

[Paulo_Santos]

That sucks. Our carbines are issued per Officer, or a private purchase item. No pool guns.

I wish we could have our own Personally owned guns. Our chief doesn't like that idea. Not many NJ departments allow personally owned AR's, which sucks.

[rob_s]

IAll of the negatives about the piston ARs are overblown.

All? Seriously? When the only benefit anyone is clinging to now is "easier to clean" in the era where anyone with any experience with the legacy system will tell you that it doesn't need to be cleaned at nearly the interval that some used to think and that if cleaning is really what one is primarily concerned with there are fancy new coatings that help in that regard?

You may think they are worth the trade-off, but there are downsides to the piston system.
Heavier
More expensive
Sub-standard parts (FCG, barrel, etc. used by many makers)
Proprietary parts (I know you think this is a non-issue, but I think your'e way wrong on that, and can expound on why)
New, unique problems (carrier-tilt is but one)
Re-located fouling (it doesn't go away, it just goes someplace else)

These are all real issues that exist. Whether or not they are woth the trade off for a gun that offers no advantage other than it may be easier to clean is a personal choice, but it is not making these issues go away anytime soon.

The reality is that there is nothing wrong with the legacy system. The detractors have blamed the direct gas impingement system for reliability issues, pointed to stacked, flawed tests that were later refuted or reversed to suppor their claims, and generally relied on a very shallow basin of knowledge and the relative ignorance of their audience to make their points. The problem is that when you have an educated user, with extensive experience with the system, who understands the realities of the DI system as well as the history of it's design, there is effectively nothing wrong with it and in some ways it is in fact superior.

[5pins]

Matter of fact, the piston AR replaces one of the most problematic parts of the DI, which is the carrier key. JMHO.

A properly installed gas key will not cause problems.

At some point some of the companies making these piston systems are going to either stop or go under. If you make the wrong choice now you may be stuck without spare parts.

As far as pooping where it eats, I don’t care if it licks itself, so long as it works. Here is a couple of articles on the reliability on the direct impingement system.

http://www.facebook.com/l.php?u=http%3A%2F%2Fwww.bravocompanymfg.com%2Fv%2 Fvspfiles%2Fassets%2Fimages%2Ffilthy14_oct10.pdf&h=28945

http://www.defensereview.com/the-big-m4-myth-fouling-caused-by-the-direct-impingement-gas-system-makes-the-m4-unreliable/

[AR-10]

I stake my own keys with a MOACKS and I've never had one come loose.

I don't own any pistons yet, but I do get to shoot one pretty often and I can tell you one thing - they do get dirty especially with systems that bleed off the leftover pressure under the handguard.

Here is a pic of a suppressed HK416 that suffered a failure to fire at a carbine class when a chunk of carbon wedged itself in the fire controls (courtesy of new-arguy):

http://img688.imageshack.us/img688/1286/35486894878449978d0eb.jpg

[Paulo_Santos]

All? Seriously? When the only benefit anyone is clinging to now is "easier to clean" in the era where anyone with any experience with the legacy system will tell you that it doesn't need to be cleaned at nearly the interval that some used to think and that if cleaning is really what one is primarily concerned with there are fancy new coatings that help in that regard?

You may think they are worth the trade-off, but there are downsides to the piston system.
Heavier
More expensive
Sub-standard parts (FCG, barrel, etc. used by many makers)
Proprietary parts (I know you think this is a non-issue, but I think your'e way wrong on that, and can expound on why)
New, unique problems (carrier-tilt is but one)
Re-located fouling (it doesn't go away, it just goes someplace else)

These are all real issues that exist. Whether or not they are woth the trade off for a gun that offers no advantage other than it may be easier to clean is a personal choice, but it is not making these issues go away anytime soon.

The reality is that there is nothing wrong with the legacy system. The detractors have blamed the direct gas impingement system for reliability issues, pointed to stacked, flawed tests that were later refuted or reversed to suppor their claims, and generally relied on a very shallow basin of knowledge and the relative ignorance of their audience to make their points. The problem is that when you have an educated user, with extensive experience with the system, who understands the realities of the DI system as well as the history of it's design, there is effectively nothing wrong with it and in some ways it is in fact superior.

