The Listening / Security Halt

The following is repost from Hognose at weaponsman.com.  Weaponsman is an excellent weapon related website that is a friend to this website and also a favorite internet stop.

 

The most annoying person in the world is the write-only device. You know that guy: he never shuts up, yammering on and on, and never stopping to listen, only to take a breath. As you might expect, that habit which makes everyone want to kill him in a peacetime classroom or office, makes it easy for the enemy to literally kill him in combat.

There is much to be said about stealth and silence. The first thing that we will say is this: truly silent motion across terrain is not possible. It is an ideal for which you must strive, but even Mark Twain recognized it as nothing but a literary convention, when he was beating the defenseless James Fenimore Cooper senseless in a battle of wits:

Another stage-property that he pulled out of his box pretty frequently was the broken twig. He prized his broken twig above all the rest of his effects, and worked it the hardest. It is a restful chapter in any book of his when somebody doesn’t step on a dry twig and alarm all the reds and whites for two hundred yards around. Every time a Cooper person is in peril, and absolute silence is worth four dollars a minute, he is sure to step on a dry twig. There may be a hundred other handier things to step on, but that wouldn’t satisfy Cooper. Cooper requires him to turn out and find a dry twig; and if he can’t do it, go and borrow one. In fact, the Leatherstocking Series ought to have been called the Broken Twig Series.

It was always a Cooper white man who broke the twig, because Indians were born to patient stealth, at least in his universe. (Cooper, one must remember, was no frontiersman, but a cashiered Naval Academy midshipman). The Indian, in fact, was no more capable of silent movement than a ninja, an SF soldier, or you.

It was a crushing disappointment to learn that we would not, in SFQC, learn the Indian ninja art of silent walking on dry oak leaves. Instead, however, we learned something more practically useful: how to be quieter than the other guy, and as quiet as we needed to be.

If silent movement is not possible — and it isn’t, if your enemy can’t hear you, his dogs, with their superhuman hearing, can — then moving stealthily at night requires several things:

  1. Masking local noise with background noise;
  2. Altering the kinds of noise to attenuate sound travel; and,
  3. Periodic listening halts.

Not hard enough? Try it in MOPP.

The first two are fairly obvious: you can move much more rapidly without giving yourself away when a train is passing by, and high-pitched sounds travel poorly. (You do need to bear in mind that sound travels differently in different atmospheric conditions). The most complicated of those three principles of night movement to apply is the periodic listening halt.

Immediately after inserting, assembly, or crossing a danger area (of which more in some subsequent article), the patrol or team must conduct an initial listening security halt. While the details of the halt may vary, something like this works:

  1. Freeze in place.
  2. Remain there for five full minutes. 
  3. Maintain 360º security.
  4. Actively listen the whole time.
  5. After five minutes, make a decision: move, or continue listening?

Why five minutes? You can change that time if you like, but it’s a good minimum because it’s quite a long time to be frozen in one place. Even a patient enemy, who stops when you do, will move and give his existence and position away before five minutes is up.

Active listening? That means concentrating on listening. You’re not only listening for the enemy, but also to develop a mental picture of what normal night sounds in your location are like. What are they like immediately when you stop? If you have been halted for a time, are there animal noises that come back (and that presumably stopped while you were moving)? Knowing this gives you an edge in the woods, compared to someone who doesn’t.

After the initial halt, the element leader must have a way to silently signal the element to begin moving again. If there is sufficient illumination, hand and arm signals may be effective; if not, touch signals should be used. Only in the most extreme case should a command be verbalized, and then, it should be whispered (remember, a higher-pitched whisper will travel much more poorly than a normal-pitched vocalized word — which is a good thing in a night full of hostiles).

It goes without saying that all these modes of command and control, and the listening security halts themselves, must be practiced in controlled conditions in garrison before attempting them in the face of an armed enemy. Night combat patrol operations are at the far end of a long crawl-walk-run pipeline; they’re the Boston Marathon of crawl-walk-run.

Animal and bird sounds make both effective stealth command and control means, and also excellent “cover” if you inadvertently make a sound in the possible presence of the enemy. Do a Leatherstocking and break a twig, or snap back a branch? The risk of exposure may be mitigated, if you can fake the snort of a deer or porcine species native to the area.

Once the element is on the move, further listening security halts should be executed at relatively short but variable periods. You can set these by distance or by time; it’s also helpful to be cognizant of terrain. If you have just passed through some stuff that was impossible to be truly quiet in, like dense mountain laurel or the dry leaves of an oak forest in winter, a listening security halt on the far side should be able to reassure you about the prospect of being tracked or tailed. As in all patrol technique, principles are iron but the means of serving those principles are best mixed up so as not to simplify the enemy’s counterpatrol planning.

