Category Archives: Machine Guns

Before there was “Reverse,” it was just “Engineering.”

So, let’s take a look back at something we’ve been discussing recently: reverse engineering. The term is a relatively new one, but the practice is older than engineering itself. When you get right down to it it’s just “copying.” And manufacturers have been doing that since… Well, since sometime very soon after they first started manufacturing!

Sometimes the drawings (here a Swedish BAR from come after the engineering.

Sometimes the drawings (here a Swedish BAR from come after the engineering.

Bear in mind that parts were not made from drawings until well into the 20th century. Specific jigs and measuring tools were made to ensure that parts were produced in conformance with a physical, mechanical prototype. And designers didn’t work from, or produce, drawings, at least not exclusively: a designer like John M. Browning produced a physical, working model, and brought that to his manufacturing partners. They engineered it for production. Sure, he made drawings, or had them made, but that was for patent purposes (below, right).

bar_patent_hqIn the early twentieth century, talent in gun design usually resided in a different man than talent in production engineering. (There were some who could do both, like John Garand and some of the Russian masters, like Vladimir Grigoryevich Fyodorov, but they were rare).

So in John Browning’s day, putting any of his guns into production was, to one extent or another, an exercise in what we would today call reverse engineering. Production engineers would review the prototype, gain an understanding of its design philosophy and features from the designer, and then figure out how to mass-produce the weapons. And the World War I Browning Automatic Rifle may be the greatest reverse engineering saga you haven’t heard.

Winchester, the firm, was struggling when it was tasked to produce Browning’s new designs, the Browning Automatic Rifle and the yet-nameless .50 caliber machine gun, with priority to the auto rifle. There was only one problem: there was only one prototype or specimen BAR in the world, and Colt had it, and was re-engineering it all day long, Monday to Friday. In the spirit of wartime cooperation, Colt would let its New Haven rivals borrow the new firearm – for a weekend.

Winchester 1918 BAR

Winchester, which had seen massive orders, but incurred staggering debt in order to fulfill them, needed the order badly. They accepted what seemed to be an unreasonable offer.

In September 1917, Winchester was instructed to commence tooling up for the manufacture of the Browning Automatic Rifle (BAR). Edwin Pugsley, then Manufacturing engineer, went to the coat factory to see the only existing model. Since the BAR was needed at Colt during the work week, it was borrowed for a weekend, and in that time drawings were made and the project begun. By the end of December The first Winchester BAR had been completed. Production was well on by March, and by Armistice Day, November 11, 1918, Winchester had made approximately 47,000.

Winchester also had begun construction of the Browning .50-caliber machine gun and had a working model completed within about two months. That gun, however, never entered into production, because of the end of hostilities.1

The earnings from wartime contracts, including 1917 Enfield rifles, riot guns, and the BAR, were substantial: $76 million. It wasn’t enough to retire all of Winchester’s debt, a substantial $16 million, but they were able to pay off about half of it. The company still had to reorganize and the Winchester-Bennett family wound up giving up control.

Winchester 1918 for sale by Craig Gottlieb. It has some M1918A2 parts (stocks & trigger guard with mag "ears").

Winchester 1918, once for sale (no longer) by Craig Gottlieb. It has some M1918A2 parts (stocks, flash hider, & trigger guard with mag “ears”). More images of the same gun at the link (all the M1918 photos in this post are of that firearm).

But it’s hard to beat, in the annals of reverse engineering, the one-weekend crash metrology and documentation Winchester had with the world’s only BAR before delivering it back to the Colt engineers in Hartford, and that produced the wartime BARs and led to the rifle’s future as the basis of fire in the American rifle squad, not in time for that war but in plenty of time for the next two. This is especially remarkable when you consider the sheer complexity of the BAR. It has scores and scores of parts.2 (Winchester cheated a little, for example, by using the sight they were already producing for the M1917 Enfield rifle).


The problem, of course, with two independent reverse-engineering projects? Parts from the Colt Monitor don’t interchange 100% with Winchester’s military BARs. But what do you want for two days?