Hey you like DI, I like both. They are still ARs. I've had my LMT for almost 2 years and have heard all of the so called negatives and I just don't see it. Maybe I'm just laid back and just don't care or maybe it is something else that I'm missing. All I know is that j have fired my LMT side by side with my friend's Colts and Bushmasters and I wouldn't trade it for anything. Even my friends are amazed on how smooth it shoots.

[deadduck357]

so that's what this all comes down to, easier to clean? Seriously? Hevier, more expensive, proprietary parts, often sub-standard parts, new issues like carrier tilt, etc. just to make it easier to clean? Dear God.

I would also point out that, while the piston crowd likes to point to the fact that the US Military keeps asking for pistons, the same US Military has yet to actually commit to a piston in any real quantity, and in several instances has had the opportunity to choose a piston solution has instead gone with the DI. Asking for something and then deciding it's not up to par and sticking with the legacy system speaks volumes IMHO.

I don't think it's as easy as that, $Cost$ is a major concern and time to swap and train a new system while in an ongoing war is not feasible.

[peabody]

call me crazy.... but back when i was just starting to learn about AR's..... i used an lincoln arc welder on the carrier key bolts.

gotta admit , they've never ever came loose again.

peabody

[TehLlama]

call me crazy.... but back when i was just starting to learn about AR's..... i used an lincoln arc welder on the carrier key bolts.

gotta admit , they've never ever came loose again.

peabody

The only downside for that is that the carrier unitized to the gas key means that a broken/bent/borked gas key would be a bigger hassle. I'm curious where you put the welds to avoid friction points...

[Creeky73]

in my worthless opinion, a lot of the issues about parts availability because of piston being proprietary parts can be remedied if you do a piston conversion to a DI rifle, because you can always switch that back. If you buy a ready-made piston rifle, or build your own, you might not be able to do this so easily. In my case, I built mine and the barrel did not come tapped for a standard FSB, and I am using an Adams Arms kit with mine. Switching to DI would obviously be more difficult since I am restricted to finding a bolt-on gas block or having to have someone tap it for a standard front sight. If you do a conversion, you obviously don't have this issue. There are supposed to be a couple of good piston conversion kits out there, with Adams Arms and Osprey getting a lot of praise. Just keep the old parts, and you are good.

[Paulo_Santos]

in my worthless opinion, a lot of the issues about parts availability because of piston being proprietary parts can be remedied if you do a piston conversion to a DI rifle, because you can always switch that back. If you buy a ready-made piston rifle, or build your own, you might not be able to do this so easily. In my case, I built mine and the barrel did not come tapped for a standard FSB, and I am using an Adams Arms kit with mine. Switching to DI would obviously be more difficult since I am restricted to finding a bolt-on gas block or having to have someone tap it for a standard front sight. If you do a conversion, you obviously don't have this issue. There are supposed to be a couple of good piston conversion kits out there, with Adams Arms and Osprey getting a lot of praise. Just keep the old parts, and you are good.

You can also buy some Adams Arms spare parts just in case they break or you lose them.

[Creeky73]

very true. Some of the parts (gas block in particular) are quite pricey and make little sense to buy outside of the kit, but the parts you are more likely to have trouble with are affordable. The kits are $279 and it feels like a steal when you see the quality of the parts. I really wish I would have bought a complete BCM upper and just added the kit instead of building the upper altogether. Recently BCM has been running sales with their uppers at $375, tack on the piston kit and and a decent lower and you have a pretty formidable weapon for less than just about any factory piston setup you will find. Maybe RRA or Spikes (if they are building piston guns, I am not sure) will get that cheap but given my druthers I would take BCM over those two.

[Stocks]

Many of the guys I work with qualify with and carry Gas piston rifles. They perform flawlessly. There is no staked gas key which is nice. They shoot super clean! Gas piston has already been proven for years on M-14's, H&K's, FN FAL, and so many other rifles. I do not believe people are correct when they say the gas piston rifle is a problem waiting to happen or a p[roblem looking for a solution. Gas piston has always been a proven system. Runs super clean and there is little to no carbon fouling.

