View Full Version : Gas piston Vs Direct Impingement?
iGunny40
June 13, 2013, 12:35 AM
What Is the difference Is Gas piston Ar-15's and Direct Impingement? Which one Is more reliable In you're opinion? Sorry for the dumb question, I am new to Ar-15's.
In person lol ... :rolleyes:
Nathan
June 13, 2013, 01:01 AM
Putting your post into google would be the quickest way to get this answered. DI works. Piston is probably better in theory, but not completely developed...
allaroundhunter
June 13, 2013, 01:26 AM
I have put more than 10,000 rounds through my (DI) AR in the past 3 months without a failure... That means that in total that gun has upwards of 15,000 trouble free rounds through it. I'm not sure how reliable you want.
Right now, DI is cheaper than piston. As Nathan said, the piston operation hasn't exactly caught too much steam and is still fairly expensive.
In theory, the piston will run cleaner (which it does) and will therefore be more reliable. The DI system uses gas from the last shot fired to cycle the action and that causes more residue to be left in the action and entire receiver. If the gun isn't properly maintained (cleaned after each range trip or large volume of fire) then yes, it can cause a problem.
I, personally, clean each of my weapons religiously so there is mot a drawback for me using a DI gun.
Bacteriophage
June 13, 2013, 02:11 AM
Supposedly DI is slightly more accurate and piston is more reliable. Realistically, the difference either way is negligible for 99.9% of shooters. Only if you need to use your gun after immersion in water or dragging it through the mud is the piston likely to make a real difference in reliability, and only if you're shooting ultra-precise long-range competition is the theoretical accuracy difference of a DI going to matter.
Realistically, piston actions keep the bolt assembly cooler so you're less likely to burn yourself on it if you shoot a lot, but pistons weigh a few ounces more and cost significantly more.
iGunny40
June 13, 2013, 02:52 AM
How do i know if i'm in a LGS?
Do I Just ask him, "hey Is that ar piston driven or direct impingement"?
Just Joking :p I will look at some different ar's online and figure out what they are and what I want before going in. I had you though didn't I?
Theohazard
June 13, 2013, 03:28 AM
I am new to Ar-15's.
With a name like "iGunny40" I figured you must be in the Marine Corps or a Marine Corps veteran. The M16/M4/AR-15 should be very familiar to you.
iGunny40
June 13, 2013, 04:49 AM
I know people personally who have been In the Military, I have not. I Joined this sight to learn about Guns, and teach some things to other people I have learned. I am 15 years old and am very responsible with Guns, I picked the username I picked because It's short (less Typing) It was available and I "Technically" Own a Glock 27 In .40 caliber (Hence the 40 In my username)... before anybody gets "Troubled" Just know some people may be at home alone who are teenagers and may need a weapon to defend theirself If their parents are not home, and that said person has nowhere to go when their parents leave to Go to work (ect) also know not every person who goes to school Is In public school. I Know Im not crazy, I have a good life, my parents also know that and are confident in me being able to protect myself and being able to come up with educated theories of what I should do If a situation shall occur. I will not shoot unless I am about to be killed or I am being killed, I will use other means before that. Should I make a post about this? LOL :confused: Nobody report me please, and thank you!
iGunny40
June 13, 2013, 04:51 AM
Oh yeah, and at the time I made the username I was watching Gunnery sergeant r Lee ermey! :D
CharlieDeltaJuliet
June 13, 2013, 07:31 AM
Well it depends. Most companies make a reliable DI gun. There are only a few that make a reliable piston gun...ie LWRC,HK..etc. I have the Hk MR556, it is the most accurate (under 20") I have ever shot. Run some Blackhills through it and it is sub MOA. On the other hand I had an AR with an FN barrel and it shot almost as close groups. I have a RRA 24" Varmint that will blow both out of the water.
DI does work. The only time (IMHO) that a piston driven is better is in very fine sand or water. Both are great creations. But admittedly,they created a fix for a very minute problem with the piston gun. From my experience the piston guns are cleaner and require less lube to run. But they usually come with a price that that would allow you to buy a DI gun and a lifetime supply of moly-slide or other lube...
The difference is the DI uses a tube that pushes gas from the bullet leaving the barrel back to the bolt and forces it back to load another round. The piston guns, the gas moves a piston and the piston moves the bolt. It keeps some of the hot gasses out of the chamber.
IGunny40, I won't judge your situation. My father bought me my first pistol at 16. He only bought me my own because I was wearing his out..lol. I shot rifles at 6 y/o. My parents taught me responsibility and during my summer vacation, I worked for my dad to buy a brick of .22's each week. I spent my evenings shooting in my backyard.
iGunny40
June 13, 2013, 09:17 AM
Thanks for the Info man and thanks for not Judging, another Great thing about Gun forums :)
Slamfire
June 13, 2013, 09:19 AM
I am occasionally squadded with a Law Enforcement Officer who is also an Army Reserve Rifle Team Shooter and a veteran of Iraq/Afghanistan. He has fired many rounds in combat, and had many rounds fired at him. His personal choice of AR15 is gas piston. That is what he bought for himself. He told me, it is because gas piston keeps the mechanism cleaner. I think all other considerations are a wash.
For a target rifle the direct impingement gas system provides a more accurate mechanism due to less moving parts. But, as my Bud and myself discussed in the pits, when rounds are incoming, keeping that heart rate down is pretty difficult.
allaroundhunter
June 13, 2013, 09:22 AM
The easiest way to tell is by looking at the gas block.