Update 1000R 8 Apr 15

This post has been corrected. Several (more like twenty) unproofread dictation failures have been fixed. We’re not sure we got them all. Thanks to Ullr in the comments.

“I don’t need to check it… it was done last night, just needed the pictures.” Zug.


  1. Wilson, RL. Winchester: An American Legend. New York, 2004: Chartwell Books. p. 171.
  2. As well Hognose knows. He was sure he was going to flunk BAR in SF Light Weapons School in 1983. “Cups and cones, cups and cones….” He pulled out a pass on the BAR, but got a downcheck on the M3A1 Grease Gun, of all things (IIRC you could get two downchecks, or maybe it was three. Didn’t want to test the limits).



Transferable History

We’ve featured an MP.18-II before, which is a later iteration of this exact same gun, with a magazine well reconfigured for straight magazines. (It led in turn to the MP.28, the Lanchester, and the Sten, by fairly direct process of derivation). But this gun, the MP.18-I, is the granddaddy of them all, and it could be yours.

MP.18-I 03It is certainly the first widely produced submachine gun, defined as a shoulder-fired infantry weapon firing a pistol cartridge with an automatic or select-fire mechanism. A blowback mechanism, it showed the way for many designs that would follow through three generations of submachine guns, until the rise of compact versions of intermediate-cartridge assault weapons would replace most of them.

Some would say it has a face only a mother could love:

MP.18-I 28


And it’s just as awkward looking from behind. MP.18-I 24

The drum magazine is so odd looking because it was already in production for the Lange P.08, the “Artillery” Luger. Rather than try to design a thirtyish-round magazine, the engineers at Theodor Bergmann in the weapons-manufacturing center Suhl, Germany, did what many later gun designers would do and borrowed a proven one.

MP.18-I Snail Drum 03


The gadget with the lever is the magazine loader, a must-have for these unique mags. Note the sleeve that fits on them for SMG use.

MP.18-I 06

Like all first-generation submachine guns the MP.18-I is made using the rifle processes of the early 20th Century. It is primarily made of steel parts machined from billet or forgings, richly blued; and the stock is solid walnut. If four years of relentless naval blockade had damaged the German Empire’s war production capabilities, this gun doesn’t show it.

The auction has a very reasonable opening bid, for what it is, but there is also a reserve. No, we don’t know what the reserve is.

As the catchy song goes, what does the ad say?

This is a really nice example of the early 9 mm German submachine gun used in WWI. MP18-1 was the first true Submachine Gun. This is not all matching, but is an excellent example with an excellent bore.

These are very rare and hard to find because most MP18’s were modified to accept the straight magazine instead of the drum magazine.

There was a show on the tube, the one with that perv guy, where they bubba’d up a later MP. 18-II to resemble this, so you might want to ensure that this is not the Bubba gun version.

It has a 1920 stamp on the receiver so it was used by the Weimar Police.

This comes with 2 drums with adapters and 1 drum loading tool. These drums are the same drums used with the Artillery Luger. This is C&R fully transferable and is currently on a form 3.

via German WWI MP18,I with 2 Drums & Loader : Machine Guns at

If you’re familiar with later German SMGs, the bolt and striker of the MP.18 look pretty familiar:

MP.18-I 25

The simplicity of this firearm was so elegantly perfect for its purpose that it spawned hundreds of work-alikes, few of which improved on its basic function (after replacing the overly complex magazine).

This may look like a lot of pictures, but there are way more at the auction link — something like 30 of them all told. You know you want to click over there anyway.

Sure, it’s more than our pickup cost, new, and it’s almost 100 years old. But on the other hand, our pickup will be worth approximately $0 in ten years, and an original MP.18-I is unlikely to lose much value. (If you buy it into a business you can even try depreciating it and see if the tax guys let you).

In case two drums aren’t enough for you, the same seller has a third, too. Without loader, but with dust cover. They’re all First Model snail drums. Annoy a totalitarian, buy a 32-round magazine.

third drum

One nice thing about this seller’s auctions is that they run for a good, long time. The MP.18 has eight days to go. (Serious bidders may not show up until close to the end. Don’t read too much into lack of bids on an auction when it still has weeks to run).

