AR: Direct Impingement or Gas Piston?

AR: Direct Impingement or Gas Piston???

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Some of you guys sure do get testy when people don't agree with you. You'd think someone had called your wife ugly or something.
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The only thing I get testy about sometimes is the continued perpetuation of the myth that DI ARs are not reliable.
I don't object to the existence of a kit or to other people spending their money on one. Anything to keep people buying domestic ARs and not imported AKs. :cool:
Every new trinket developed for the gun market is something productive for people to spend their money on besides hookers and blow... (or beer and cigarettes) :D
 
DI does not need any more cleaning than any other weapon in the inventory of the US Armed Forces. In fact it requires less maintenance than any of our machine guns, many of which use a piston in their gas system. Those of us that have actually used the rifle overseas can attest to its reliability even in 14.5" barrel format.
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I'm not sure what to say about this, other than no.
 
It certainly is one of the most overplayed myths out there. DI has worked for me but I've never been in a situation where it had to work. Maybe I get the luxury of cleaning my rifle more than some people but it has never been a problem for me. I have gotten some pistons ungodly dirty though and never had a problem. Maybe I'm just lucky but the DI has worked good and with minimal though not nonexistent upkeep they seem to hum right along.
 
Throw a bunch of sand in the lugs or bolt carrier group of an AR-15 -- DI or piston -- and it's not going to run real good. That has nothing to do with the gas system and everything to do with the basic design and clearances of the rifle.

A properly-built DI AR-15 will not self-foul with carbon enough to cause failures.

-z
 
It seems to me that as long as you have quality parts and everything is put together right, it doesn't really matter. Yes, the DI system tends to make the bolt-carrier lubrication dry up faster than it would otherwise, and gets carbon in there, but as Zak mentioned, carbon in the bolt carrier is probably not the AR's main weak point; it is those itty bitty clearances in the locking lugs and between the bolt carrier and the receiver, and the relatively delicate/finicky magazines.

Merely replacing the DI gas tube with a small piston still leaves you with a short-stroke, relatively-low-impulse system with tight clearances.

IIRC, the piston HK416 did a little bit better than the standard DI M4 in those fine-sand tests the Army ran a while back, but not much better, and that the main cause of failures for both guns was probably sand in the magazines and around the bolt carrier.
 
I voted for gas piston since I just bought one! :D HOWEVER, I've never had a problem with DI but then again, I tend to shoot fifty rounds at the most (usually less) and then clean everything. I have a friend that has shot more than 4000 rounds through his AR in competition without ANY cleaning other than minimal lubrication of the carrier and bolt. In theory, a gas piston upper should run cleaner and cooler ... we should all be able to agree on that. Whether or not that makes a damn bit of difference to anything in the real world is up for grabs. I bought one because I wanted one and that's all the justification I need. The POF gas piston is designed to run dry i.e. no lubrication whatsoever. If you oil the piston, you may well end up forming a gummy mess so basically do what the manual says. Oh yeah, make sure you have a spare bolt since the Stag bolt that ships with the POF upper may not work!!

:)
 
If money were no object, I'd buy a DI that was top-of-the-line, with no corners cut. a Top quality take on the ARs original design (read: DI) would be cool to have, in my book. Because while my slightly-less-than-top-of-the-line AR has performed as well/better than the AK I owned (it's performed well, regardless)--I'm always up for sweetening the deal ;)
 
To be honest, I don't clean my rifles every time I shoot them. That would be no fun, and that's the main reason I have them.

While I "trust" my AK more than my AR carbines, neither have had numerous catastrophic failures. I likely "trust" my AK more because people on the internet told me I should, not because it is actually more reliable. Nevertheless, "trust" isn't a very useful concept when actual results and demonstration is available as a substitute.
 
Could you give some examples of "a DI that was top-of-the-line, with no corners cut"?
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MSTN or Noveske are two such makers.

My 3-Gun competition rifles were made by MSTN. My SBR training carbine was made by Noveske.
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All will run many thousands of rounds without cleaning - I haven't cleaned them in over a year each. They generally do not put a lot of carbon back in the receiver. They also all run dry.
 
I voted DI. I have 5 or 6 thousand rounds through my cheap-*** Bushmaster with NO failures of any kind. If money was no object, I'd just get a nicer DI. (I'm partial to Wilson Combat).

and I recently switched to MagPul P-Mags. tacticool factor, I like the windows in the side, I really like the dust covers that take pressure off the feed lips, and some of the tests I saw them survive were impressive.
 
If you are living on the ground, subject to the outdoors weather, firing thousands of rounds regularly, getting very little sleep for days at a time (or none at all), exhausted physically and mentally, and forgot to clean you weapon at all during this time you may see a problem when the time comes to use it.
For the average person who shoots at a range, goes to shooting courses, cleans regularly when shooting, or even lubricates on occasion, you wont see any problems with your DI rifle at all.
Personally Ive never seen a problem with DI rifles in combat in the desert, and havent heard of any modern DI rifles in combat having problems in the jungle either when maintained in the least bit.
 
Never saw a problem with the M16/M4s in the sandbox. I dont have problems with my AR except with Wolf steel cased ammo.
 
IMO piston uppers are pretty much like FLGRs for 1911s, a solution in search of a problem.

It's like routing the exhaust from your car back under the hood near the intake.
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That would be the EGR. Most cars since the mid 70s have it. Required emissions equipment.
 
The QUESTION is inherently flawed, and thus cannot be answered

If a rifle uses a G.P., then by definition, it's not an "AR". An AR, by definition, uses D.I. Thank you for your cooperation. I don't care what you name the GP guns - take your pick - but they're not a Eugene Stoner design AR15 type or AR10 type. :p

That's it I've had enough. I'm going to develop a DI retrofit kit for AK's.
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Now THAT's funny right there - I don't care who you are! :D
 
So how come no one (other than me in passing) has mentioned the heat issue. It's my understanding that one of the advantages of the gas piston system (in addition to being cleaner) is that the BCG runs a lot cooler lowering the chances of a "cook off". It's also my understanding that noise suppressors exaccerbate the heat issue. For all of us civilians that aren't involved in daily firefights, maybe gas piston uppers are a waste of money or unnecessary luxury, but how about someone in Iraq, Afghanistan etc, firing hundreds of rounds in a short period of time with a suppressor attached. Do gas piston uppers have a place (benefit) in that scenario? Surely, the design/manufacture of gas piston uppers (M4/AR) was driven by military rather than civilian needs.

:)
 
I see the DI in an automatic firearm like routing your exhaust through the engine block and transmission. What is the point to put two bad agents (heat and smoke/burned powder residue) in one if most sensitive areas of the rifle. Area that has to be kept clean, lubricated and as cool as possible.
Both this agents will mess the lubricating properties of your oil, and increase the forces required to run the thing smooth.
Ar15 was designed for DI so here the advantages between one or the other system is a bit harder to determin.

One can argue all day long, but puting damaging agents (residue and heat) in a lubricated mechanism is a bad thing, being it a rifle, engine or any other complex mechanism.
 
I voted piston, ONLY because money isn't an issue in this particular scenario. But in the real world, it doesn't make a difference. You'll never see me with a piston AR.
 
That would be the EGR. Most cars since the mid 70s have it. Required emissions equipment.
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THis wasn't introduced as a natural part of the engine. It was introduced to lower the emission. THe direct result of it was increase in engine temperature, shortened engine life, reduced power and increase in fuel consumption. So even there was and stil is a bad thing.:D
 
I only have a few 1000 rounds through my RRA middy but mostly from a couple carbine classes. I guess I'm trying to say DI works fine for me
 
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