However, when you see AR prices get closer to the $1,750, you can start asking if it is a piston gun.
tahunua001
June 13, 2013, 09:26 AM
in AR15s, the DI rifles are more reliable. they were never designed with a piston in the first place. the gas piston AR15 was the answer to a question that was never asked. people didn't like having to clean their AR15s every several hundred rounds so they started slapping on AK47 style pistons onto their ARs so that they didn't foul with burnt powder as quickly.
this type of arrangement is not such a bad idea for military rifles but it's horrible for civilian application as a piston requires a very specific amount of pressure from the fired projectile to actuate it. since the military only uses 2 or 3 different loads in any given caliber and most are within very close proximity to each other(pressure wise). this is not a problem. however with civilian use there are dozens of different factory loads on top of the infinite number of hand load possibilities. if the pressure is too far out of spec your piston will no operate and you will effectively have a bolt action AR15 requiring you to operate the bolt manually. many civilian piston kits nowadays have adjustable gas systems to compensate for this but you have to keep a log of what setting works best with which ammo and the first several shots out of any new brand are going to be trial and error, trying to find a setting that functions properly.
me? I can live with cleaning every few thousand rounds... my gun never jams and It's never been cleaned in the 4 years I've owned it.
CharlieDeltaJuliet
June 13, 2013, 09:52 AM
See, I am going to have to disagree there tahunua001. I will put my Hk against any DI gun for reliability. I promise eight out of ten times you will have to clean yours first. As far as specific pressures, the Hk has a self regulating gas block. It has never failed to fire any round, including low powder sub sonic loads or any hand load I have used. While reliability may be an issue for some piston manufactures or piston conversions, an LWRC or Hk are very reliable, I will even say more so under certain conditions.
James K
June 13, 2013, 11:52 AM
The original "piston type" AR was the AR18/AR180 (the latter is the semi-auto version). It might well have been a better rifle than the AR15/M16, but the Army had already adopted the M16 and the AR18 never was fully developed.
It certainly would have been less expensive and easier to manufacture than the M16, being made from steel stampings, and is far less affected by dirt or sand than the M16.
Jim
CharlieDeltaJuliet
June 13, 2013, 11:55 AM
I always wanted to see an AR18 in person. I have never had the chance..
Slopemeno
June 13, 2013, 12:06 PM
I've shot a couple of Armalites- Both Sterling and Howa's. I'll take a DI AR.
I've shot stock M-16's/XM-177's doing mag dump after full auto mag dump- that rifle is as reliable a rifle as you'll find- dirty or not. Lube it.
Theohazard
June 13, 2013, 12:24 PM
iGunny40 posted
I am 15 years old
Having been in the Marine Corps, I took from your username that you were too. A Gunny (Gunnery Sergeant) is arguably the most revered rank in the Marine Corps; a name like "iGunny40" will look to many people on this forum like you're representing yourself as being a Gunny. I'm sure it wasn't your intent to misrepresent yourself and I'm also sure you meant no disrespect from it, but this is just a heads up; Marines hold the rank of Gunny in very high regard and I'm sure this won't be the last time someone mistakes you for one based on your username.
As for the DI vs gas piston debate, I'm mostly a DI guy myself. In my opinion, the drawbacks of a gas piston design are only worth it if you don't like cleaning very much, if you mostly run suppressed (though short-stroke piston designs tend to be louder with a suppressor than long-stoke piston or DI designs), if you're in 12-hour firefights, or you're using your weapon as a light machine gun. I prefer the accuracy, simplicity, parts interchangeability, and lower weight of a DI design. Even when I was in the Marine Corps infantry I didn't see the DI design as a drawback; it takes no time at all to pop the bolt out, quickly wipe everything down, CLP it up, and throw it back together.
RC20
June 13, 2013, 12:38 PM
DI is fine for civilian use.
Theoretically the DI is more accurate as its true free floating.
Reality is that the accuracy of the AR is way overhyped. With match grade rounds the DI would likely be better, but average ammo, no.
The army found out how to keep the DI working in the worst environment, not a great way to go but when you are stuck with it, you either make it work or you change it.
You will note that the Marines are doing an underhanded shift to the Piston system MK27, and they went with piston on the HIK416 and 417.
Keep in mind, those guns were deigned with it from ground up and will fit into an AR lower (sans some of the intentional fit offset by the ones make in Germany).
An upper AR with a piston that has been modified is not the best setup, but again its not going to see the kind of engagement the military does and probably works fine for civilian use if its made by one of the better AR mfgs (RRA, Stag if they made one, S&W, Rugger, i.e. companies that will be there and better yet, the ones that stand behind their products)
Hard to beat the simplicity of the DI.
And keep in mind, most pistons are actually gas tappet/short stroke piston systems. They are not the long stoke direct drive of the AK and Garand actions.
Robinson Arms XCR is an example of a great system that does an extremely good job of bring the AK system fully up to date and the best ergonomics in controls of any carbine I have shot or handled, but their customer support is always on life support. They would be an example of who not to buy from as they could be gone any day and stagger along.
If I was going to switch he military to a piston, thats what I would do, buy out RA and take over their pattens (send Alex to an Island someplace with a machine shop and let him play by himself, grin)
CharlieDeltaJuliet
June 13, 2013, 12:57 PM
Make no mind that I want nothing to do with a AR15 piston kit. When I speak of reliability of the piston system I only mean Hk,LWRC... and a custom builder I know who only makes piston systems. This is from my experience and is my opinion from that experience. I will not include Ruger because I have yet to put one through the mill.
sam colt
June 13, 2013, 01:11 PM
Not completely developed? Garand-piston; m-14-piston; mini-14; piston. I own 3 ARs. 2 are DI and 1 is piston, all have been very reliable but the piston does run cleaner! :o
RickB
June 13, 2013, 01:40 PM
Piston ARs are like 1911s with external extractors; who designed it, who built it, is the company still in business, will they be in 10 years, etc?