Another nice thing about these auctions? They give all of us the chance to see many rare collector pieces. We can’t own them all, but we can get eyes on them when they change hands. How cool is that?

How Did the FG-42 Selector Work?

We were asked that yesterday and we pontifically pronounced, “it fired from the open bolt in automatic mode, and from the close bolt in semi.”

This one's an SMG Guns semi clone. Pretty, though, innit?

This one’s an SMG Guns semi clone. Pretty, though, innit? Images do embiggen with a click.

Then we rested back on our laurels as Gun Expert and —

“Well, how did they make it do that?”

“*!” Hmm… How did they? “Let me get back to you on that.”

Fortunately, several references on the shelves explain it in terms our walnut sized brain could grasp. It turns out it was very simple, when you consider how complex some of the other design options made the FG. And it imposed some trade-offs, costing the rifle significant semi-auto accuracy as the price of that mechanical simplicity. Let’s walk you through it.

It worked exactly the same on the First and Second model of the FG, by the way; so we will use images of both in this post.

FG42-0034- grip FW

This image is from a crudely DEWATted Second Model FG that was examined by Forgotten Weapons. There’s a great set of images there, and the gun’s internals are mostly present and correct.

The selector switch is on the left side of what we’d call the grip frame. (The German manuals call this part the Lager which can mean holder or receiver, too, but we’ll stick with “grip frame”). The selector swings through 180º of travel; knob forward covers an “E” for Einzelfeuer (“single fire,” semi-auto), and knob rear clicks on to “D” for Dauerfeuer, (“continuous fire,” automatic). Note that the letter that shows is the antonym of the function you get. Don’t ask us; Hermann Göring was not available to take complaints.

FG-42 exploded view

Comparing the Bedienungsanleitung (manual) image of a First Model to the photo of the second model above that, we can see how the trigger works. The trigger pivots on a pin forward of, and slightly below, the selector switch. The axis of the selector switch is also the axle of the sear (in the diagram, Part B8 Abzughebel, literally “trigger lever”). The sear nose (Fangnase, “catch nose,” B8a) is the hardened end of the sear that engages a notch (if you learned engineering English in Britain, a “bent”) in the operating rod (Verschlußführungsstück, “bolt guiding piece,” Part D10).

There are, however, two notches in the op-rod. One is towards the front end, and mostly right of center. One is towards the tail end, and mostly left of center. You can make out the two notches in this Forgotten Weapons photo.

FG42-0003_FWRotating the selector moves the sear laterally either right to align with the front-end notch, or left to align with the tail-end notch. If it aligns with the tail-end notch, a disconnector (Unterbrecher, literally “interrupter”, B9), works by disengaging the trigger from the sear until the trigger is released (i.e., normal semi-auto trigger reset). Thus the selector engages the sear nose with either the nose-end notch, which holds the op rod and bolt assembly to the rear, or the tail-end notch, which holds the op rod and firing pin only to the rear, allowing the bolt to lock fully into battery.

Releasing the trigger releases the op-rod, then. If the weapon is on full automatic, the bolt and op-rod come forward, the bolt locks, the op-rod finishes its full travel, and the firing pin initiates the cartridge. The whole thing cycles again and continues to do so until the operator releases the trigger. When he does, the bolt is held in automatic battery — to the rear.

These schematics are from Allson & Toomey's Small Arms, pp. 226-227.

These schematics are from Allsop & Toomey’s Small Arms, pp. 226-227. The depiction of the selector in these drawings is how we came to understand that the selector (“change lever” in British English) covers the appropriate letter for type of fire selected.

If the weapon is on semi (selector knob swung 180º to the front), the trigger releases the op-rod, which brings the firing pin down on the primer. The bolt then cycles, but returns to semi-auto battery, closed bolt on a live cartridge, regardless of trigger position. The disconnector rides in the notch forward of the rear notch (here “bent”) only to disconnect when in Semi.