Don’t be the foot-shufflin’, twig-snappin’, noise-makin’ equivalent of the yammering guy in the first paragraph. On patrol, the silent man comes home; the guy who loves the sound of his own noise dies from it.

About Hognose

Former Special Forces 11B2S, later 18B, weapons man. (Also served in intelligence and operations jobs in SF).

 

 

 

Our Favorite Gun Blogs PT 1

We don’t  often speak about other blogs  here.  One reason for that is that more than a few of the bigger names have stolen some of our posts and re-posted word for word our content.  But there are a few that are outstanding in my opinion, and one in particular that is so good that is is the one website I spend almost as much time at as I do our own website here.

Weaponsman.com

To use the owners words to help set the tone for the website.

“WeaponsMan is a blog about weapons. Primarily ground combat weapons, primarily small arms and man-portable crew-served weapons. The site owner is a former Special Forces weapons man (MOS 18B, before the 18 series, 11B with Skill Qualification Indicator of S), and you can expect any guest columnists to be similarly qualified.

Our focus is on weapons: their history, effects and employment. This is not your go-to place for gun laws or gun politics; other people have that covered.”

As you can read from the “about” blurb from the wesbsite, the eponymous weapons man is indeed more than qualified to talk about small arms.   Though it is a very rare day indeed when he is only talking about small arms, or larger weapons of all types  from those used in the heavens to below sea level and in between.   That is one of the many reasons I love the website.  He touches on a variety of topics, none of them ever boring.  A personal favorite being the “when guns are outlawed then only outlaws will have ….  toilets, chainsaw, defenestration etc etc , whatever was the cause of death in the news report being spotlighted. Point being to  give none stop evidence  of what we  already know.  Banning guns will not stop murder or  accidental death.
Weaponsman  AKA Hognose, of course has multiple  technical and historical posts  on a variety of weapons,  some rare and some well known  to the gun world.
Being constantly in the thick of tech gun info myself,  some of the other posts I enjoy the most are the ones where he talks about the Special Forces world and gives  tidbits from that world only a few will ever experience.  The USSF posts often range the full history of the Green Berets, often from Vietnam to more recent times.  best of all. there is no snobbery there. No elitism. No “stay in your lane” if you want to ask a question or make a comment ( as long as it is not idiocy of one variety or another of the many varieties) in the comment section.   The comment section itself full of wonderful knowledge and experience  from the regulars.  Some of those regulars being people you may and should already know like the irreplaceable Daniel Watters from the 5.56 timeline and fellows like Ian  from Inrange TV / Forgotten weapons not to mention any amount of SF people old and new.  And of course myself.
You may even run across articles and posts speaking about our work here ,as he reads looserounds which is very flattering.
If you only want the tech stuff there is plenty of that. All posts come with multiple sources and usually links to where to buy the books or free PDFs , and other means.   A sample from the Best of Weaponsman gun tech section below  copied from the website.
  • The SAWs that never WAS: Intro, and XM106. This introduces the series, and the ugly duckling of the competition, a bizarre M16A1 variant with quick-change barrel, but still magazine-fed. Published 28 Oct 13.
  • The SAWs that never WAS: Part 2, the XM-248′s forerunner, XM235. The Rodman Labs XM235 was a radical reconception of the light machine gun which was designed to increase accuracy and reduce unintended dispersion on target. We mention in passing its abandoned XM233 and 234 competitors, all chambered for a 6.0 x 45mm cartridge. Published 31 Oct 13.
  • The SAWs that never WAS: Part 3, XM248. Rodman couldn’t go to production, so the commercial makers of the XM233 and XM234, Philco and Maremont, competed for the contract. Philco (later Ford Aerospace) won, and began to make changes to the XM235, as requested by the Army, producing the XM248. Published 2 Nov 13.
  • The SAWS that Never WAS, part 3b: the feed of the XM248. The ratchet-driven sprocket belt feed of the XM235/248 is examined using the patent documents as a basis. Published 4 Nov 13.
  • The SAWs that never WAS: Part 4, H&K XM262. Heckler & Koch’s entry was initially just a baseline for comparison of the Army’s own designs, but it performed well enough to make it into the final four (with the 106, 248, and 249). Published 9 Nov 13.
  • The SAWs that never WAS, Part 5, XM249. Like the H&K XM262, the XM249 was initially just entered to compare the FN light machine gun to the Army entries, but it ultimately beat them all. Published 23 Nov 13.

If you like our page, I strongly recommend WeaponsMan, it is highly addictive and always entertaining with a high does of humor mixed with technical discussion.

This is the first website to be mentioned in this series because it stands above all others that will come.  It has my highest recommendation and I hope you go check it out and enjoy it as much as I do.