Even if you could prove to me that the piston (any piston) is "better" than DI, I wouldn't give up the ability to service my rifle with widely available parts.
iGunny40
June 13, 2013, 03:07 PM
Thanks for all the replies, definitely gave me something to think about. :eek:
ALOT! lol
ThatBeardedGuy
June 13, 2013, 05:12 PM
I've only ever shot DI-based AR-pattern rifles. Never had any issues with the gas system. Spending more on a piston-driven rifle because you don't want to clean it is pretty lazy to me, but that's just my opinion.
That aside, both of my ARs and my issued M4 never spontaneously combusted if I missed a cleaning. I think the issues with DI are way overblown. I'll try to find an article by a former SF soldier who ran something like 10,000 rounds through a DI rifle bone-dry and it worked fine.
globemaster3
June 13, 2013, 05:46 PM
Sam, they were referring to the piston kit for ARs WRT development. Nobody is talking about piston in terms of those rifles.
CharlieDeltaJuliet
June 13, 2013, 06:19 PM
It isn't because of cleaning. It is because of less wear and less lube needed to run them. This is why "this method virtually eliminates malfunctions common to direct impingement gas systems since hot carbon fouling and waste gases do not enter the receiver area. The rifle stays cleaner, reducing heat transfer to the bolt and bolt carrier, and drastically reducing wear and tear on other critical components. The service life of all parts is increased substantially"
That is from their brochure. I have fired the 416, ran 3-30 rounders through it and was handed the bolt. It was not hot nor even remotely warm. When they ran over 20,000 rounds (full auto in one weekend) through a 416 without a hiccup. It still was shooting well within military accuracy specs... The life span of the rifle is 3-4 times the standard M4. They are more forgiving in sand water and dirt. That is why the Navy seals use them. That is why the marines are replacing part of the M249's with them...
kraigwy
June 13, 2013, 06:30 PM
DI is fine for civilian use.
OR
If you were crawling around the jungle, dragging it through rice paddies for months at a time it works great for the military also.
Bartholomew Roberts
June 13, 2013, 06:38 PM
If you search either TFL or the Internet, there are many good discussions on this. Most of the actual differences due to operating systems are overblown - for example, the 416 has a longer life because it is a modern firearm designed with modern materials as opposed to a modern carbine made from parts originally designed for a 20" rifle in 1960.
If you look at comparable rifles with a DI operating system (Knights Armament SR15E3 for example); but modern engineering and materials, they compare very well.
For example, there is a comparison between a Ruger SR556 piston and a Colt DI to evaluate the hot bolt issue. It comes down to a 40F difference after 5 consecutive mag dumps. It strikes me as unlikely that kind of difference is likely to have a functional effect.
Personally, I would go with a DI system (and the old 1960s parts) because the parts are plentiful, available, interchangeable, and there is a MASSIVE knowledge base on their operation. As much as I sometimes get interested in a new SR15 or a fancy piston - expensive proprietary parts do not excite me (although you can now get AR bolts in 9310 steel).
CharlieDeltaJuliet
June 13, 2013, 07:15 PM
That is why I precisely would not defend the Ruger as said earlier, I have no experience with them. The Hk is a considerable difference in temperature.
ThatBeardedGuy
June 13, 2013, 07:23 PM
I can't think of any instance where I'd need to fire a magazine and then pull the BCG, so that smacks of a gimmick to me.
I've literally never had an issue with DI-gassed weapons that wasn't related to a spring failure in the magazine. They simply don't cause issues for me.
tahunua001
June 13, 2013, 07:51 PM
See, I am going to have to disagree there tahunua001. I will put my Hk against any DI gun for reliability. I promise eight out of ten times you will have to clean yours first. As far as specific pressures, the Hk has a self regulating gas block. It has never failed to fire any round, including low powder sub sonic loads or any hand load I have used. While reliability may be an issue for some piston manufactures or piston conversions, an LWRC or Hk are very reliable, I will even say more so under certain conditions.
ok first of all, you are comparing a $3000+ H&K to a $1000 DPMS project rifle. that's like challenging a turbo'd Jetta to a race when you drive a Lamborgini Diablo.
secondly, I mentioned that Piston ARs do not foul as quickly as DI, so your assertion of being more reliable because I'll have to clean first just goes on to re-enforce my statement. however, give me a cleaning kit and I can keep my AR going just as long as you can keep yours(within reason).
CharlieDeltaJuliet
June 13, 2013, 07:58 PM
No tahunua001, I wasn't comparing to a DPMS, I will compare it to my DDV4. I disagree, I believe the piston system will last longer due to les heat transfer and fouling. The wear is less. The standard usage life of an M4 before re barreling and bolt etc.. from the government is 8-10k rounds. The 416 is almost 4x that. I will be the first to say, most people will never shoot an AR enough to tell the difference. The piston guns are a waste for most to spend the price of the Hk or LWRC. I just think IMHO from my experience with them, they are superior in almost every way except price.
Sorry tahunua001, I mean no disrespect, this is just my opinion.
ThatBeardedGuy
June 13, 2013, 07:59 PM
If I'm ever in a place where I have to shoot so many rounds that I'm literally required to stop and clean the weapon to keep firing, I should probably reconsider my life choices.
CharlieDeltaJuliet
June 13, 2013, 08:03 PM
Anywhere there is fine sand. It isn't even about rounds fired its about dependability in multiple conditions, and overall life span. The piston system handles sand, water or mud. I am not arguing semantics. I am stating my experiences with the two systems. I own 4 DI guns and love them. One of the is the most accurate AR I have ever owned(24" barrel). But I won't deny the piston system is better, if Hk, or LWRC.