If you’re feeling envious of FG-42s, you can buy an excellent semi repro from SMG Guns, you can pay more than a new luxury car for a transferable, or you can take the following image, a pile of steel, wood and aluminum, and a set of files and try to do what SMG did:

FG-42 Type II exploded view

It may take a while. Best of luck to you!

Now, the FG42 wasn’t the last word in open/closed bolt hybrid firing mechanisms. As mentioned, having the whole op rod and firing pin move was inimical to accuracy. This not only increased the motion of the firearm on firing, but it increased lock time substantially, giving that motion more time to work on sending your projectiles wild. But that was a tradeoff that designers at Rheinmettal accepted for their simple and reliable open/closed bolt mechanism.

As we’ve seen, waste heat is a real killer of combat weapons in automatic fire, and by extension, a potential killer of the men who fire them. Firing from an open bolt reduces the incremental temperature increase per automatic round fired, by allowing more air to circulate and more of the potential radiative area to be exposed to ambient-temperature cooling air. This has the side effect of moving the critical temperature area or point further up the barrel from its usual position 5 to 8 inches in front of the chamber.

Firing from an open bolt also prevents cook-offs. Contrary to common misconception, cook-offs are usually not instantaneous but result from a round remaining chambered in a hot barrel for some seconds or minutes. For a cook-off to be instantaneous (and risk an out-of-battery ignition) the temperature has to be extremely elevated. For a routine cook-off, which can take some time to happen, the biggest danger is that no one is expecting the weapon to fire, and people may be in an unsafe position forward of its muzzle at that point.

The FG42 was a remarkably good weapon, like many WWII German weapons. Not good enough for them to win the war, fortunately; it was the very devil to produce (ask Steve at SMG!) and was produced in the sort of numbers that would be a rounding error, or the scrappage involved in training some new line workers, in American, British or Russian production. The US produced, for example, about 40 times as many BARs as Germany produced FG42s; Russian production of the pan-fed DP28 LMG was easily double that. (German production wasn’t as dismal as you might think. They produced more rifles and carbines of all types than the USA did. But they did have a tendency to engineer something very good, and then fail to build it in numbers that would make a difference).

“The Gun is its Own Tool Kit.” — Browning ANM2

This is Your Gun pG1One sign of a gun design that is not completely thought through is a requirement for special tools for disassembly. These days, most guns are designed for disassembly without any kind of offboard tools. But this was not always the case. John M. Browning was one of the first designers to consistently design guns to be disassembled without anything special. And it was a bit of a marvel, as the tone of this excerpt from a naval aerial gunner’s manual called This is Your Gun reveals:


In an emergency, the gun can be stripped with nothing but its own parts as tools. Use the point of a cartridge or the cocking lever pin to depress the oil buffer body spring lock.

Key parts in the oil buffer assembly:

Key parts in the oil buffer assembly: Oil Buffer Body Spring Lock (14a); Accelerator Pin (13), Accelerator (12). Oil Buffer Tube Lock (11)

Use the cocking lever pin to drift out the sear stop pin and accelerator pin.

Many of the parts mentioned are in the Bolt Group. In the order that they're mentioned:

Many of the parts mentioned are in the Bolt Group. In the order that they’re mentioned:  The Cocking Lever Pin is Nº 7. The Sear Stop with the Sear Stop Pin is Nº 8. The Cocking Lever is Nº 6.


 Use the flat tip of the cocking lever as you would use a screw driver to remove and replace the sear stop, oil buffer tube lock, the cover latch spring, and cover extractor spring. Use the oil buffer tube lock to pry the handle of the trigger bar pin out of its hole in the side of the receiver.

Use the sear stop pin to drift out the belt feed pawl pin.

The Belt Feed Pawl Pin is #5 in this illustration. US Navy.

The Belt Feed Pawl Pin is #5 in this illustration. Cover Latch Spring is #8, Cover Extractor Spring #9. US Navy.

