M4 and reliability: Debunking the piston myth

[WeedWacker]

Surprisingly I found this article while researching 5.45 uppers. Interesting read, surprised me by what the root cause of the failures turned out to be.

http://www.defensereview.com/the-bi...pingement-gas-system-makes-the-m4-unreliable/

Does anybody else have any supporting information on this?

 

[stubbicatt]

Thanks for sharing that article. It is nice to see someone who has facially empirical evidence to back up recommendations and opinions.

 

[demigod]

Ugghhh... The myth that pistons accomplish anything drives me nuts.

I get a kick out of guys who find a load that their piston will run on..... uhh... I thought the idea of a piston was to eliminate filth and function with all ammo variants.

 

[Rob3]

This seems like very anacdotal evidence. He even contradicts himself by saying "When the rifles become fouled, they have more drag (friction) inside the upper receiver, which slows down the bolt carrier group." So fouling is the problem? He then says his fix of replacing the buffer spring only gave him 80 more rounds. Does not sound like a fix to me. The fix is to keep the action clean by not spraying carbon all over it with every shot.

Magazines have long been known to cause jams as well. H&K did high speed camera testing to design their metal mags for Special Forces. The primary cause of jams is still fouling in the actions. Lots of armchair generals say that this is mitigated by proper cleaning and lubrication. Keeping a weapon clean is all but impossible when operating in dusty desert environments and oil will cause the dust to stick to the bolt like glue. Then comes the real question- how often do you call "Time Out" during an 18 hour firefight to clean, inspect, and PMCS weapons? I guess that one's up to the enemy.

 

[Bartholomew Roberts]

This seems like very anacdotal evidence.

Logging every malfunction experienced during training with the ASWG and 82nd Airborne and then running a controlled test is anecdotal?

He even contradicts himself by saying "When the rifles become fouled, they have more drag (friction) inside the upper receiver, which slows down the bolt carrier group." So fouling is the problem? He then says his fix of replacing the buffer spring only gave him 80 more rounds. Does not sound like a fix to me. The fix is to keep the action clean by not spraying carbon all over it with every shot.

He says fouling is not a problem with regard to M4 reliability and then demonstrates this by firing 2,440 rounds from a stock rifle that has been completely stripped of lubrication without cleaning or maintenance. You seems to be of the opinion that because fouling did eventually stop the rifle, Mr. Pannone is wrong.

From this, I get the impression you are saying that if we took a piston weapon of a similar design and stripped it of all lubrication, it would continue to run past 2,440 rounds simply because of the lack of whatever additional fouling direct gas impingement contributes? And if so, is that ability worth the tradeoffs you make to have a piston?

The primary cause of jams is still fouling in the actions.

In my experience, the primary cause of stoppages is bad magazines or bad ammunition. Fouling in the action is considerably down the list and usually the "fouling" is popped primers instead of carbon buildup.

Lots of armchair generals say that this is mitigated by proper cleaning and lubrication. Keeping a weapon clean is all but impossible when operating in dusty desert environments and oil will cause the dust to stick to the bolt like glue.

The weapon in question was totally stripped of lubrication and fired 2,440 rounds over six sessions with no problems. Are you saying it is impossible to stick to a cleaning schedule more rigorous than this?

I'd also point out that in tests by the Army and NSWC Crane, they have determined that while wet lubricant does attract more dust, it also helps debris migrate away from critical areas and that more lubricant aids functioning. I would be willing to be that in most cases the "glue" problem is caused by users not using enough lubricant.

Additionally, the author of that article is not an armchair general - he is former U. S. Marine Force Recon, U. S. Army Special Forces, and Joint Special Operations Command. He served in Iraq as recently as 2005 and was an instructor for both ASWG and the 82nd Airborne. Strangely enough, he seems to be making the same point that proper cleaning and lubrication solves (not mitigates) the problem.

Then comes the real question- how often do you call "Time Out" during an 18 hour firefight to clean, inspect, and PMCS weapons? I guess that one's up to the enemy.

I believe the author mentions using 6-8 drops of oil every 500-700 rounds on his Noveske being sufficient to keep the gun running. Is that a more onerous requirement than it sounds like? Is there some reason that isn't a viable solution?