ThatBeardedGuy
June 13, 2013, 08:06 PM
If you've got $3000 to drop on a rifle whose performance differences only start once you've fired about $20,000 of ammo through it, more power to you.
I've been in the military for six years and owned ARs for four and I haven't even come close to shooting that many rounds.
CharlieDeltaJuliet
June 13, 2013, 08:06 PM
Enough arguing, we each have our own opinion. I will stand by mine, you stand by yours and we will agree to disagree. I just tried to do the same as you and give the OP my experience with gas piston guns..
ThatBeardedGuy
June 13, 2013, 08:09 PM
And yeah, I've spent a little time in places with "fine sand". Granted, I wasn't doing any shooting, but it's not really hard to keep an M4 clean enough to fire.
I've run my ARs wet, bone-dry, and everywhere in between. Both were basic M&Ps. I can't make them stop working.
Sure, the piston system is probably a better gas system. But going off Tahunua's analogy, a Lambo is going to beat a Mustang all day long, but at the end of the day, my Mustang gets me to work and back just fine.
tahunua001
June 13, 2013, 08:10 PM
No tahunua001, I wasn't comparing to a DPMS
hmm... kindof sounds like you were.
I promise eight out of ten times you will have to clean yours first.
HK is also an exception to the rule. DD, AA, Ruger, Stag, all of the common suspects do not have self regulating gas systems and suffer greatly for it.
also, Milspec ARs are not the best in the first place. HK is quite possibly the highest quality mass produced AR on the market... a DPMS/Bushmaster/Remington M4 is not going to be in the same ball park. I wonder if you were to compare your HK to a Seekins precision or Larue tactical if the fight would be so one sided?
EDIT: I also added the modifyer, within reason. shooting 1000 rounds in 20 minutes is not what I would call reasonable use. I'm talking about 1 slow mag dump(say 2 seconds per shot) every 10 minutes or so.
ThatBeardedGuy
June 13, 2013, 08:11 PM
I'm not arguing. I'm pointing out for the benefit of all that DI is not the boogeyman of gas systems. It's really easy for everyone to form an opinion on this debate, and I really wish I could find the article where a former SF guy ran thousands of rounds through a bone-dry DI-gassed AR with no issues.
CharlieDeltaJuliet
June 13, 2013, 08:13 PM
Nothing wrong with an M&P, I own one and love it. I have seen a DD quit running, while a group was testing against a LWRC. The LWRC didn't cease, but they tortured them both the same. It took over 4k rounds dry with dirt and sand but, as I was saying I am not knocking your guns at all. Take no offense. I stated my experience with the two systems.
CharlieDeltaJuliet
June 13, 2013, 08:14 PM
I agree 100% tahunua001. But I still think the Hk can hold its own.... I agree though about mil-spec.
And TheBeardedGuy, I never said they were the boogeyman. They (DI guns) honestly are more dependable than most will ever need. I believe you about the SF guy. I have seen a Colt go over 50k rounds on all original equipment. There was a big write up about it. I shoot my DI guns as much as my Hk. It the past 12 years or so I have put over 25k rounds through AR's. I have around 4k through my Hk (ammo went up too much to replace as easy). As I was saying I just believe the Hk and LWRC are better AR's than DI AR's. Just my opinion.
buckhorn_cortez
June 13, 2013, 08:17 PM
I own both types. A Barrett REC7 (piston) and a Les Baer (DI).
The Barrett was designed as a piston gun and not a DI retro-fitted to be a piston system - I think that's an important point. The rifle was designed and built to be piston operated. The REC7 gas block/piston is self-cleaning, self-regulating and will shoot whatever level ammunition you put in it, if you run a supressor the gas block has a position to regulate the gas for the supressor. The piston system adds 3.8 oz weight to the rifle.
Buy whichever you can afford. You're probably safer buying a DI as you can find one that will work reliably for whatever price point fits your budget. Piston rifles are more expensive and you have to carefully look at them for design, operation, and features.
CharlieDeltaJuliet
June 13, 2013, 08:21 PM
Dang it Buckhorn_Cortez, I am dying to get my hands on the Barrett. I bet it is creaking sweet. Heard great things about them.
James K
June 13, 2013, 08:28 PM
Hi, Sam Colt,
I did not mean that gas piston system in general was not developed, I meant that the AR-18 was not a fully developed rifle. Its folding stock was not well designed and was a weakness, plus the failure to capture the bolt springs on the guide rods when the rifle was disassembled was not a good design; a direct copy of the M3A1 system would have been better. The AR-18 is easier to field strip and clean than the AR-15, and it has no spring in the butt stock to collect water or moisture. In addition, its guide rod bolt system, as opposed to the tight bolt and bolt carrier fit of the AR-15, allows plenty of room for dirt and gunk that would otherwise stop the rifle.
Overall, the rifle, I thought, was better than the AR-15, not only because of the piston system but because of the economy of manufacture and consequent cost savings. It could also be made in countries with a less developed manufacturing base, a benefit for U.S. allies who could manufacture their own rifles rather than having the U.S. supply them at a grand a pop.
Jim
ThatBeardedGuy
June 13, 2013, 08:30 PM
I'm sure the HK is a better AR than just about any AR I could reasonably see myself paying money for. I absolutely believe you when you say that HK makes a good AR. Of course they do. The Germans rarely ever misstep when it comes to firearms.
But again, when you consider price points, the HK is to ARs what Wilson Combat is to 1911s. It's the high-end, and I'd feel bad about abusing such an expensive rifle.
That being said, my next purchase will be a Tavor SAR 16.5" so I'm going piston-driven after all, in a way.