 

 

 

Thinking About Safety

This post was originally written by Hognose, from Weaponsman.com .  He kindly gave me permission to re-post it here as a guest post and we are always thrilled to share his work. You can read more of the websites always excellent and always entertaining and informative posts by going to this link.

www.weaponsman.com

Indeed it is the best website not out own.

Larry Vickers is thinking about safety:

larry-vickers-appendix

Hat tip Miguel at Gun Free Zone, who wonders if one of the mishaps Larry’s writing about is this one. You can click the link if you like (and it’s a good tale of real-world first aid), but for most of you, the illustration will remind you what can go wrong with appendix carry.

7-June-2015-Burro-Canyon-Gunshot-Wound-Incident

That cat was danger close to living to collect the usually posthumous Darwin Award, but apparently the projectile did not connect with anything vital in his junk. Good luck, though, explaining that scar to dates. (“Go ahead and kiss it. It’s just a chancre!” probably won’t fly).

Instructor (and aidman) Stan Lee’s conclusions:

Briefing of the four firearms safety rules is of course a given, after that the first aid/gun shot wound treatment and medical evacuation plan should be thoroughly briefed as if an emergency incident had already happened to you.

He then runs through an emergency kit and emergency plan. It’s a good idea, for reasons we’ll cover in half a moment.

Someone should be able to brief all of the above in detail. That someone should be with the party from the beginning to the end. I think it’s acceptable to have the GSW kit centralized but extra credit points for wearing it.

Stan learned his first aid in the Navy. All the services teach much better and more effective first aid than they did when old dinosaurs like Tom Kratman and I went in, and even better than my old unit had on our first Afghan tour. Didn’t happen to our battalion, but in and around our time, other SF units lost guys because they exsanguinated, or developed tension pneumothorax, and the non-medics on site weren’t skilled enough to treat them. (Well, that, and medevac was weak until 2004 or so — too few frames and crews, and it’s a big country). That would never happen now; even support units get pretty decent combat life saver training.

Still, it’s a lot better to use your superior weapons handling skills so as not to have to demonstrate your superior first aid skills.

Stan makes another point (and another reason to Read The Whole Thing™ on Miguel’s site) in that simply briefing safety rules and plans at the start of a class is a Real Good Thing. In aviation, we found that when aircrews began briefing an instrument approach procedure-by-procedure, the number of errors (and mishaps) declined. In airborne operations, we found that when airborne units started doing a formal, stylized prejump briefing that everybody (especially devil-may-care skydivers) laughs at, the number of errors (and jump injuries) declined. It’s great that an American paratroop officer can command his battalion, regiment or division from a wheelbarrow pushed by one of his privates, but he’d probably rather not go down in history for that. 

IWB and particularly Appendix Carry holsters introduce risk factors that are not present in an old-fashioned outside-the-waistband holster. (We also think that schools’ focus on quick-draw engagements is usually misplaced). You can have an accident with any holster, but unless you’ve got a lot of experience, choose one that adds minimal risks.

As Larry notes, if you use a safetyless (“trigger safety”, “safe action”, anything that would have scared the horse out from under a 1909 cavalryman who had the grip safety added to the 1911) firearm you need to be extra careful about holstering and reholstering. Or, well, look at the picture.

Now, you can choose any firearm, and every one has its own risk factors. You can operate any handgun safely (we do not believe Larry has ever had an ND in God-knows how many Glock rounds), but you have to know it and its properties and operate it either with your mind on it 100%, or with skills drilled and drilled until you’re always, instinctively safe with it.

ND-shot-in-footAs the graphic we usually use with safety posts says, if you shoot yourself in a training class,  “Your [sic] Doing It Wrong.” Like this fellow in the ‘burbs of Orlando, Florida:

23-year-old man accidentally shot himself during a gun safety class at a pawn shop, according to the Orange County Sheriff’s Office.

It happened at Instant Replay Pawn Shop and Shooting Range on Colonial Drive between Dean and Rouse roads, said Lt. Paul Hopkins.

The gun went off accidentally and the bullet grazed his leg, Hopkins said.

Amazing how this guns just “went off.” No wonder newspaper guys all want to ban guns, they think of them as malevolent presences, stalking training classes and firing ranges, bent on bringing their primordial evil to bear on their hapless bearers.

Of course, that’s all bosh and nonsense. They’re simply machines, slavishly obeying the laws of physics and the input human operators apply to their user interfaces. In all history, the gun that “went off accidentally” is rarer that a comet sighting. He should admit he “set it off accidentally.”  He, too, is going to live.

He’ll probably never make that mistake again. But you know, we’re supposed to be able to learn from his mistake, rather than only learn from our own.

Thinking About Safety

More Thoughts And Follow Ups From Some Others On The M14

Last weeks post on the M14 and its variety of shortcomings certainly stirred up the ire of its faithful followers. Link to offending article below.