 

[thesheepdog]

Magazines, magazines, magazines, magazines cause the most stoppages in ANY auto-loading rifle.
Don't believe me? Go watch AK's, G3's, AR's, and mall ninja piston weapons fail due to bad magazines on youtube.

Also bear in mind, the US military doesn't get PMAGs for their M4's.
Also, keep in mind that the military has a sucky way of disposing of bad magazines, and those bad magazines get re-issued.

Fouling isn't an issue until several thousand rounds-that is if the weapon hasn't been cleaned yet.

 

[Rob3]

I don't want to start an arguement, but the author only tested one high-end gun on one range. This is very anacdotal. Also, "Logging every malfunction experienced during training with the ASWG and 82nd Airborne" is misleading. Soldiers of the 82nd Airborne fire millions of rounds a year on hundreds of ranges on Ft Bragg. The author did not log every malfunction experienced by every soldier, only the ones that he saw on the ranges he was on those days. When the ASWG started up, they chose the HK 416 piston driven rifle as their main weapon, only giving them up when DA forced them to switch to the M4.

The Army's own Congressionaly mandated tests proved that the M4 tested last among all rifles tested. It was not even close to the piston driven rifles. As the Army ramps up this year for a new round of testing, the DI M4 is not even being tested. It will be compared to the winner to see if there is substantial reason to change. If the the decision is to keep the M4 it will be upgraded, likely with a piston driven upper.

I agree with you that magazines and bad ammo cause a lot of failures, but I do not agree that lubrication and proper cleaning are the answers for an M4 in adverse conditions. Maybe it worked for the author's high-end rifle in range conditions, but that does not prove that it will keep an M4 functioning in Afghanistan. My own anecdotal experience (for what it's worth) is that piston driven uppers keep the reciever much cleaner and mitigate jams caused by fouling and lack of lubrication or dirty lubrication.

 

[tirod]

Actually, you do find time in an 18 hour firefight for some maintenance. Not only that, you will NOT be firing 2400 rounds, because the soldier doesn't carry that much. He carries 8-10 30 round mags, firing 80 begs the question how he got ammo but no other strike support to solve the situation.

It's always interesting to hear the uneducated and inexperienced spout off about the conditions in battle that prevent a proven weapon from functioning.

1) MOST of the fouling in the DI action goes out the gas ports facing the ejection port in the design. It's why they are there.

2) Action fouling comes from two sources, chamber gas fouling, which is first in the action cycle, then the gas tube, AFTER it's separated from the key. This happens after the bullet leaves the muzzle, which exhausts most of it. ALL self loading weapons have chamber gas exhausting into the action. Unlike bolt guns, semi autos have dirty brass because of it.

Lubricating the bolt in use is easy, and takes seconds. Squirt the bolt through the open port, or if you have a buddy (and the service requires teams in combat precisely for just this kind of thing,) take turns shotgunning the rifle, and oil the cam pin and upper track. THAT'S the official recommended and required place for heavy lubrication per the TM. It takes less than 30 seconds.

As stated, lubricating a heavily contaminated weapon alone will make it serviceable again, enough to shoot a lot of the basic load the soldier actually carries.

In actual use, poorly maintained and defective magazines are the #1 source of stoppages in AR's. Pmags are now issue in Afghanistan to fix it. Flimsy aluminum mags with bent feed lips, bad followers, gritty rough interiors, weak springs, and dents contribute to the problem. You can't see all the defects, but you sure can buy them used from any gun show or "buddy" dumping his rejects for a bit of cash. They should be crushed, not stolen from post or purchased from a DRMO site and resold.

The point of the test was to see just how far the AR DI action will go, it seems we're still waiting for a piston owner to do the same. Funny how NONE of the piston makers have bothered - it's their selling point, right?

You don't have to like the AR design, just understand that most people don't like what they don't understand and lack experience with.

 

[tirod]

As for the infamous Dust test, the first results were biased, the Army scheduled a repeat because of it. AR haters never mention the good news.

The first test, issue rifles with issue mags, all USED, were matched against new submittal rifles with new, handpicked magazines. This in an empirical scientific testing FAIL.