[AR-10]

The M14 and FAL were both designed as piston rifles from the ground up.

That's why they have railed receiver bores.

The round receiver bore in an AR upper is not a good choice for an operating system that uses an off-center pushrod to initiate the action.

In a direct impingement gun, the bolt carrier gets thrown backwards on it's center axis...the way it was designed.

[rob_s]

The M14 and FAL were both designed as piston rifles from the ground up.

That's why they have railed receiver bores.

The round receiver bore in an AR upper is not a good choice for an operating system that uses an off-center pushrod to initiate the action.

In a direct impingement gun, the bolt carrier gets thrown backwards on it's center axis...the way it was designed.

Bingo.

Piston in an AR is like a turd in a punchbowl. One guy thought it was a good idea to put it there and everyone else was disgusted. ;)

If you want a piston then get a piston gun. SCAR, ACR, XCR, etc. There is no real-world advantage to a piston-operated AR and there are more than a few downsides. Every piston myth has been debunked one way or the other at this point, and none of the downsides have been resolved. What we are left with is people that bought the hype, bought the gun, and refuse to see the forest for the trees. I have no problem with people buying them, it's not my money and it's not my gun, but I have yet to see a logical explanation for them that stands up to any kind of scrutiny and instead see a whole lot of snake-oil and backwards rationalizing.

[Specialized Armament]

The M14 and FAL were both designed as piston rifles from the ground up.

That's why they have railed receiver bores.

The round receiver bore in an AR upper is not a good choice for an operating system that uses an off-center pushrod to initiate the action.

In a direct impingement gun, the bolt carrier gets thrown backwards on it's center axis...the way it was designed.


Bingo.

Piston in an AR is like a turd in a punchbowl. One guy thought it was a good idea to put it there and everyone else was disgusted. ;)

If you want a piston then get a piston gun. SCAR, ACR, XCR, etc. There is no real-world advantage to a piston-operated AR and there are more than a few downsides. Every piston myth has been debunked one way or the other at this point, and none of the downsides have been resolved. What we are left with is people that bought the hype, bought the gun, and refuse to see the forest for the trees. I have no problem with people buying them, it's not my money and it's not my gun, but I have yet to see a logical explanation for them that stands up to any kind of scrutiny and instead see a whole lot of snake-oil and backwards rationalizing.

Stocks, commit these two posts to memory and don't make the same mistake once.

[Paulo_Santos]

Love my turd in a punchbowl. At least my turd has manners and doesn't shit where it eats. LOL.

I'd rather take a few seconds to clean the piston area than the whole upper. Never understood why all of the hatred. It is still an AR, with a different operating system.

[AR-10]

Hey now, I'm not hating on pistons. I actually get to shoot my bud's LWRC pretty often and I love it.

It's noticeably heavier than my M4, probably because the barrel is thicker, it's 1.5" longer, and the piston and op rod parts don't help in that regard.

I can also feel a difference in the perceived recoil. His 16" LWRC feels "snappier" than my carbine with an H buffer.

Is that a bad thing? Not really. Is it fun to shoot? Hell yes!!!

[Quib]

I can also feel a difference in the perceived recoil. His 16" LWRC feels "snappier" than my carbine with an H buffer.

Is that a bad thing? Not really. Is it fun to shoot? Hell yes!!!

The difference in recoil between the two systems was something I noted in my review of the Spike's Piston Upper.

From my review......


Having heard of the difference in felt recoil between gas impingement and piston driven weapons, I wasn’t quite sure what to expect for recoil. I was surprised at the first trigger pull. The difference in recoil between the two systems was slightly noticeable, but nothing like I had envisioned. While the gas impingement system seems to have a slower more steady “push” for recoil, the piston driven system seems to have a slight “kick” to it. Nothing negative by any means, but as I mentioned above, there is a slight difference noticeable to those of us used to the familiar recoil of the original design.