Indeed we had to sleep under the bed with a gun in our hand  in fear of The Old M14 Boys Club coming to take us away.  Surprising to the guns fans, many spoke up with their actual real world experience with the piece confirming the point of the article.

The M14, Not Much For Fighting ( A Case Against The M14 Legend )

Most recent is a sand test video from In Range  TV, testing the M14 against an AR15 and a MAS.  While I have been told  for years and against my own experience the M14 would laugh at a little sand, the video and reality seems to indicate different.

https://www.full30.com/video/6618755f336970e55e6c50c1fe894ff8

The boys tested the same guns earlier in the mud.  The M14 performing exactly as expected for those who know them well.

https://www.full30.com/video/9eef6b3a4eb6c8846a4c8dc4b8968bc4

My personal favorite gun blog, that is not this one, had a few words to add to the heated debate 24 hours after the festivities started with my post.    Over on weaponsman.com, a lively discussion is still on going with more than a handful of real world military users speaking up.

Loose Rounds on the M14

If you are not familiar with weaponsman.com. It is superb and is highly recommended daily reading. Description of the blogs writer and mission statement. “WeaponsMan is a blog about weapons. Primarily ground combat weapons, primarily small arms and man-portable crew-served weapons. The site owner is a former Special Forces weapons man (MOS 18B, before the 18 series, 11B with Skill Qualification Indicator of S), and you can expect any guest columnists to be similarly qualified.”

Some more discussion and viewpoint comes from a fine blog. Everydaymarksman.com. which has as a focus the owners personal quest to becoming a true rifleman and the experiences and epiphanies he has along the way.

https://everydaymarksman.wordpress.com/2015/02/02/lots-of-discussion-on-the-venerable-m14-lately/

Following some of the shrill screaming, rending of clothes and gnashing of teeth has shown many missed the point, or became so angry they did not give any consideration to the post.  Most often seen is the claim the point of the article was to talk up the AR10 or AR15, when that was obviously not the goal to anyone who can comprehend English. Nor was it an attempt to get anyone to hate the gun.  It was a discussion of its shortcomings and the honest assessment that it is far from perfect all powerful or even a decent DMR weapon, and the caliber of the gun was not even discussed. That being the other claim, that some how we were ragging on the 308, though no mention of the effectiveness was even hinted at.

While many love the rifle, nothing will change our minds from the simple truth of it. While it is  better than a tamato stake. it is far from what its blind followers would like to think.

Lastly, I am re sharing the link to some informal shooting of a custom M14 from over a year ago. While not intended to be conclusive proof of anything, it was a fun comparison of some of the classic infantry weapons of yesteryear including the M1903, M1 Garand of course the much beloved( though undeserved ) M14

More 1,000 yard shooting, M1903 , M14 And Even A Colt Commando

OLYMPUS DIGITAL CAMERA

The Big Lie About Wanat (COP Kahler), Part 2 of 2

Part 2 of the debunking of the absurd myth that the M4 has caused the death of US military people due to failures.  Once again this is the sole work of the writer from www.weaponsman.com,  THE technical website on all things military weapons related, among other topics. We again highly recommend all follow them.  Part 1 is actually below this post due to the way our website is set up.   Both are long posts but very detailed and worth reading if you are a real student of military fighting weapons.

 

In the enormous1 part one of the series, we reacted to a brain-dead article published in The Atlantic by a retired Major General, who has, since his retirement 20+ years ago, been a lobbyist for defense firms and TV talking head. (Before he got his stars he was an artillery officer). We may have more to say about our brain-dead GO in a subsequent post, but we think we raised some good points about his article. We weren’t the only ones. He also ticked off Nathaniel Fitch at The Firearm Blog, and we heard, also the guys at Loose Rounds (you know, the ones that fire M4s at 1000 yards and make the steel ring? Those guys?), and no doubt there are other places in the gunosphere flaying him. The point of today’s increment is not to make the rubble of the General’s small-arms expertise do a dead-cat-under-155-battery-closed-sheaf-fire-for-effect bounce, but to discuss the technical limits of a shoulder weapon in sustained automatic fire.

Because today is a travel day, this article was mostly-dictated for speed. Therefore, we fear we have some typos we haven’t found. Let us know in the comments.

Sustained Auto Fire and Heat

Many of the problems the M16A1 had in Vietnam, and even in adoption and acceptance prior to Vietnam, were caused by the heat of sustained autofire. It was particularly problematical after powder changes made a dramatic impact on the cyclic rate of the rifle. Indeed, Colt got a contract mod allowing weapons that had a much higher sustained rate than originally specified to be accepted.