If you want science, stick to it all the way. So, the second test, which the Army correctly conducted. Magazines submitted had to be fired in each and every weapon. Results? 80% less stoppages in extreme dust.

The fantasy of the DI action causing stoppages is exactly that when properly conducted empirical testing is done. It's just the fond wish of those that only want to look at it one-sidedly and can't accept facts.

PS. How much of the reputed reliabilty of POF piston uppers is actually provided by the roller bearing headed cam pin? That's one of the two friction points in the action - the other being the metal feed lips on the carrier.

Eliminate one point of friction and you get what, up to 50% less?

 

[kraigwy]

Mr. Rob;

Re-read the article. First you must understand that the author is talking somewhere north of 2400 rounds. I've been in some long winded fire fights (SE Asia) and I don't think there is a case in history where one went through that many rounds without a brake giving one time not only throw a dab of oil in the rifle but to completely field strip and clean it.

I've burnt up a M-60, but I've never had an M16 quit me. The major and most common malfunctions I've see is with loading, not the gun but the mag. A 20 round mag will cause problems if you load it with 20 rounds, a 30 round mag will cause problems if you load it with 30 rounds. Try 18 & 28 rounds respectively.

Another problem is hero's John Wayneing it, meaning taping two mags together so they can turn them around. Only to find the bottom mag full of crap. Not to mention its slower to reload with this get up.

The other problems I've dealt with is ammo, meaning reloaded ammo. Mainly people not sizing the case properly. Not using a case gage to set up the sizing die. You get all kinds of problems (many post have dealt with this). People who don't know any better are quick to blame the gun.

I've been shooting AR/M16s since 1967, every where from combat, competition to just plain old "seeing how many rounds and how fast I can get them out of the gun".

One thing I've learned is there is nothing wrong with the M16/AR system, its the idiots operating them. I've seen people jam up a single barreled break open shotgun.

As I've said many times, the Piston AR is a great solution for a non-existent problem.

I'll relate a story I've mentioned before that confirms the report posted.

Years ago I was running a sniper school for the Guard and RA at Ft. Richardson AK. I was contacted by a RA Officer requesting help disposing of some ammo. Apparently he had to show an ammo usage to keep from loosing next years allocation. I told him to bring it by.

He dropped off 30K of 5.56 and 26 K of linked 7.62. I sent one of my students to the unit to pick up 10 M16a1s and dedicated a day of training to see if we could get rid of the ammo. We did, most of it full auto. We didn't have any problems with the '16s except turning the gas tubes a bright blue, but they held up.

I don't know about heavier recoil springs, never tried them, nor had problems that would require them. Granted I haven't tried the shorter M4s, but have used the old CARs which were pretty much the same thing in the 'A1 configuration. Personally, since I shoot iron sights, I like the longer sight radius of the 20 in. barrel.

 

[theinvisibleheart]

both Colt and DOD did study on this

while back, after 2nd Gulf War, DOD commissioned an outside group to conduct small arms reliability analysis using very large sample size(thousands or tens of thousands using combat soldiers in Iraq/Aghanistan) and also, Colt did a separate study.

DOD's findings(if my memory serves me right) was that M4(both M4A1 and standard M4) did malfunction more than other arms if not regularly cleaned and if the mags were not kept clean.

Colt's findings regarding M4A1(not standard issue M4) was excessive use of suppressive fire caused excessive stress on the parts.

A simple experiment to try would be running G36, AUG, and M4 using uncovered mag in fine sand, and see which one would have lowest MRBF(Mean Rounds Before Failure).

Pretty much most modern post-1990 small arms are not gas impingement(SAR-80, G36, Tavor, etc.) for a very good reason.

FWIW, to do reliability study, you need a minimum of 30-50 samples, preferably hundreds of data points.

So the test done by the author at the link is flawed from that perspective(inadequate no. of data points).

DOD's commissioned study employed an industry standard regression analysis weighing different factors and was biased(at least the way I saw it) towards existing small arms in use. Which makes sense because for good or bad, you want your soldiers to have utmost confidence in their small arms.