CharlieDeltaJuliet
June 13, 2013, 09:16 PM
You will enjoy the Tavor. It is a hell of a rifle. Enjoy..
CDJ
HKFan9
June 13, 2013, 09:57 PM
I have shot a HK MR556 (civi 416) and the Tavor next to my BCM HSP Jack Carbine... I still prefer my Jack.. and as my name will say... I am an HK fan boy.
Piston costs too much for what you really get out of it...which the only benefit is an extra 3 mins of your less that would usually be spent cleaning your DI system. Sorry but that's about it. They run cleaner.. but not as clean as some people make them out to believe. Also if you throw a suppressor on the gun.. it will run just as dirty as a DI system because the bolt will be unlocking while the can is still under pressure so you will get blow back down the barrel not just a gas tube.
The late great Noveske himself explained this in an older interview of why they toyed around with, but never felt the need to make a piston AR.
Buy what you like, but a piston isn't any more reliable than a DI.. just saves you some time cleaning.. if your time is worth the price difference.. or you just LIKE that particular AR... more power to you.
Have a pic of the Jack and the Tavor.... not the Hk however....
http://i299.photobucket.com/albums/mm312/HKFan9/photo1-2.jpg (http://s299.photobucket.com/user/HKFan9/media/photo1-2.jpg.html)
KyJim
June 13, 2013, 11:20 PM
Then there's the Daewoo K2 and derivatives. This is the rifle used by the South Korean Army. Many features, such as the bolt carrier group, are derived from the M16 and the gun uses the M16 magazines. However, it has a gas piston system derived from the AKs. It is somewhat similar in appearance to the AR18.
I bought the civilian version (AR-100) one back before they were banned in 1994. I haven't put a lot of rounds through it but I've never had any issues with it. The folding stock is pretty cool. http://en.wikipedia.org/wiki/Daewoo_Precision_Industries_K2
CharlieDeltaJuliet
June 14, 2013, 06:24 AM
I will leave you with this... and will let this horse die...
Larry Vickers said the following on M4C.net:
"Piston AR's have their place- to determine if you need one ask yourself four questions;
1) Do I need a barrel length shorter than 14.5 inches
2) Do I need to run my gun suppressed a lot
3) Do I need to shoot a lot of full auto
4) Do I need to shoot a wide variety of ammo
Piston guns have been shown to be superior in those four categories over a DI gun. If you can say no to all four questions a good DI gun will do you fine.
http://www.m4carbine.net/showthread.php?t=107613
Skans
June 14, 2013, 07:44 AM
Here's my take on the gas impingement vs. gas piston debate as it pertains to AR's. The AR was designed around gas impingement - it's a good design. Compact, lightweight, efficient design. It works well. Redesigning the AR to be gas piston is making it into something it was never intended to be. I have absolutely no interest in gas piston AR's and avoid them like the plague!
That doesn't mean I dislike all gas piston 5.56 rifles - there are some excelent ones out there. If I want a gas piston rifle, I would choose one that is not AR based and was designed from the start to work with a piston.
SR420
June 14, 2013, 09:21 AM
All of the DI ARs I've owned over the past few decades have been 100% reliable.
I switched to a piston driven AR only after adding a suppressor to my tool box.
The AR I chose was designed with a piston system from the ground up, not a kit.
BPowderkeg
June 14, 2013, 09:26 AM
very interesting !
I have put more than 10,000 rounds through my (DI) AR in the past 3 months without a failure... That means that in total that gun has upwards of 15,000 trouble free rounds through it.
how many cleanings ?
BPowderkeg
June 14, 2013, 09:34 AM
...not Judging, another Great thing about Gun forums
whoa.......!! you apparently have not been around gun forums much, i have been around internet gun forums for over 20 years and have found them to be very judgmental, hypocritical, dishonest, plus many other negative terms !! :eek:
enjoy.., but beware !! :D
allaroundhunter
June 14, 2013, 09:44 AM
very interesting !
how many cleanings ?
I have cleaned it about 5 times in the span that I have fired 10,000 rounds (solid cleanings). I have wiped the bolt down and given it some CLP about every 750 rounds.
.... And my barrel is getting pretty worn out as of late :(
CharlieDeltaJuliet
June 14, 2013, 11:41 AM
Here is an article that is a good read about the Hk.
UBL was killed with an op rod gun. What do you send "When you only care to send the very best"? - Dev Group (Or Delta or 24th STS, or Ground Branch, FBI HRT, TSA, etc) with HK416's. Built from he ground up to be the most reliable, combat rifle. While its competition in dependability would be the AK, it beats it hand down in accuracy. Heck even the California Swat that responded to the Santa Monica shooting were all decked out in them. It's not to spend more money, I assure you they choose them because they want the very best when their lives are on the line. Now I am not talking of Adams piston kits or any other that was designed to fit into a DI gun, but only about Hk. If I get on LWRC it would be even more long winded.. And I am tired..lol
http://soldiersystems.net/2013/03/30/canipe-correspondence-retiring-my-416/
Striker1
June 14, 2013, 12:38 PM
Here is an article that is a good read about the Hk.
UBL was killed with an op rod gun. What do you send "When you only care to send the very best"? - Dev Group (Or Delta or 24th STS, or Ground Branch, FBI HRT, TSA, etc) with HK416's. Built from he ground up to be the most reliable, combat rifle. While its competition in dependability would be the AK, it beats it hand down in accuracy. Heck even the California Swat that responded to the Santa Monica shooting were all decked out in them. It's not to spend more money, I assure you they choose them because they want the very best when their lives are on the line. Now I am not talking of Adams piston kits or any other that was designed to fit into a DI gun, but only about Hk. If I get on LWRC it would be even more long winded.. And I am tired..lol
I'll bet more bad guys have been put down with DI guns...just sayin' :p
CharlieDeltaJuliet
June 14, 2013, 12:41 PM
Given, and I guarantee the AK has the DI AR beat for that too, but considering the Hk has only been in operation for a few years.. We might have to wait and see. Don't forget the marines are getting the IAR M27...