Thermal waste is a huge problem for gun designers, and it’s been jamming automatic weapons since Maxim’s day. The heat is generated by the combustion of chemical powder in the chamber in barrel, but also by the metal-on-metal contact between bullet and barrel, which swages the impression of the rifling into the bullet and imparts a spin of hundreds-of-thousands of revolutions per minute to the bullet. The friction between bore and bullet is a significant contributor to barrel heating.

If you were in the service, you were made to memorize something about your rifle being a “shoulder-fired, magazine-fed, air-cooled, selective-fire…” weapon. The “air-cooled” seems like a historical artifact now; the last liquid-cooled small arms were the 1917 Browning machine guns, which were last used in World War II. All modern small arms of all nations are air-cooled. That means that the air around the barrel must carry the heat of the barrel away. Meanwhile, for each round, the barrel gets hotter, because firing’s ability to load up the temperature is greater than the cooling system’s ability to remove heat.  (The original M16A1 had a patented passive design for convection-driven airflow, removing the heat from the holes at the top of the handguard and drawing new air in at the bottom. Designs since then have made efforts to maintain that cooling, with little success).

Because this post is long, and involved, we’re going to split it. Ahead, we describe the bad things that happen when barrels get hot; the results of M4 cyclic rate tests (including instrumented and well-documented tests to destruction), and  Click “more” for the next three thousand or so words, a few pictures, and pointers to where you can find some of the math.

Bad Things Happen When Barrels Get Hot

The peak temperature area in the barrel is usually about three to seven inches forward of the chamber, depending on caliber (according to the references, on 5.56 mm rifles, it’s about four inches). This is where the thermal stress is at peak, and it also has to support all the rest of the barrel (and anything that may be attached to it, from a Surefire to an M9 bayonet), so when the gun is going to fail, it’s probably going to fail near here.

As more rounds are fired, more heat builds up, because it is being added at a higher rate than it can be radiated away. As the temperature rises, bad things happen:

  • You have a risk of propellant cook-off. Weapons that fire from closed-bolt are especially prone to cook-off. At a critical temperature, the powder or primer will self-initiate. As the temperature rises, the amount of time a round has to sit in the chamber to heat-soak to the point that it self-initiates declines. At first it takes minutes, then seconds, then rounds can actually cook off before the automatic firing train fires them, and finally, they can cook off out of battery. Usually other damage disables the weapon by this point. This article at DTIC shows some of the tools the .mil has to model heat transfer, and compares predicted cook-off data to observed, unfortunately in a large-caliber small arm (30mm Mk44 vehicular cannon).  They generated this equation (after Visnov) that shows :

Time to cook off (minutes) = 10.129 x 1025 x (cook-off Temp – degrees C) x 10-10.95

The cook-off temp is a constant for a given powder, and can be experimentally determined by heating the powder on a steel plate.

In the test, they did not maintain continuous fire but bursts of fire according to a firing table, then followed by letting a round sit in the chamber. Their cook-off times in live testing ranged from about 10 to about 30 minutes testing. Note that brass provides better protection from cook-off than aluminum cases, which in turn provide better protection than steel.

In another experiment, Hameed et. al. built a “Chamber simulator” and developed working chamber temperature-time curves for producing cook-offs in a 7.62mm brass case with Bullseye powder. They found that below 170ºC chamber temperature, cook-offs were unlikely, and that by about 240º, the cook-off time was down to seconds.

Cover Page

[A]n improvement to temperature sensitivity came along in 2005. [Black Hills President Jeff] Hoffman said the last change came after Black Hills technicians noticed some failures to extract (FTX) in their test M4 and short-barreled rifles, and that it was the most difficult problem to solve.

“We initially thought the FTXs were possibly related to higher port pressures,” Hoffman said. “The M4’s port pressure is around 25,000 psi, much higher than the SPR due to the location of the gas port on the respective guns. We looked at brass, powder, everything.”

It finally came down to chamber temperature. The test specification called for the ammo to be baked at 125 degrees for two hours and not exceed pressure limits when then chambered and fired. When Black Hills engineers started firing test guns far beyond the specified rate of fire, the chamber temperatures got much hotter than 125 degrees. In an extended firefight, soldiers could heat up their rifles with a few mags, and then during a lull in fighting, a chambered round would sit in a 200- or even 300-degree environment. That significantly increased chamber pressures and induced failures to extract.

“After we figured it out, I was surprised that it hadn’t come up before,” Hoffman said. “We’ve gone from bolt rifles to eight-round Garand clips to closed-bolt, select-fire rifles. SF guys never had an issue because they are trained to fire two or three rounds per target and very rarely go full auto.”