But use these methods only when absolutely necessary and take care not to damage the parts used as tools. Never use the driving spring rod assembly as a tool.

Conversely, having a gun like this that can be disassembled and reassembled in field conditions without a bench full of tools is a marker of good design. This kind of design is more commonly encountered now than it was in Browning’s day, which speaks for Browning’s lasting positive impact on firearms design.

507th Follow Up

We have a few small details to add to this morning’s 507th post.

Some bright spark at the El Paso Times requested, after hearing how the unit managed to have M16A2s, M249s and an M2 all go tango uniform in combat, something that seemed reasonable to the reporter: all the records about the weapons. We didn’t find the original article online, but believe that this repost here is authentic.

…all records and documents about the weapons that jammed during the March 23 ambush that led to the death of nine Fort Bliss soldiers were destroyed in the Iraqi attack and that there is no way to trace the weapons’ histories.

The Army, responding to an El Paso Times request under the Freedom of Information Act, said any official information about the weapons used by Fort Bliss’ 507th Maintenance Company was lost on a supply truck taken into combat.

The disclosure that the records were lost shocked, bewildered and further angered relatives of soldiers who were killed in the early morning ambush, which is among the worst losses for the U.S. military during Operation Iraqi Freedom. In addition to the nine Fort Bliss soldiers killed, two from the 3rd Forward Support Battalion were killed, five soldiers were wounded, and seven soldiers were taken prisoner.

“Capt. Troy King (507th commander) stated that he does not have any historical data on weapons involved in the enemy contact,” June Bates, Fort Bliss freedom of information officer, said in a written response. “He lost his motorpool truck and all documentation.”

Bates said King’s records, which were kept in the motor pool, were stored in his supply truck, which was also “involved in the enemy contact.”

This is a little bit disingenuous, because even in 2003 the 507th, like any unit, would have had a property book maintained on computer at a higher level. For example, the 507th’s superior unit would have had a computer run of all the unit’s property, which would have to be reconciled at intervals (annually, or at a change of command, or on deployment/redeployment) with the property actually on hand. Most everyone who’s served a hitch in the Army has endured a property inventory. In 2003, it would have required unit commanders and logistics officers/NCOs to work off a green-and-white-banded, impact-printed inventory. This document records every single piece of organizational property by NSN, quantity, and, in the case of sensitive and serial-numbered items like weapons and optics, serial number.

So all of the 507th’s paperwork could go up in smoke, but two pieces of information clearly at hand were the serial number inventory of the unit’s weapons as-supplied-by-higher, plus, the serial number inventory of the surviving weapons. The only thing you can’t do without the company level records is determine what individual was assigned which weapon. You might be missing nine M16A2 rifles, and know their serial numbers, but you can’t say that this one was the one used by SGT Walters and this other one was 1SG Dowdy’s. Those assignments are lost (although there’s a long-shot possibility some of the soldiers who lost their weapons but survived, the wounded and captured troopers, might actually know their rifle’s serial number. About 1 in 20 soldiers seems to memorize this).

The paper doesn’t seem to know what they were asking for, or where to get it from, or how to ask for it. Soldier-hating journalists that they were, they were looking for some “gotcha” that they didn’t get.

The El Paso Times had requested the history of 31 weapons the soldiers carried during the ambush. The request sought information about weapon repairs, the weapons’ ages, and the manufacturer and condition of each weapon assigned to the 507th soldiers involved in the attack.

The Army does not maintain longitudinal records on individual weapons at all, which may be a mistake. This is one of the reasons for the shot-counter initiatives we’ve seen in these pages several times. We’ve also seen that, while the Army insists they’re fully equivalent, an arsenal-rebuilt weapon is statistically less reliable than a new one. Those two claims are actually both true, as impossible and contradictory as that sounds. The reason is, the Army has a criterion-referenced standard for weapons that both new and rebuilt weapons must meet. But, unlike the Army’s own depots, where a reject just goes back through until it passes, it’s a big deal when a new weapon coming in from an industrial manufacturer like Colt, FNH or General Dynamics-Saco doesn’t meet standard, and it leads to some pain and suffering for the manufacturer. As a result, they inspect parts, processes and weapons to a higher standard to ensure that the low tail of the bell curve still clears the Army’s criterion.