ThatBeardedGuy
June 14, 2013, 12:45 PM
Also don't forget that the USMC watches Army weapons competitions closely, and piston-drive is not a requirement for the current round of contestants, IIRC.
CharlieDeltaJuliet
June 14, 2013, 01:20 PM
The M27 (modified 416) has already been chosen to replace about half of the M249's. When the government has hundreds of millions in the M4 and all of their replacement parts, I would not expect them to replace with something else. As I said before it isn't for everyone. IIRC the cost of a complete 416 to the government is $1100 which is almost 2x the cost of an M4( link to the m4 cost per rifle http://www.fas.org/man/dod-101/sys/land/m16.htm).That does not mean the 416 isn't superior. I trust Delta,and the SEALs, when they say it is a vast improvement and their weapons of choice. They are the best of the very best, and know what they need to do their job. They just don't have the budget woes an average soldie does.
CharlieDeltaJuliet
June 14, 2013, 01:34 PM
I am done with the argument, because that is what it has became. I was supplying facts and my experiences for the OP. I am not even going to check the thread because I am not trying to change anyone's minds. I am simply providing the piston side of the answer. I think myself and the few others that have shot and own the Hk or LWRC.. Can attest to the quality of the gun. I never pretended to know how your AR's run. All I can say is how mine runs. I also provided facts from tests, Hk, and one of the co-creators of the hk416 Larry Vickers.. Take care
CDJ
Bartholomew Roberts
June 14, 2013, 02:26 PM
That is why I precisely would not defend the Ruger as said earlier, I have no experience with them. The Hk is a considerable difference in temperature.
If that is in fact true (I haven't seen any data on it, so I would not know), I doubt the operating system is a major contributor to the difference. For example, the POF piston system runs much cooler than the DI; but it also uses a giant finned barrel nut that provides much of the cooling.
I believe the piston system will last longer due to les heat transfer and fouling. The wear is less. The standard usage life of an M4 before re barreling and bolt etc.. from the government is 8-10k rounds. The 416 is almost 4x that.
I guess I am missing how the operating system causes one rifle to have to be rebarrelled faster than a different rifle with a different operating system? Could you elaborate on that?
As to the bolt, the AR15 bolt is designed to be used in a 20" rifle under certain operating parameters. It was designed using 1960s metallurgy. We know that we can greatly enhance the life of the bolt simply by radiusing the lugs where they meet the bolt or by using higher quality metals like 9310 (or both). However, changing the bolt design means changing the barrel extension and tracking that part in existing inventories, so it won't happen. Changing the metal is an easier solution; but you have to overcome institutional inertia. The Knight's E3 bolt has run 20,000 rounds.
Frankly, I'll be interested to see how the HK416 survives in the military small arms maintenance system (which is the root of many of the current AR15 problems) and if it turns out to be as durable as the M16 once it gets treated like one on a consistent basis for 20 years. For that matter I'll bet you could shoot 4 M16s to death before you ever got one 416 back from H&K's service department. However, the HK416 isn't limited by the design of its bolt, barrel extension or metallurgy. The engineers were free to use what they could without having to worry about compatibility with the 20" M16 (except for magazines - and even that is arguable).
None of that has anything to do with the operating system though.
Also not buying the "But the SEALs and Delta use it!" argument. I know a SEAL who carried an M14 for years. He didn't like it better than the M16 or think it was a better rifle; he carried it because he did a lot of over-the-beach stuff and in that specific environment, the M14 was a better choice. And contrary to popular perception, he didn't have a Matrix-style arms room to choose from.
Quentin2
June 14, 2013, 02:36 PM
To me, the worst potential problems of the various piston AR designs are parts availability and quick repairs, especially over the long run. If your DI AR needs a part you have your choice of hundreds of vendors selling standard parts, and you can install them yourself or have a local gunsmith do it. If your Ruger piston AR (for example) breaks, you must get parts from Ruger, and they may not provide them to you - you likely will be told to send the rifle to them or an authorized service center, not you or your local gunsmith. And if a proprietary piston design is ever orphaned, well you'd better start scrounging for parts now...
And with so many piston designs out there it's fair to assume a shakeout of some kind where some designs will be abandoned. You could be stuck with Beta vs. VHS or HD-DVD vs. Blu-ray.
Quentin2
June 14, 2013, 02:47 PM
I see the advantages of Direct gas impingement as:
Lower cost, lower weight, standard parts available from multiple sources, simple, proven design that works well in many applications and with standard carbine and rifle length barrels
Piston designs, as has been pointed out earlier, may be better suited for certain tasks and AR designs but they aren't superior for the vast majority of AR applications.
buckhorn_cortez
June 14, 2013, 04:26 PM
Dang it Buckhorn_Cortez, I am dying to get my hands on the Barrett. I bet it is creaking sweet. Heard great things about them.
It is a nice rifle. Ronnie Barrett knows how to design rifles. I had a Colt AR in 1984 and it was a jamtastic machine because it did not have the M4 modifcations. I sold it in 1985 and didn't think about an AR until 2010.
Then I shot a friend's SIG, and started looking at piston ARs just to see what they were all about. I looked at and shot as many as I could, including SIG and HK. Then I saw a REC7.
