[dprice3844444]

http://www.pof-usa.net/articles/P416Torture.pdf
http://atwar.blogs.nytimes.com/2010/01/12/m4-and-m4a1-guns/?h

check out the gun tests

[Nico Testosteros]

Chivers is a journalist who is actually qualified to write about firearms. I like his stuff.

[C-grunt]

I'm not a big fan of the piston guns as there is no set standard yet and everyone makes their own proprietary system. That being said the SWAT team on my dept uses POF rifles and they have held up very well with the high amount of rounds they put through them. They are a bit heavy though.

[Bartholomew Roberts]

Well if you compare two different rifles with two different operating systems, then any difference in performance must be a result of the operating system choice, right?

For example, just using the 5oz heavier M4A1 SOCOM barrel will let the M4 go from the 536 rounds seen in that test to 900+ rounds with no barrel burst (http://video.nytimes.com/video/2010/01/12/world/asia/1247466496261/m-4a1-firing-test.html) (though it does go bolt action around 911 IRRC). So almost twice the round count; but with no change in the operating system.

Not sure what the barrel profile of the P-416 is; but it does use a little bit bigger barrel nut than the M4 - one that the manufacturer claims dissipates heat 5 times faster and probably accounts for some of the weight difference C-Grunt noticed. If I had to guess, I am betting that played a larger role than the operating system.

http://www.thehighroad.org/attachment.php?attachmentid=164334&stc=1&d=1336763026

And naturally, all of this information is vital for when you have to dump 535 rounds ($214 worth of brass-cased FMJ ammo) downrange in less than 2 minutes. That happens all the time.

[d2wing]

After action report indicates they should maybe find a way to protect heavy guns from small arms fire rather than use small arms as heavy arms. In the first article what is being compared? How does a barrel failure or gas tube failure reflect on impingement system? According to the article, peak temps were lower in the M4. It proves the upper they used was more reliable than a standard M4 for full auto from a tripod.
Isn't that what machine guns are for?
I hear new trials are underway for improvements to the carbine. I'm all for improvements. Gimmicks not so much.

[Shadow 7D]

Um, yeah, what he said
I don't understand why you would sacrifice the SIMPLICITY of the DI system (even if it does require more cleaning - not I didn't say maintenance)

for a HEAVIER, more complicated system with more parts to break or just go wrong. What happens if you are over gassed from using plinking rounds or undergassed when you really need it.

[Robert]

I never though cleaning my AR was all that difficult. I no longer subscribe to the military standard of being able to eat off the chamber, but I get it clean. And it is not hard. At all. Even when I only clean it every few thousand rounds.

Piston guns are fine if that is what your want. It's your money, go nuts. To me it is a solution looking for a problem.

[carbine85]

I'm not a big fan of the piston guns as there is no set standard yet and everyone makes their own proprietary system
Agreed. This is the only real problem I see with the pistons. It makes sense to me that pistons are the next evolution of the AR platform and once a standard is set it will take off. I can't think of another system that has evolved like the the AR and most of the changes have worked out.

[jad0110]

I never though cleaning my AR was all that difficult. I no longer subscribe to the military standard of being able to eat off the chamber, but I get it clean. And it is not hard. At all. Even when I only clean it every few thousand rounds.

Piston guns are fine if that is what your want. It's your money, go nuts. To me it is a solution looking for a problem.

Same here. I spend at most about 10 minutes cleaning my AR (pull a boresnake through the barrel a couple times, wipe down the BCG and relube). Never had the slightest issue.

Most of the crap that ends up in the chamber comes out of the spent case itself anyway. So if your goal is to eliminate chamber fouling, switching to a piston system on an AR is like putting a bandaid on a broken leg. When shooting dirty surplus ammo (Wolf) in my AR, M-1, SKS or an AK I used to own, all four get/got crudded up about the same. The only difference I can discern is that the piston driven guns spread the crud over more parts. :)

[madcratebuilder]

Piston guns introduce problems not found with DI. Carrier tilt, RE wear issues need to be addressed. Proprietary parts is a major draw back. I'll keep my pistons where they belong, on Garand's, Carbine's and M14's.

[303tom]

(direct impingement) Less parts, Less to go wrong................

[jmorris]

Never had a problem keeping my "old school" ARs running but I can understand why companies want to have piles of piston uppers ready for sale. Just like the Pet Rock, how can you call a guy a fool that can sell rocks for $5 each.

[rugerdude]

I was once involved in a training exercise where I put 14 magazines through my M4A1 all on full auto in the course of something like 8 minutes. I did not experience any malfunctions and I developed a new respect for DI and a new skepticism about all the piston designs being that much better.