Because personnel files were lost in the ambush and no duplicates exist, the 507th is now trying to re-create the information. Also, [Ft Bliss Spokesman Jean] Offutt said, some of the weapons the 507th used haven’t been recovered.

“But shortly before the soldiers deployed, all of the weapons were certified and serviceable,” Offutt said. “The weapons were fired on the firing range before they deployed.”

Again, all that means is that the weapons were Technically Inspected (TI’d) prior to the deployment and met in-service standards for that particular weapon. As we’ve also often stated, in-service standards are considerably lower than initial-acceptance standards, because they make allowance for wear and tear, and all the slings and arrows of field use by the American GI, which can include using a pistol for a hammer, and a rifle barrel for a pry bar. The example we use in explaining the standard is the M16A1 technical standard for group size: a new gun must meet a fairly loose specification of 4 MOA, but a gun is not taken out of service for dispersion until its groups are over 7 MOA.

Please read the comments on the earlier post. Kirk has a particularly good one, but it’s not the only good one by any means.

It’s all fine and good to practice maneuver warfare and tell yourself you’re punching through the enemy’s resistance and bypassing his pocketed troops. but if you’re going to do that, having the Tail-End Charlie of your corps movement be a combat service support unit that is completely lacking in the experience and mindset of combat arms units is not a good idea.

The soldiers of the 507th did well when you consider that they were a unit expected to be, “in the rear, with the gear,” but found themselves fighting against enemy regulars, regulars, and even tanks.

Their sacrifice was not in vain, because the Army has considerably increased weapons and combat training for support and service support soldiers since then. Today’s maintenance, supply and technical soldiers may suddenly be thrown into a fight like this, but if so, they’ll have some training to fall back on; They won’t be as far over their heads as the 507th was that day in 2003.

PPShooting Around Corners

Waffen Revue 25 - StG44If you’re the kind of gun and history geek (hey! own it) we generally attract to the blog, you’re already familiar with the Krummlauf (“crooked barrel”) attachment to the German MP.44 series assault rifles.

The Krummlauf  is well-documented in books like Small Arms of the World, surviving period documents, and that sort of thing. It was made in several versions, differing in the degree of “bend” (30, 45, and 60º IIRC) and could be used for firing from cover (down), or the whole weapon could be turned over for firing around corners (sideways). It had its own 1.5x optic, and the extended, curved barrel was both vented for relief, and rifled.

Whether it was intended for urban warfare (firing around corners in the assault), armored warfare (firing from behind cover in a halftrack) or positional warfare (firing from trenches) is a matter of speculation. The problem with this kind of specialized weapon, for the Germans or anybody, is that you only need it once in a while, but you have to carry it all the time. That is, if you’re going to have any hope of having it with you on the rare occasion when you do need it.

There’s a number of surviving Krummlauf attachments and MP44 Krummlauf hosts, at least a half dozen, with at least two on the NFA registry (there are probably more that those numbers). One was auctioned recently by Rock Island and has a very complete description, with an explanatory video by Ian McCollum of Forgotten Weapons, on its auction page.

grease_gun_around_corners_ps_march_52The US experimented with something similar, but vastly simpler. We deleted the German prismatic sight, and didn’t even make a complete barrel, creating something more like a bullet trough for a spray of 230-grain solids to go off in the general direction of the enemy. This has been widely reported to have been done by the OSS. The historical writeups are thinner than on the Krummlauf, but they’re there. The gun seems to have first come to public attention in the Korean War era. For example, it was featured in Popular Science magazine in March, 1952 (image left). The article suggests that the gun was meant to be used, and hints that there might have been an optic, but, “Sights are secret.” The gun was also featured in LIFE in 1953, and those photos turn up online here and there.