It's hard to explain without seeing, handling, and operating the rifle. It is so well designed and manufactured. The fit and finish are like a Wilson - while the design and operation are totally Barrett. It works under all conditions with no extra help needed.
I cleaned it at 3,000 rounds to see what was going on with it. The barrel was fairly dirty and needed cleaning, but the bolt and inside of the receiver were nearly as clean as when it was new. I took the gas piston assembly apart (you flip a lever on the front of the gas block, tilt the gun barrel down and it falls out of the gas block).
I wiped the piston and inside of the gas block with SLIP Carbon Killer and the cleaning rag was faintly grey. After that, I became a believer that the piston system truly is self-cleaning.
The gun needs minimal lubrication as the bolt and carrier are NP3 coated. I have been using a very light coating of ProGold MFR-7. It's very nice to run the gun almost dry where I live (New Mexico) without needing to constantly lubricate the bolt. It never has a bolt covered in a mixture of gun gas/fouling munge + dust + oil :).
It is farily accurate as it will give slightly under 1 MOA accuracy running 55 grain bullets at 100 yards. The gun club I belong to has a 100 yard tunnel so you can test rifles without wind drift. I've done that with the REC7 on two ocassions with my sled and sand bags - and both times it shot 0.75 MOA.
It seems to be the rifle no one knows about (or thinks about) as I have never seen another one (although the FFL I purchased it from says he sells about 1-2 per week). I would recommend looking at the REC7 if you can find one. It is certainly one of the better options in piston operated ARs.
Bartholomew Roberts
June 15, 2013, 02:58 AM
In somewhat related news, the Army just cancelled the Improved Carbine program saying none of the submitted rifles met the minimum criteria for continuation. The contenders were FN FNAC (SCAR), HK 416A5, ACR, ADCOR Bear, Beretta ARX160 and Colt Enhanced M4. All contenders were piston designs.
The Army wanted to see 3,600 mean rounds between stoppage with M855A1. According to Army data, the current M4 does 1,691 MRBS with M855A1.
BPowderkeg
June 15, 2013, 09:15 AM
The contenders were FN FNAC (SCAR), HK 416A5, ACR, ADCOR Bear, Beretta ARX160 and Colt Enhanced M4. All contenders were piston designs.
they should have tried the LWRCI M6 originally designed by P. Leitner-Wise and a proven piston carbine, i have one of the originals and it functions flawlessly, is "man sized target" accurate to over 500 yds., it does have one flaw and that is the flat coil op rod return spring, when they break the gun still functions, just ask me, mine has broken two of them.
robertsig
June 15, 2013, 09:25 AM
this type of arrangement is not such a bad idea for military rifles but it's horrible for civilian application as a piston requires a very specific amount of pressure from the fired projectile to actuate it. ......
if the pressure is too far out of spec your piston will no operate and you will effectively have a bolt action AR15 requiring you to operate the bolt manually.
Baloney. Tell that to my PWS MK116.
ThatBeardedGuy
June 15, 2013, 01:42 PM
they should have tried the LWRCI M6 originally designed by P. Leitner-Wise and a proven piston carbine, i have one of the originals and it functions flawlessly, is "man sized target" accurate to over 500 yds., it does have one flaw and that is the flat coil op rod return spring, when they break the gun still functions, just ask me, mine has broken two of them.
Our rifles now are more than man-sized accurate to 500 yds. If your weapon has a known flaw, no matter how minor, the military probably won't be interested in it.
Bartholomew Roberts
June 15, 2013, 05:08 PM
they should have tried the LWRCI M6
The LWRC was submitted for Phase I of the competition but LWRC and a dozen other manufacturers pulled their entries because the Army wanted all rights to the TDP prior to advancing to phase 2. I bet those companies are glad they declined right about now.
jehu
June 17, 2013, 06:41 AM
Don't forget that the most widley used battle rifle in history,AK47, is a piston gun. I predict that one day soon DI will become obsolete when the piston operating system is perfected in the AR platform. I have two LWRC SPR's and 5 DI's.
BPowderkeg
June 17, 2013, 09:23 AM
allaroundhunter, what is the maker of your piston gun ?
BPowderkeg
June 17, 2013, 09:38 AM
everyone !
i have tried to find the specifics of every piston operating systems of every AR-15/M4 design and the only one i can find the specs on is this one,
http://www.leitner-wise.com/file/images/MOD1_prod_img.gif
not a very good view, but this design is in my OPINION one of the best piston systems yet !
all these piston makers that advertise in gun magazines tout their system but very few show their specific design, even when i go to their web site they do not show it specific parts LWRCI has a slide show of how theirs work.
Quentin2
June 17, 2013, 11:36 AM
Don't forget that the most widley used battle rifle in history,AK47, is a piston gun. I predict that one day soon DI will become obsolete when the piston operating system is perfected in the AR platform. I have two LWRC SPR's and 5 DI's.
"One day soon" ... You sure about that? :D
Boomer58cal
June 17, 2013, 12:04 PM
I don't get the range commando's. 10,000rds at the range is not the same as 10,000 rds in jungle nee deep in mud combat. In combat you don't just clean your gun every so many rounds. You clean it when you get a chance. You can't compare shooting the two under perfict conditions. Both DI and piston work great under those conditions. Piston gun works better in he!!.