I like to think of acceptable reliability in terms of the rifle being able to fire (without a malfunction) the amount of ammo that I'm willing to carry on my person. Anything beyond that is great, but I won't pay more for something that I will not ever use just to say that I could if I needed to.

[Gtimothy]

I see I'm in the minority here. I've had Direct Impingement (DI) ARs and always hated how dirty they ran. The the gas tube makes the hand guard hot after a couple of magazines and the spent gas going into the BCG made the receiver hot too. I've noticed that several people here say cleaning a DI AR only takes a couple of minutes but I'm not sure what kind of minute they're talking about. I don't believe you have to make a gun "white glove" clean but even so it takes time to disassemble the BCG on an AR to clean it! DI BCGs get covered inside and out with spent gas residue.

When I fired my first piston AR, I was hooked! Yes there are more parts, (mine have 4 more than a DI gun), and the piston weighs more than a gas tube but IMO those are small issues! I'll take the extra few ounces of weight as a trade off for a cleaner, cooler running gun. Other people cry out "carrier tilt"... If I'm not mistaken, a piston gun and a DI gun exert pressure at the same point on the BC group, just differently. I haven't noticed any unusual wear on my piston guns, so I'll have to wait until I see something I don't see on a DI gun.

My piston guns run MUCH cooler too! I can fire 2 or 3 magazines through my ARs and the hand guard although warm up by the gas block, is cool to the touch everywhere else. The BC group is still pretty much "room temp" to the touch after firing as well. Don't try that with a DI system, you'll leave your finger tips burnt onto it! Also after I'm done shooting, the only real cleaning needed is the barrel and gas block. The BC group is still clean but you may want to use a Q-tip on the bolt face...no biggie. One other thing I like is, although the .223 doesn't have much in the way of recoil, my piston guns seem to have less felt recoil. All in all, I'll take my piston guns over the DI guns. Just my opinion...

[KennyFSU]

http://www.youtube.com/watch?v=unYAcHIUhXE&feature=youtube_gdata_player

DI seems to operate fine with A LITTLE water. ;)


Sent from my iPhone using Tapatalk

[SlamFire1]

DI makes for a fine target weapon but that red hot gas tube sure makes me wonder why we ever adopted DI for a service weapon.

The answer has to be politics.

[Ignition Override]

The NYT writer/author Chivers, who also wrote "The Gun" (about the AK and M-16's development) was an infantry officer in the US Marine Corps.

You might still be able to read short excerpts of "The Gun" on Amazon.

[happygeek]

You can buy 'The Gun' for $16 new or as little as $4.32 used (http://www.amazon.com/The-Gun-C-J-Chivers/dp/B004Q7E0YA/ref=sr_1_1?ie=UTF8&qid=1336939853&sr=8-1). IMO it's a pretty good book. It's not just about the AK either, it traces the development of the Maxim and other rapid fire infantry arms that preceded the AK.

Personally I don't see anything wrong with DI. It's anecdotal, but I once ran 3,000 rounds through a M4 in two days at work and only had 1 malfunction, and that one was clearly the mag's fault. My only complaint, if you can call it that, is cleaning out the inside of the bolt carrier afterwards.

[HavelockLEO]

I have both and run both pretty often. My favorite is my A2 clone, but I trust my life everyday to a piston conversion gun I built.
BC tilt is a non issue unless you go cheap and only switch out the gas key instead of the bolt carrier.
Persoanlly I've noticed no reliability issues, or displaced fouling issues in my piston gun. The only part I've changed out since the conversion is the extractor and extractor spring. My uppers no where near as dirty after a range session either.
But to each his own I guess.

[kwelz]

DI makes for a fine target weapon but that red hot gas tube sure makes me wonder why we ever adopted DI for a service weapon.

The answer has to be politics.

Huh? A red hot gas tube after hundreds of full auto rounds concerns you? DI was adopted because it is a better system for this gun. It works just great in a combat weapon.

I suggest a few of you look up the temperature differences between a DI piston and normal Piston design. It is very minor.

[sugarmaker]

In my limited experience in highpower matches, 75% of the alibi strings are M1A's. 90% of the guns on the line are AR-15's. To me, the math seems to be in favor of the DI system. I find it very tolerant of various ammo combinations compared to my piston guns.