It only took Black Hills 75,000 rounds to sort out the problem—a chunk of the 250,000 rounds Hoffman figures the company fired developing and lot-testing the load. Finally, the round was issued. Interestingly, the ammo always did meet specs, even the ammo that Black Hills engineers felt needed improvement—they just found a way to make it better. The Navy began changing test specifications based on what Black Hills learned—and shared—during development and testing. The improved round was a hit, no pun intended, with operators in-theatre, and usage went through the roof. Not only did the ammo perform well for its intended purpose—long-range shooting—but did equally well in short-barreled rifles like the M4 (14.5-inch barrel) and MK 18 (10.3-inch barrel), which leads to a discussion of lethality.

  • It can cause the barrel itself to fail next time it is used. At a very high temperature, the barrel is heated until it loses its temper, which can cause an invisible (and undetectable by gaging) failure of accuracy. This was first noted with aerial machine guns in WWII, as we noted here before.
  • If continued, it can cause the barrel to fail catastrophically whilst firing. Stripped of its heat treatment and heated to the metal’s plastic temperature, the barrel droops. At first, rounds extending through it will sort of “hold it up” but soon it will be unable to contain the pressure and will burst.
  • If the barrel doesn’t fail first, heat can cause the gas tube to fail. Weakened by high temps, the tube lets go.

Any gun can cook off. The USN famously cooked off a 5″ on the destroyer USS Turner Joy in 1965 during a Vietnam War shore bombardment, killing three sailors and wounding three more.

Results of M4 Cyclic Rate Tests

Colt has, in fact, tested M4s at cyclic rate to destruction and has made these tests public. C.J. Chivers, a former Marine, has reported on these tests in a long and readable report for, of all things, the New York Times. That report was Part II of a previous report on M4 manufacturing there. We were unable to extract the Colt videos from the Times page, but it’s very much worth reading, anyway.

After the Colt tests, the Center for Naval Analyses did a report. We don’t have the report, but Kirk Ross at the US Naval Institute’s Proceedings Magazine did an excellent and thoroughly-documented synthesis of the then-known information, including the CNA report and the Colt tests, a DOD  survey of weapons users, and SOPMOD program office documents. Ross’s article is an excellent short piece on these issues and we strongly recommend it.

A lot of what we know about the M4 under duress comes from mid-1990s research. In the 1990s, as the then-new M4A1 carbine began reaching special operations units that shot them a lot, they began blowing them up. In June, 1995, 10th SF Group had two cook-offs. In September, the 1st Battalion of the 1st SFG reported multiple problems, including cook-offs. In May, 1996, 7th Group blew one up in its then-home-station of Fort Bragg. In August, 1996, 3rd Group blew one up on an African JCET; one USSF was injured by gun shrapnel. 5th Group and the 1st Ranger Bat also blew up guns around this time, and that began to worry SOF soldiers and leaders — and the armament procurement guys. The Army resolved to test M4s to destruction to determine what was going on. The one thing they knew was that the destroyed guns had been fired a lot, primarily full-auto fire at cyclic rates, often “burning up” excess ammunition at the end of an exercise (wasteful, but the Army makes it very difficult to turn back in unused ammo, and the Air Force is snippy about transporting it).

In 1996, ARDEC’s Jeff Windham conducted tests-to-destruction to determine whether, as then rumored, M4 barrels were more prone to failure than the M16A2 barrel. These were early M4A1s with the M4 profile barrel (like the one we carried in Afghanistan), and the M16A2 controls in the test were modified to fire full-auto by subbing in M16A1 fire control parts. The guns were fixtured and fired full-auto. The intent was to fire one of each fully-instrumented weapon to failure. Initially, an M16A2 was destroyed:

The M16A2 was fired continuously using 30 rounds bursts. Shown in Table I are the rounds to failure, time to failure and maximum barrel temperature of the barrel. Muzzle flash increased and there was a distinct change in the sound of the weapons firing approximately 30 rounds before the barrel ruptured. There was also noticeable drooping (about 1 inch at the muzzle) of the barrel just prior to the barrel rupture. The barrel ruptured at 491 rounds with an approximately ½ inch hole in the top of the barrel about 8 inches in front of the chamber. The barrel was bent approximately 5 degrees and bulged in several locations along its length (see figures 4, 5, and 6). A plot of barrel temperature versus time at each thermocouple location is shown in figure 7.

Given the hypothesis that the M4 would die before the A2, Jeff fixtured the sacrificial M4A1 and set up 18 magazines, containing 540 rounds, and then fired them. But while the barrel was ruined, it didn’t actually burst:

The M4A1 Carbine was fired for 540 rounds. It was thought the M4A1 barrel would rupture well before this point, therefore only 540 rounds were loaded for firing. This weapon’s barrel was noticeably bent and bulged at the end of the test (see figure 8). A plot of barrel temperature versus time at each thermocouple location is shown in figure 9.

m4a1_fired_to_destruction

Oops. Back to the testing bench, with another M4A1 selected as a sacrifice to the gods of knowledge.