My 0.02 Boomer
SR420
June 17, 2013, 12:09 PM
https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-frc1/576150_444882285528965_2092717469_n.jpg
Quentin2
June 17, 2013, 12:43 PM
Boomer, have you read the tale of "Filthy 14"! DIs can wallow in the filth for thousands of rounds. I've heard the round count went over 50k before EAG rebuilt the rifle.
http://www.slip2000.com/blog/s-w-a-t-magazine-filthy-14/
Boomer58cal
June 17, 2013, 05:40 PM
Oh I've heard many a story and don't get me wrong. I have 3 AR's that are DI and they're all reliable. A Colt AR15 in 223, a DPMS. 308 and a Rock river full match grade in with 26" bull barrel in. 308. As long as they are well lubed they run perfict. My SKS works clean, dirty, lubed or dry. If DI guns are 99% reliable than piston guns are probably 99.5%. Nothing is 100%. More reliable is more reliable. Even if it's only by a tiny amout.
My sks has to date has been 100% reliable. I can't say that about my AR's. They have all failed to do something at least once. I also have a 10/22 with close to 60,000 rounds through it( turned the first barrel into a smooth bore). The only time it's failed me was because of cheap ammo. Reliable is reliable.
Norhing wrong with DI guns. Infact they're probabilly better for the average person. If you're in combat that's differant. The reason M-4's are find for out military is that long supply train behind them. If your in a survival situation with no backup and no supply train piston is better. I've never even heard a of a guy dieing with a jammed AK in his hand. Have you? Probabilly not.
Boomer
Quentin2
June 17, 2013, 08:28 PM
Oh I've heard many a story and don't get me wrong. I have 3 AR's that are DI and they're all reliable. A Colt AR15 in 223, a DPMS. 308 and a Rock river full match grade in with 26" bull barrel in. 308. As long as they are well lubed they run perfict. My SKS works clean, dirty, lubed or dry. If DI guns are 99% reliable than piston guns are probably 99.5%. Nothing is 100%. More reliable is more reliable. Even if it's only by a tiny amout.
My sks has to date has been 100% reliable. I can't say that about my AR's. They have all failed to do something at least once. I also have a 10/22 with close to 60,000 rounds through it( turned the first barrel into a smooth bore). The only time it's failed me was because of cheap ammo. Reliable is reliable.
Norhing wrong with DI guns. Infact they're probabilly better for the average person. If you're in combat that's differant. The reason M-4's are find for out military is that long supply train behind them. If your in a survival situation with no backup and no supply train piston is better. I've never even heard a of a guy dieing with a jammed AK in his hand. Have you? Probabilly not.
Boomer
Well rounding off numbers from the Improved Carbine trials )piston vs. DI M4A1) then doing some simple calculator math, here's my quote from earlier today...
...the M4A1's 1 malfunction roughly every 1700 rounds is pretty darn reliable. Something like 99.94%. Increasing that to 1 malf in 3700 rounds raises reliability up to about 99.97%. I know that's just statistics but are we talking a significant increase in reliability? Or reaching the area of diminishing returns? ...
No doubt plenty of soldiers have died with a jammed AK at their side. Plenty of jams with any piston rifle too, M14, M1 Garand and others. I joined the Army in 1966 and was issued the M14 most of my three years. Except when I was sent to Vietnam with the M16. It worked if you took care of it and if you got good ammo and mags. It still works well today.
jehu
June 18, 2013, 09:33 AM
Thru out history new technologies and operating systems have been rejected by old stuburn hardheaded generals and others. The Henry rifle was rejected at first during the Civil War by the high command but after soldiers bought their own and found them to be very effective the US military finally fielded approx. 1700. Adolf Hitler refused to let production happen of the Sturmgewher until they finally put one in his hands to shoot but it was too late to make any differance in the out come of the war. Even the original DI M16 in Vietnam was a jamomatic until changes were made. Again I predict that the piston system in the AR platform will become the norm after some battle field use and tweeking that it might need.;)
Boomer58cal
June 18, 2013, 11:31 AM
I'll strongly agree we've reached the point of diminishing returns. All new tech thst pushes the limits will have teething issues like the M16 did. I'll take that 0.01% extra reliability every time if my lifes on the line. As a rule... I'll take accurate enough and dead reliable over 1/4 moa and works most of the time.
But that's just me. Boomer
Patriot86
June 18, 2013, 12:05 PM
This has been done to death but it boils down to:
Piston Guns:
Pros:
"Some" reliability improvements (arguable point)
Easier to clean
More suppressor friendly
Cons:
Heavier(though some high end models now weigh about as much as a DI gun)
Less Accurate(again, arguable point)
More expensive(some low end models now cost as much as a "mid range" AR)
Parts availability
DI Guns:
Pros:
Lighter
Cheaper(in general)
High level of parts availability
"More" accurate(arguable)
Cons:
More difficult to clean
"Less" reliable(again, very arguable)
I have both DI and Piston guns, this is my opinion let me start off by saying.
If I am going to buy an AR, it is going to be DI period. Parts are almost universally interchangable, parts are also very available. I like the balance of a DI AR-15 more than a Piston AR-15. A DI AR-15 I feel like I can balance it on one finger.
I like Piston guns, I really do. I also own a SIG-556 rifle which for those not in the know, is a civie version of what is often called "The Swiss AK-47".
If I am going to buy a Piston gun its going to be a "from the ground up" Piston design like the SIG-556, H&K 416 or SCAR 16/17.
I love my SIG-556 but it is front heavy like most Piston designs. Its super easy to clean but the sucker is heavy. I don't know that I would want to be lugging it around all day every day.
For what its worth with about 2000 rounds through each gun I have not had a single failure of any type period. One day I might play a game of sandbox with both and see what happens but call me crazy I don't like dropping my rifles in the sand for the heck of it.
Boomer58cal
June 18, 2013, 12:12 PM
Agreed. Beating a dead horse :p
Art Eatman
June 18, 2013, 09:56 PM
I have no doubt that somebody will come along and resurrect the poor old horse in order to beat on it once again.
Enough for now, for this, the umpteenth iteration of this subject. :)
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