[dprice3844444]

you have to remember,this was a torture test to cause castastrophic failure in the most extreme condition.the skinny barrel,due to excessive heat,caused the metal in the barrel to melt,therefore blowing out.same with the gas tube,.in an incredible situation like that,which we will never use one like these were abused in our lifetimes,we will never experience this problem.
it proved that in an severely extreme scenario,the gas piston and heavy barrel were the way to go.under normal conditions,we would not have that much ammo around and would be cycling/aiming alot slower,therefore,less heat buildup,less chance of malfunction.with the di system,as well as the other,it still comes down to weapons maintanance.

[valnar]

Not all piston AR's are the same. Check out the long-stroke system from PWS. It is different than the POF/LWRC/Adam's and other short-stroke systems out there.

[Bartholomew Roberts]

If I'm not mistaken, a piston gun and a DI gun exert pressure at the same point on the BC group, just differently.

You are mistaken. A piston exerts force above the line of the bore against the gas key. In DI the gas flows through the gas key to fill the space between the gas rings and the bolt carrier group, as the bolt carrier group is pushed backwards directly in line with the bore, the two holes on the side of the bolt carrier group pass aft of the gas rings and the excess gas is vented out the ejection port through those holes.

The reason this is an issue in ARs is because the bolt carrier was never designed to ride in rails to counter the off-axis force; because there was no off-axis force. So most gas-piston AR designs spend a lot of time figuring out how to counteract this problem; but still use AR receivers not designed for that.

The BC group is still pretty much "room temp" to the touch after firing as well. Don't try that with a DI system, you'll leave your finger tips burnt onto it!

There is around a 40deg difference in the bolt temperatur of a Colt M4 and Ruger SR556 after rapid firing 5 mags. (http://www.m4carbine.net/showthread.php?t=57400&highlight=sr556c). However, there is still another reason not to try shotgunning the bolt and dumping it in your bare hand immediately after multiple mag dumps - that whole "serves no practical purpose" thing.

it proved that in an severely extreme scenario,the gas piston and heavy barrel were the way to go.

Did it? It looks to me like it suggests that the P-416, which has a heavy fluted barrel (according to their website) and a 3.5oz barrel nut/heat sink handles heat better than an M4 on full auto. Though it is hard to compare directly since one is a magazine writer blasting away semi-scientifcally and the other is a professional testing lab conducting a test under controlled conditions. You seem to be assuming that the difference is due to the operating system rather than the extra barrel mass and heat sink/barrel nut. Why is that?

[Destructo6]

I've fired several full auto mag dumps through a piston HK 416 (10.4") and, sure enough, the bolt carrrier remained about room temp. However, the railed handguards were extremely hot. I don't know about you, but I usually hold the handguards when I shoot, not the bolt carrier. It was also quite a bit heavier than the 14.5" M4 with similar optics.

I've also fired many, many full auto mag dumps with DI M4s. Not always one, but often 3 or 4 mags through M4s with 15,000 rounds through them already. The handguards got a little warm, but not bad and I never thought about popping the bolt carrier out for a little feel.

You know, I didn't want to like the DI M4, but after putting untold numbers of rounds through them in all sorts of configurations, they work and they work well. They've won me over.

[crossrhodes]

All I can say to the nay sayers is read "Filthy 14". To many pros & cons for each system to say one is better then the other. I'm happy with my DI system.

[sansone]

seems to me the use of quality clean ammo negates the need for pistons

[Redlegvzv]

There is no getting away from the fact that the Bolt Carrier Group is the part of the M-16/AR platform (not counting the barrel, of course) that is under the most stress.

The Direct Impingement System (DIS) stresses the BCG a LOT more than a good piston operating system. All that heat and gas = stress and eventual failure.

I was in charge of second echelon maintenance on M-16s in the Army. The BCGs constantly failed inspection because the darned rifles are just not that well designed.

I personally prefer a well-designed piston operating system for the AR platform. Easier to maintain, and less stress on the critical parts.

[tulsamal]

I was once involved in a training exercise where I put 14 magazines through my M4A1 all on full auto in the course of something like 8 minutes. I did not experience any malfunctions

But that is just a sample size of one.

I was a SP4 and then a SGT back in the 25th ID on Schofield Barracks in the late 80's. Light Infantry. 1/62 ADA. For six months or so I was supported a SFC whose job it was to build and fly remote controlled aircraft in front of infantry units while they blasted away at them with M16's and M60's. All full auto. So we are talking platoons and companies all lined up at once. And mega amounts of ammo expended in short amounts of time. I was also our unit armorer. So the infantry armorer would catch problems but some overflow would also end up my way.