[Paulo_Santos]

The recoil in a piston is similar to a DI. My co-workers and I recently went to the range to zero their new AR's (Colt and a Bushmaster). After they shot my LMT, they both asked me why mine shoots like a .22. I then swapped out my lower with theirs and they noticed the difference right away with the Superior Shooting Spring. Plus mine has the FSC556 while they have the A2. As long as they are both gassed properly, both systems shoot very similar.

[Quib]

The Spike's upper in my review was mated with my carbine lower which consisted of a standard carbine buffer spring and the included Spike's ST-T2 buffer. There was definitely a noticeable difference in recoil. Not much like I said, but it was there.

I contribute the difference in felt recoil due to the difference in how each system operates. As I stated, the DI system in my opinion has more of a gradual “push” to its recoil.

With DI, we deal with gas pressure up until the gas reaches the bolt, where at that time the energy of the gas is converted to mechanical energy to operate the system. Very limited mechanical interaction or motion with DI, and the majority of this motion is linear.

The piston system converts its gas energy to mechanical energy right at the FSB. From the FSB back, now we are dealing with mechanical motion to operate the system, and this interaction of mechanical parts is where I believe the difference in recoil lays. Also, we loose the linear motion the DI system offers. Now we have introduced into the system, portions where this mechanical energy wants to naturally change direction (the piston op rod acting upon the bolt carrier) and this I believe is where the difference in recoil is felt.

My opinion, from a mechanical perspective. If I’m wrong, I stand corrected.

[Paulo_Santos]

You are correct Quib. The Short stroke Piston Systems are a little snappier due to the design. The recoil is a little different like you said.

[TripleBravo]

The DI v. Piston debate rages on and on, and I don’t think that many people on one side will ever switch to the other no matter how much is written and said on behalf of either operating system.

Throughout it all, I try to view them as two completely different weapon systems that happen to have controls in common. That is, I compare piston rifles to piston rifles and DI rifles to DI rifles. This way I don’t get caught up in the if-you-had-to-choose-between-one-or-the-other debate. It’s simply not an issue for me because I own several of both. The real debate is: Which piston rifle is the best piston rifle; and which DI rifle is the best DI rifle.

For someone just entering the world of the AR platform, my recommendation is always buy a DI rifle first. For a person who is going to only ever own just one AR platform rifle, they should have the original design. In my experience however, there are very few people that own only one AR platform rifle these days. Those that do don’t log a bunch of hours in forums like WeVo researching the heck out of their one rifle.

So for those of us that own several ARs, it’s really a matter of finding your favorite rifle…that rifle you choose out of your collection to shoot more than the others. For some of us it’s a piston rifle and for some it’s a DI rifle. In my opinion, the choice we make has as more to do about who we are individually than with which operating system is better.

Some of us hate to clean our rifles and will look for anything that prolongs the time before that chore must be tackled. Others love the peace found in taking the time to disassemble, clean, and lube our favorite weapons. Some of us like the simplicity of the DI design; while some of us admire the ingenuity of piston system engineering.

Because of the polar opposite nature of the issues brought up in the debate (ie clean v. dirty and simple v. complicated), it is unlikely that any opinions will change during discussions about piston v. DI.

All that said, for the absolute going into battle rifle, I pick the DI rifle every time…

[chrish03]

I love the Gas Piston Operating system in P.O.F. P415 18" MRR. I never have to clean it and I get nothing but positive comments at the range. POF is truly operating in a class of their own. I have shot rifles that would be considered POF's competitors and the POF (not just because I own one) has always been the top performer, most aesthetically innovative and unique, and flawless in its accuracy. I think the LWRC rifles are over priced, and lack any features that make it stand out among other AR's. The POF runs amazingly smoother, faster, and with less recoil than my standard AR15 Gas Impingement system in my Vltor MUR Upper. I went from a C3 Defense Billet upper/lower to a Vltor MUR upper/ POF Lower because I feel those two companies are at the top of the list for AR15 components and weapon systems.

How do I simply attach images from my own desktop (not a photo posted on photobcket or Flckr)??