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Old June 13, 2013, 12:35 AM   #1
iGunny40
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Gas piston Vs Direct Impingement?

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 ...
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Old June 13, 2013, 01:01 AM   #2
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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...
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Old June 13, 2013, 01:26 AM   #3
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Re: Gas piston Vs Direct Impingement?

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.
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Old June 13, 2013, 02:11 AM   #4
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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.
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Old June 13, 2013, 02:52 AM   #5
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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 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?
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Old June 13, 2013, 03:28 AM   #6
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Quote:
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.
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Old June 13, 2013, 04:49 AM   #7
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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 Nobody report me please, and thank you!
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Old June 13, 2013, 04:51 AM   #8
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Oh yeah, and at the time I made the username I was watching Gunnery sergeant r Lee ermey!
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Old June 13, 2013, 07:31 AM   #9
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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.
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Old June 13, 2013, 09:17 AM   #10
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Thanks for the Info man and thanks for not Judging, another Great thing about Gun forums
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Old June 13, 2013, 09:19 AM   #11
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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.
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Old June 13, 2013, 09:22 AM   #12
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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.
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Old June 13, 2013, 09:26 AM   #13
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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.
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Old June 13, 2013, 09:52 AM   #14
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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.
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Old June 13, 2013, 11:52 AM   #15
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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.

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Old June 13, 2013, 11:55 AM   #16
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I always wanted to see an AR18 in person. I have never had the chance..
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Old June 13, 2013, 12:06 PM   #17
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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.
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Old June 13, 2013, 12:24 PM   #18
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Quote:
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.
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Old June 13, 2013, 12:38 PM   #19
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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)
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Old June 13, 2013, 12:57 PM   #20
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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.
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Old June 13, 2013, 01:11 PM   #21
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piston

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!
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Old June 13, 2013, 01:40 PM   #22
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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.
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Old June 13, 2013, 03:07 PM   #23
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Thanks for all the replies, definitely gave me something to think about.
ALOT! lol
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Old June 13, 2013, 05:12 PM   #24
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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.
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Old June 13, 2013, 05:46 PM   #25
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Sam, they were referring to the piston kit for ARs WRT development. Nobody is talking about piston in terms of those rifles.
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