 

[zombieslayer]

My experience with piston AR's is limited to the TWO s&w M&P's I bought. They were utter garbage. I'd feel better armed with a single shot blackpowder rifle than a Smith AR. They both had terrible failures both feeding and extracting. Two trips to Smith did nothing to make the ****s functional. I got rid of them and haven't looked back. So much for a "more reliable" AR. I'm allowiong some time for this bitter taste in my mouth to go away before I build my own.

 

[Rob3]

"It's always interesting to hear the uneducated and inexperienced spout off about the conditions in battle that prevent a proven weapon from functioning."

"One thing I've learned is there is nothing wrong with the M16/AR system, its the idiots operating them."

It's disappointing that an honest debate has devolved to flame throwing. I do not speak out of inexperience or lack of education. I have been in the Army for 19 years, 9 years as an infantryman (mostly in the 82nd) and the last 10 years in Special Forces. I have served two combat tours in Iraq and four in Afghanistan, all on ODAs, the last one returning in September.

I have used M16s and M4s my entire career and have relied on them in combat. The "18 hour firefight" comment I made was from personal experience. I never suggested a soldier would fire 2400 rounds at a time in combat, that was the test performed by the author of the article on a brand new, high end rifle on a range. I know the reality of riding in the back hatch of a Stryker behind three other vehicles and getting covered in dust so as to be unrecognizable. GMVs are just as bad, both inside and out. There is no way to keep a weapon spotless or keep the oil clean in a desert environment while on patrol. It is a serious problem plagueing soldiers right now.

Those who have a choice usually choose piston driven designs. Delta Force uses the HK 416. SOCOM selected the SCAR, only to take them away until Big Army makes up it's mind what it wants. The Army chose the HK XM8 years ago to replace the M4, only to be sued by Colt whose primary interest was in profits over providing the best weapons to soldiers in battle.

I don't have a dog in either fight, I just want soldiers to have the best weapon possible, no matter what it may be. I still believe the article in question is far less scientific than any of the Army's tests and biased toward a rifle the military does not use. Hopefully the new round of testing will determine a clear winner.

 

[SwampYankee]

I don't want to start an arguement, but...

Well that's good to know. And most people that start a sentence with the word "Honestly" are being just the opposite.

 

[Bartholomew Roberts]

I don't want to start an arguement

Well, Rob, I didn't think you did want to start an argument or my answer would have looked a lot more like the one Tirod gave. I assumed you wanted a discussion; but I am starting to rethink that since you apparently disregarded answering any of the questions I asked and several of the points I made.

I could understand if you just didn't get my point, that happens in discussion forums all the time; but for some reason you declined to answer any of my questions and instead just shotgunned a whole bunch of mildly relevant data concerning pistons. That makes me think you aren't interested in a discussion but just want to tell me your opinion - and while I am always interested in hearing the facts that led someone to form an opinion, I don't really care much about the opinion by itself.

but the author only tested one high-end gun on one range

The author tested a Bravo Company 14.5" that was identical to the M4 carbine issued to troops. So, no more high end than the current issue weapon - which I don't regard as all that high end. Also, I missed the part where it stated the rifle was tested on a single range. The instructor mentioned six different firing sessions; but I didn't see a discussion of where those happened. However, instead of arguing this point, I'll just concede it since I don't think it is relevant to the question of whether fouling is a problem with direct impingement and you make valid points that the actual test has a sample size of one and that clearly the author didn't log every malfunction in a division.

When the ASWG started up, they chose the HK 416 piston driven rifle as their main weapon

This doesn't tell us anything. Without knowing WHY ASWG chose this weapon, it doesn't support any argument at all. There are several reasons someone might choose a 416 depending on what specific needs they had (over-the-beach, short suppressed rifle) that don't have any relevance to fouling.

The Army's own Congressionaly mandated tests proved that the M4 tested last among all rifles tested.

The dust test tested rifles in a single environment, and let's just say that there are some documented problems with the test from several viewpoints.

It was not even close to the piston driven rifles.

We must have different definitions of "close' then. The bottom finisher (M4) had a stoppage rate of 98.6% over 60,000 rounds. The top finisher (XM8) had a stoppage rate of 99.6% over 60,000 rounds. And basically, what the test showed is that the M4 wears out faster than the other rifles, which shouldn't be a huge shock to anyone given that the M4 uses components designed for a 20" rifle system in a 14.5" carbine. By comparison, all of the other competitors were modern designs being used as they were originally designed.