Things go wrong. Pins in the lower drift sideways quite often. That would happen with either type. Which is why my personal rifles have the KNS pins in them. I saw gas tubes get so hot that they would "slump" sideways in the handguards. They don't pass gas anymore when they do that. Sometimes the rifles would fail due to "general gunk" but shaking the BCG a few times and squirting it down with break free would usually get it going again. Those handguards would really be hot by the end. Some crazy privates would be pulling out their gloves so they could have fun firing some more full auto.

Of course we didn't have any piston guns to compare them with. If would be really interesting to run a range like that with 100 DI guns on one side and 100 Ruger SR556's on the other side. Honestly... which one would you rather clean if you were going to put 500 full auto rounds through it in short order?

Gregg

[dprice3844444]

DI makes for a fine target weapon but that red hot gas tube sure makes me wonder why we ever adopted DI for a service weapon
saves weight by eliminating the op rod like the m14 and garand to move the bolt

[1858]

If the standard AR15/M4 design is so reliable then why are ADCOR and others moving away from a design that requires lubrication to run well, and when lubricated has proven to be unreliable in the Middle East and similar regions where fine sand/dust is typical?

ADCOR COMPETING FOR MAJOR ARMY CONTRACT. The Baltimore Sun (5/15) reports, "Adcor Industries Inc. learned this month that it was among a handful of weapons makers selected to compete to build a possible replacement for the M4, a rifle descended from the well-known M16 and that some soldiers have criticized as unreliable in the dry, dusty conditions in Iraq." The company will compete against "some of the biggest names in global gun-making in a race to be the Army's small-arms weapon of choice in the 21st century," including Colt Defense LLC and Remington Arms Co. Adcor has invested $10 million in developing the BEAR, short for the Brown Enhanced Automatic Rifle. The BEAR made the Army's first cut but "the competition's second phase could last more than a year and will encompass rigorous testing of the weapons."

[dom1104]

People who say DI AR15s cant run without lube have never run a dry AR15 for a couple years.

If you shoot good quality full power ammo, AR15s can happily run dry for thousands of rounds.

Thats all I have to contribute.

[Welding Rod]

When I was in the Army we always ran our M16s dry... not intentionally, but not knowing that we shouldn't - and lacking any kind of proper cleaning equipment and lube. Remember cleaning a unit area with only a 1/4 cup of pine oil and one dirty wool sock for the whole outfit to share as cleaning supplies?

Still it seemed the only malfs were instigated by worn out, bad, or bent magazines.

[C-grunt]

This argument keeps popping up.

First it was that the DI system made the rifle unreliable and use the old Vietnam era M16 as an example. But then people with experience and properly built weapons showed that it is indeed a reliable system.

Now they are trying to say that the DI system will fail if you run your AR like a machinegun. But the people with experience know that a rifle isnt a machinegun. Even the venerable AK47 has problems, like catchin on fire, when used as a machinegun.

As a note. I never experienced problems with lubrication while in the middle east.

[valnar]

What's wrong with people just preferring a piston setup? I don't understand the outrage from the DI folks. History could have easily went the other way and the military standard could have been a piston design.

I never ever assume that because the military adopted something that it must be the de-facto better design. See: Beretta M9

[Bartholomew Roberts]

The Direct Impingement System (DIS) stresses the BCG a LOT more than a good piston operating system. All that heat and gas = stress and eventual failure.

What is your evidence for this conclusion? We've already shown that there is about a 40 degree difference in the bolt temperature of a Colt M4 and a Ruger SR556. Are you saying that this 40 degree difference in temperature causes Carpenter 158 steel to fail at a higher rate? Exactly how does the DI system stress the parts in the BCG - and for comparison, how does the piston stress the parts in the BCG?

If the standard AR15/M4 design is so reliable then why are ADCOR and others moving away from a design that requires lubrication to run well, and when lubricated has proven to be unreliable in the Middle East and similar regions where fine sand/dust is typical?

ADCOR is competing in the Improved Carbine Competition. Colt Defense LLC, FNH USA, Heckler & Koch, Remington Arms Company and Adcor Defense Inc. all have issued press releases saying they have been accepted to Phase II (which so far means that I can't actually think of a rifle that was eliminated by the Army). As to why ADCOR and others are moving away from that design, I would guess that intellectual property probably plays a large role. It is going to be very difficult to build a DI Improved Carbine that compete with the M4 without infringing on Colt and Knight's intellectual property. Not to mention, if your whole purpose is to replace the M4, you need to somehow differentiate your product from the product you are trying to replace. Using the same operating system that has been a major source of controversy (deserving or not) is not a smart way to do that.

What's wrong with people just preferring a piston setup? I don't understand the outrage from the DI folks.