LIFE OSS curved barrel

But we never knew until we stumbled over it on the excellent site, that there were at least two Russian variants of the same thing for the PPSh-41, which was made in staggering quantities. Unlike the common PPSh, these variations are extremely rare, probably for the same reasons of impracticality that limited distribution of the German and American ones. The more sophisticated showed a similar design approach to the Krummlauf, with the added benefit of being easily convertible in direction. This video shows the gun:


The second was a bent-down version, called in one reference the Model 1945, that looks more like a gimmick than a real, working gun.

ppsh-45 curved

It honestly looks like someone heated and bent a regular PPSh. (As we’ve seen from our recent M4 at Wanat series, heating barrels can be A Bad Thing®).


We’d love to have the whole who-shot-John on these, but we don’t. Maybe some commenters can help.

One of the most interesting questions is this: were the American and Russian “corner guns” simply examples of convergent evolution, or did they come about after examining German Krummlauf units?

Ian notes, in his video about the Krummlauf, that the Germans tried doing an open trough like the later American Grease Gun modification, but gave it up and went with a rifled curved bore instead.

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

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.

Continue reading

The Big Lie About Wanat (COP Kahler), Part 1 of 2 (long)

The Big Lie principle, as elaborated by Hitler and Goebbels, is that if you tell a small lie, you’ll be caught on it, but if you tell a really big, even outrageous whopper, people will tend to believe it. It’s an insight into human psychology which helps explain how those two second-stringers wound up seizing the levers of the most advanced nation in 20th Century Europe and running it into the ground, to the detriment of scores of millions worldwide. But right now, it’s making the rounds in our little world, as hired shills for foreign manufacturers lie about one battle to pad their own paychecks. This lie is so bold and blatant that many have come to accept it as true, even though official documents tell another story.

The lie is that, “9 American Infantrymen died on 13 July 08 at COP Kahler at Wanat, Afghanistan, in the Waygul Valley of Nuristan province, because their M4 Carbines jammed”. This lie clearly doesn’t hold up if you read the historical papers, professional analyses, and interviews with survivors. What does hold up is a story of incredible devotion, dedication and heroism on the part of the Americans there, and of intelligent, bold and fearless attacks on the part of their enemies. But there are some facts the foreign-firm lobbyists don’t tell you.

  • to start with, that they’re paid lobbyists.
  • Then, that most of the killed were not using M4s at the time they were killed.
  • Then, that those that were did not have jammed rifles.
  • Then, that the survivors who did have jammed rifles, used the rifles far beyond their duty cycle, because (1) they hadn’t been trained on the limits of the weapon and its duty cycle, but mostly, (2) they hadn’t any other option: their crew-served weapons went down due to failure, ammunition exhaustion, or destruction by accurate enemy MG and RPG fire, leaving them with ugly choices: go cyclic for long periods with rifles, or get defeated. Getting defeated was not a survivable option.
Indefensible: COP Kahler viewed from an aircraft, looking south. It is the tan area at center. COL Ostlund photo.

Indefensible: COP Kahler viewed from an aircraft, looking south. It is the tan area at center. COL Ostlund photo.

This was the plan to which COP Kahler was built. It was opened just days before the attack.

This was the plan to which COP Kahler was built. It was opened just days before the attack.

Why, then, does this story persist? It persists because it fits a narrative much beloved of the anti-military writers of the Acela Corridor, many of whom are unsophisticated and trivially spun by lobbyists. The Atlantic magazine is a fine illustration of this. In a recent article by a defense-industry lobbyist and retired general, whose conflicts of interest they have never disclosed, they printed:

The M4, the standard carbine in use by the infantry today, is a lighter version of the M16 rifle that killed so many of the soldiers who carried it in Vietnam. (The M16 is still also in wide use today.) In the early morning of July 13, 2008, nine infantrymen died fighting off a Taliban attack at a combat outpost near the village of Wanat in Afghanistan’s Nuristan province. Some of the soldiers present later reported that in the midst of battle their rifles overheated and jammed. The Wanat story is reminiscent of experiences in Vietnam: in fact, other than a few cosmetic changes, the rifles from both wars are virtually the same. And the M4’s shorter barrel makes it less effective at long ranges than the older M16—an especially serious disadvantage in modern combat, which is increasingly taking place over long ranges.