A second M4A1 Carbine was fixtured for testing and fired until barrel rupture. Muzzle flash increased and there was a distinct change in the sound of the weapons firing approximately 30 rounds before the barrel ruptured. There was also noticeable drooping (about 3/4 inch at the muzzle) of the barrel just prior to the barrel rupture. The barrel was ruptured at the 12 o’clock position approximately 4 inches in front of the chamber. The rupture was approximately 1V4 inches long and 5/8 inches wide. The barrel around the rupture was bulged out about 30 percent larger than its normal diameter. The barrel was bent at the hole approximately 3 degrees (see figures 10 and 11). A plot of barrel temperature versus time at each thermocouple location is shown in figure 12. There was an approximately 30-second delay in firing of this sequence which can be seen in the temperature plots. This delay allowed additional cooling of the weapon and may have increased the number of rounds to rupture by 30 to 60 rounds.

Here is the Table 1 from the report. The other figures and tables referenced in the quotes are in the report, which is linked in the Sources below, although the photo reproduction is of very low quality.

fire_to_destruction_table_1

SOCOM sent a safety message as far back as 1996, presumably based on Windham’s research (although we didn’t notice if they said that) about cook-offs with sustained fire. It is reproduced in this archived ARFCOM thread. We recall receiving this message with a red-bordered safety cover sheet. The thread poster has good advice. Here are a couple of lines from that message:

Sustained firing of the M16 series rifles or M4 series carbines will rapidly raise the temperature of the barrel to a critical point.

Firing 140 rounds, rapidly and continuously, will raise the temperature of the barrel to the cook-off point. At this temperature, any live round remaining in the chamber for any reason may cook-off (detonate) in as short a period as 10 seconds.

Sustained rate of fire for the M16 series rifles and M4 series carbines is 12-15 rounds per minute. This is the actual rate of fire that a weapon can continue to be fired for an indefinite length of time without serious overheating.

The sustained rate of fire should never be exceeded except under circumstances of extreme urgency. (Note: a hot weapon takes approximately 30 minutes to cool to ambient temperature conditions).

Cook-offs out of battery result from a round which cooks off when the bolt is not locked or a round which cooks off as the user is trying to clear the weapon.

Burst barrels result when the weapons are fired under very extreme firing schedules and the barrel temperature exceeds 1360 degrees Fahrenheit. When the barrel reaches these extreme temperatures, the barrel steel weakens to the point that the high pressure gases burst through the side of the barrel approximately 4 inches in front of the chamber. This condition can result in serious injury.

That is, of course, exactly the failure mode in the first M4 video at Chivers’s report. And this is from a message from 1996, so SOCOM’s weapons experts knew it almost 20 years ago, and more than 10 years before Wanat.

600-700 degrees F is where cook-offs begin, and that’s reached in as few as 140 rounds on rapid semi-auto fire.

Here’s a table with some key temperatures for you:

Temp F Temp C Rounds Comment
230 110 30 semi-auto M855 in M4
278 137 30 full-auto M855 in M4
600 316 140 semi-auto; threshold of cook-off
700 371 ? frequent cookoffs, barrel weakened
1360 737 ~500 semi or full, catastrophic failure
© Weaponsman,com 2015

How to Deal With Heat Limits

The Training Answer: First, every GI should see those Colt test videos and know what his gun can, and can’t, do. While the Black Hills guys were correct in noting that SF/SOF guys usually manually fire single shots or short bursts, even most of them don’t know what happens when a gun goes cyclic for minutes at a time. A good video explaining “why you can’t do that” would be a strong addition to training, not only for combat forces, but for support elements who may find themselves in combat and feel the urge to dump mags at cyclic rate.

The Morale Answer: Every GI should see the same done to AKs as well. There is a myth perpetuated by pig-ignorant people (like General Scales) that the AK series possesses magical properties and that the American weapons are crap. In fact, nobody I know of at the sharp end is at all eager to change, perhaps because the laws of physics and the properties of materials apply just as firmly to a gun originally created by a Communist in Izhevsk as they do to a concept crafted by capitalists in California. If you’ve ever fired an AK to destruction, you know that it grows too hot to hold, then the wooden furniture goes on fire, then, if you persist on firing it full-auto, it also goes kablooey. Not because there’s anything wrong with this rifle, but the laws and equations work the same for engineers worldwide.

The Systems Answer:  As you can see from the Colt videos, if you clicked on over to Chivers’s article, thickening the barrel nearly doubled the rounds to catastrophic failure on cyclic. An open/closed bolt cycle might have practical benefits. They wouldn’t show up in sustained heavy firing like the destruction tests, but they might show up in how a weapon recoups from high temps, and open-bolt autofire would eliminate cook-offs, at least. But any such approach needs thorough testing.