Are we reading different threads? I missed where someone said that it was wrong for anyone to prefer a piston setup. I also didn't notice any outrage in the thread. Could you point me to examples of those?

I never ever assume that because the military adopted something that it must be the de-facto better design.

I didn't see that argument being made either. The closest I saw to it was 1858's implication that the contestants in the Improved Carbine test (all pistons) must mean that this is a superior system to DI.

Personally, I would love to see more people take the OPs approach and share the data that they used to form their opinion rather than freely sharing their opinion sans data. I may disagree with the conclusion the OP arrived at looking at the same data; but at least that is a more productive conversation than the 101st iteration of anecdotal stories about how pistons suck/rule or DI sucks/rules with people reciting things as "facts" without providing any data or useful information in support of that conclusion.

[Cosmoline]

DI has been working far better than I ever expected based on internet hype. I've had my Colt LEC for about a year now, and fired about 3,000 rounds out of it. The total failures number perhaps a dozen, and those were due to some magazine issues I've since resolved. It's actually been the second least troublesome firearm I've ever owned, second only to the CZ 452.

In contrast, the M1A piston rifle I just bought has been fun, but has had nothing but troubles and is currently back at Springfield. The piston is the source of a number of potential problems and accuracy interference. You have to remember to keep the plug screwed in tight, you have to watch the piston tolerances, and you have to clean the danged thing out with big screws. So much for making cleaning easier.

As far as lube, again it's the M1A system that requires a bunch of it. You are not supposed run that rifle dry. And the most critical lubed parts such as the roller are exposed to the elements. The AR, in contrast, runs fine with little more than a coating of CLP and some dabs of grease on a few internal points. Plus you can close up the dust cover to seal the action.

It's been said before, but the main reliability problem of the AR system has never been the DI system. It's the magazine design and interface. Adding pistons doesn't do anything to help this.

In the end, this is a carbine we're talking about. It's not a heavy machine gun or a SAW. If it's used like one, it will start to fail with or without a piston. It's to be used for periodic shooting but not for sustained continuous fire.

[jad0110]

Quote:
Originally Posted by valnar
What's wrong with people just preferring a piston setup? I don't understand the outrage from the DI folks.
Are we reading different threads? I missed where someone said that it was wrong for anyone to prefer a piston setup.

First, I have zero interest in a piston AR, but otherwise I have nothing against them.

The thing that bugs some of us are the DI myths that are just that ... myths. Myths like ARs jam because they "crap where they eat". Well, so does everything else. Until you can eliminate gun powder as the means of propellant and cycling the action, unburned residue will invariably find it's way into the action (be it a DI or piston, most of it from the case as it contracts, unseals the chamber and is dragged out during extraction).

In fact, from reading some of the stuff out there one would think the only guns that ever get fouling in the receiver/bolt are DI equipped. By that logic, handguns like Glocks and Sigs should never get dirty (barrel excepted) because there's no gas tube to collect every last bit of fouling and spray the evil stuff all over the internals. Last time I shot my SKS, I put about 100 rounds through it and there ways a nice, grimy layer of crap all over the inside of the gun. It looked like a goose defecated on the bolt :barf:. It was everywhere, ick. It shouldn't be there, according to some of the lore out there. Same could be said for the AK I used to own. Maybe they were both broken. ;) :p

So that is all we are objecting to: BS.

And as Cosmoline so rightly points out, the biggest problem with the AR/M16/M4 platform are a plethora crappy magazines floating around. They practically seem to fall out of the sky and well up out of the ground! I've only found one brand of mags that work 100% in both my ARs: Magpul PMags. Everything else I've tried has been hit or miss in both ARs, even it is only 1 mag out of 4 of brand X. I've got 3 out of spec C Products mags that won't log into place in either of my ARs when they are fully loaded; but they'll lock in when they are empty. Lot a good that does. :banghead:

In the end, this is a carbine we're talking about. It's not a heavy machine gun or a SAW. If it's used like one, it will start to fail with or without a piston. It's to be used for periodic shooting but not for sustained continuous fire.

Good point. As another poster said, after a few full auto mag dumps an AK's hand guards will burst into flames. Badge of honor or not, that probably isn't a very useful feature in combat ... at least not to the person using it :p

[crossrhodes]

Agree with Robert B. comments.
I also think until they (DOD) unass themselves with the grossly overpowered new M855A1 ammo....no battle rifle is going to last long. That ammo cut down the barrel life by 50% in LWRC's IC. Now, just think when that round heats up or gets set back. Allegedly, it's 65,000 psi in a cold chamber.