But again, what does this have to do with the assertion that carbon fouling is the problem. The mere fact that the M4 finished last doesn't tell us carbon fouling is a problem. You are arguing that correlation = causation.

but I do not agree that lubrication and proper cleaning are the answers for an M4 in adverse conditions. Maybe it worked for the author's high-end rifle in range conditions, but that does not prove that it will keep an M4 functioning in Afghanistan.

As I pointed out earlier the rifle was identical to an issue M4 carbine, so not all that high end. Since the author's qualifications have already been discussed and since he was been to Iraq and worked there with the rifle type in question, I'm inclined to think he has a good idea what will keep an M4 functioning in Afghanistan.

My own anecdotal experience (for what it's worth) is that piston driven uppers keep the reciever much cleaner and mitigate jams caused by fouling and lack of lubrication or dirty lubrication.

Well, the author has described his background and testing methodology and I think we can agree it is useful in evaluating his anecdotal experience. What is yours? Why should I give it more weight than Michael Pannone's?

Edited to add:

Just saw your latest post regarding your background. I've got to say that for someone who claims such extensive experience, you aren't actually providing much substance in your responses, so I tend to doubt the claims.

Those who have a choice usually choose piston driven designs. Delta Force uses the HK 416. SOCOM selected the SCAR, only to take them away until Big Army makes up it's mind what it wants.

The SCAR hasn't been taken away. The SCAR is funded with SOCOM dollars and SOCOM decided that they had higher funding priorities than replacing the M4 they can get with Big Army dollars.

The Army chose the HK XM8 years ago to replace the M4, only to be sued by Colt whose primary interest was in profits over providing the best weapons to soldiers in battle.

That's an interesting way of looking at it. Another way of looking at it is that H&K tried to bypass the open competition concept by claiming the XM8 had already won the competition in its capacity as the lower half of the XM29 program. I consider that akin to saying "Look how we won the sci-fi grenade launcher program - here is the product minus the sci-fi grenade launcher."

When it became apparent Congress wasn't going to fund the XM8 without an open competition, the Army killed the program. The good news is that if the XM8 is all it claims to be, HK can try its hand in the M4 replacement trials and prove itself in open competition.

 

[theinvisibleheart]

would have liked to know

I routinely went well over 2500 rounds with only a few drops of oil and a bore snake run through the barrel every morning.

I would have liked to know how frequently the guy ran his bore snake.

Was it only once a day?

Also, how dirty were the mags? And how fine the sand was.

 

[kraigwy]

One thing I've learned is there is nothing wrong with the M16/AR system, its the idiots operating them

I want to apologize for that comment, it was poorly worded and I didn't mean it for anyone commenting on this topic, but "in general". I've seen some weird people in time and the comment was met for them.

But still, I should have worded that comment better.

 

[thesheepdog]

I want to apologize for that comment, it was poorly worded and I didn't mean it for anyone commenting on this topic, but "in general". I've seen some weird people in time and the comment was met for them.

I don't see anything wrong with your comment. Your comment wasn't directed to anyone here in this thread, so I doubt any offenses were taken.
There are true idiots out there operating the AR/M16 system (whether civilian, military or whomever) and that results into them hating that rifle; then the hate just floods the internet.
There is always "Operator Error" out there.

 

[Quentin2]

Very informative thread and thanks to all who have contributed. This certainly has cleared my mind and proved to me there is nothing fundamentally wrong with the direct gas impingement AR.

Let's be honest here, if you want a piston AR that's fine, go for it. But instead of trying to trash someone else's choice, admit that you have gone for a design that offers convenience (largely in cleaning) but not improved reliability. Saying it's more reliable is similar to saying the automatic transmission is more reliable than a manual transmission. It's not, it has more parts and complexity and weight and is not easier to repair - but many of us agree the AT is more convenient.

 

[theinvisibleheart]

AR reliability

my experience and understanding is contrary to that.

Even adjusted for cleaning, mean rounds between failure is higher for AR/M16 platform than other platform.

It's my understanding that other studies(DOD) found it to be the same.