The Wrong Answer: Replacing the M4 with something like the SCAR or the HK416, something that is, at best, barely better, that is much more maintenance intensive, and that, contra Scales’s assertion that his undisclosed client’s weapon is “the same price,” is twice (SCAR) or three times (416) the money. (The 416 mags are the best part of the system, though).

It would be interesting to duplicate Jeff Windham’s M4A1 destruction tests with AKs and with other competitors, like the 416. Scales says a piston system like those (never mind that each one is a very different design) would not fail under the conditions seen at Wanat. We’ve seen from the information here, that the failure of firearms under high rates of fire is driven by the physical problems of waste heat and metallurgy. Our prediction is the laws of physics apply in Russia and Germany as well.

Did Weapons Cause Deaths at Wanat?

We’ve talked about how the weapons fail, when they fail, today. But in the previous post, we were looking at this in the context of a very important question: did weapons deficiencies cause deaths at Wanat? We reached our conclusions. In The Atlantic, Major General Scales, the undocumented lobbyist and long-retired talking head, reached the opposite conclusion, and asserted that the nine fatalities that day resulted from, specifically, M4 failures. We are not sure whether his problem is lack of familiarity with the material we’ve presented here, or whether it’s an integrity issue, but we think we’ve rather conclusively made the point that any honest answer comes back, “No.”

But it’s worth noting what the other investigations decided.

  • The historical investigation, both the Cubbison and the final, come up, “no.”
  • The RAND report does not fault the weapons. It does suggest some theoretical future weapons developments, such as miniguns or thermobaric weapons, and points out the dead-space problem without making a specific suggestion of how to address it.
  • The Army 15-6 investigation, came up “no,” and said so explicitly.
  • The DOD Inspector General investigation, that was extremely critical of the leadership of the company, battalion and brigade, did not mention weapons as a factor.

And so we’re not really in bad company, even though were on the other side of a Major General on this.

Notes

1. A good web article is about 300 words. A good newspaper column is about 700 words. Because we have faith in our readers’ ability to follow pieces of greater length and complexity, we frequently go to 1000 or even 2000 words (although our mean comes in around 600). That article was 3,129 words. And well illustrated, too.

Sources

Chivers, CJ. The Making of the Military’s Standard Arms, Part II. New York Times (online): 12 Jan 2010. Retrieved from: http://atwar.blogs.nytimes.com/2010/01/12/m4-and-m4a1-guns/?_r=1

Department of Defense. MIL-STD-3029: Department of Defense Test Method Standard: Hot Gun Cook-Off Hazards Assessment, Test and Analysis. Washington, DC: DOD, 23 July 2009. Retrieved from: http://everyspec.com/MIL-STD/MIL-STD-3000-9999/download.php?spec=MIL-STD-3029.022917.PDF

Guthrie, J. Reviewing Black Hills’ MK 262 Mod 1 Ammo. Shooting Times: 21 Mar 2012. Retrieved from: http://www.shootingtimes.com/ammo/special-forces-to-civilians-black-hills-mk-262-mod-1-review/

Hameed, Amer,  Azavedo, Mathew, and Pitcher, Philip.  Experimental investigation of a cook-off temperature in a hot barrel. Defence Technology.Volume 10, Issue 2, June 2014 (28th International Symposium on Ballistics), Pages 86–91. Retrieved from: http://www.sciencedirect.com/science/article/pii/S2214914714000385

Ross, Kirk. What Really Happened at Wanat. Proceedings Magazine, July 2010. Vol. 136/7/1.289. Retrieved from: http://www.usni.org/magazines/proceedings/2010-07/what-really-happened-wanat

Smith, Herschel. The Captain’s Journal. Multiple posts on Wanat linked to his Battle-of-Wanat category. Basically, Hersh has beaten all this ground years before (and we’ve even cited his reports here, before). Retrieved from: http://www.captainsjournal.com/category/battle-of-wanat/

Windham, Jeff. Fire To Destruction Test of 5.56mm M4A1 Carbine and M16A2 Rifle Barrels. Rock Island, IL: Engineering Support Directorate, Armament Research, Development And Engineering Center. September, 1996. Retrieved from: http://www.dtic.mil/cgi-bin/GetTRDoc?Location=U2&doc=GetTRDoc.pdf&AD=ADA317929  (Abstract: http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA317929).

Witherell, Mark, & Pflegl, George. Prediction of Propellant and Explosive Cook-off for the 30-mm HEI-T And Raufoss MPLD-T Round Chambered in a Hot Mk44 Barrel (Advanced Amphibious Assault Vehicle – AAAV). Watervliet, NY: Army Research Laboratory/Benet Labs, March 2001. Retrieved from: http://www.dtic.mil/dtic/tr/fulltext/u2/a388280.pdf