OK, perhaps in a future post we’ll break that out, bullshit by bullshit. For example:

  • The M4 is a lighter version of the M16 Rifle, yes, and the 2015 Corvette is a modified version of a car introduced in 1953. There are very few parts in an M4 that are the same as the ones this guy’s artillery battery struggled with at FSB Bertchesgaden almost 50 years ago. Most of those parts are in the trigger group, and there’s always the charging handle. Apart from those, from muzzle to buttstock, from sights to magazine, it’s a new gun.

But we’re not going to do that today. Instead we’re going to address this insidious and false claim:

  • [N]ine infantrymen died fighting off a Taliban attack at a combat outpost near the village of Wanat. So far, so good. (At least he notes that they did fight off the attack; a lot of careless reporters say they were overrun).
  • Some of the soldiers present later reported that in the midst of battle their rifles overheated and jammed. Yes. You see what the author is doing there? He’s making the inferences, without saying in so many words, that their guns killed them. This is one of those things that is “true, but….” Those grunts were not killed by their guns. They were killed by the enemy, and as we’ll see, the malfunction of weapons systems was real, but not decisive. You could argue that bad training, worse officer leadership in the planning phases (the officers provided magnificent leadership under fire), and incredibly-bad site selection were responsible, instead.  (The location selected for COP Kahler was the bottom of a bowl, with mountains about 7,000 feet higher surrounding the outpost 360º. It’s hard to imagine a less defensible position, yet these guys defended it). But in the end, they were infantrymen in a hard fight with a determined enemy, and guys get hurt doing that.

So let’s explore the action at Wanat for a minute. Click “More” to continue. This is a long one.

Continue reading

The M3 Medium Tank’s Fixed Machine Guns

Back in the Secondary Armament discussion, one of the commenters reminded us that early marks of the M3 Medium Tank had fixed forward-firing machine guns. That’s quite true.

This illustration shows the initial design layout for armament in the M3 Medium Tank.


There’s a sponson-mounted, 75mm M2 cannon, a high-velocity 37mm (called by the British a 2-pdr) which was still believed to be better medicine for enemy tanks (by 1941 it was already obsolete), no coaxial MG, a commander’s MG in a turret-on-a-turret (a recurring American design theme) and two  fixed forward-firing machine guns.

Like the wedding-cake turret stack, which returned to American tanks in the postwar M48 and M60 tanks (mostly out of NBC concerns), the forward-firing fixed MGs were once standard American design language. Britain and Russia had also built multi-turreted, landship-style tanks in the interwar years, but had given it up by 1941. But nobody else went all-in for fixed MGs.

While the idea of machine guns that the driver could aim by aiming the tank sounds a bit like the forward-firing guns that interrupter/synchronizer gears made possible on airplanes, the problem was that, unlike an airplane, a tank crawls in a 2-dimensional environment whose third dimension is dictated entirely by the terrain, making it impossible to aim the guns in elevation. Thus, they were nothing but useless noisemakers.

Making enough noise has never been a tanker’s problem.


Nonetheless, the US medium and light tanks of the interwar period all had a couple of fixed forward-firers, and these persisted into the M3 light tank (in the image above, you can see a ghosted MG, just left of drawing center; one was located in each sponson) and the M3 medium. They were often deleted in the field and not included in later production units of these tanks.

One of the It Seemed Like a Good Idea at the Time file.

The M3 Medium, an interim, stopgap tank, is remembered today largely for its failings and as a stepstone on the way to the superior all-round Sherman. Its suspension was noisy by tank standards, its riveted armor prone to launching rivets around the inside of the tank under fire, its very high profile rendered a hull-down position an impossibility and gave even the most nearsighted German a target he could scarcely miss. It had no fume extraction, so filled with toxic fumes during combat — there are plenty of pictures of British crews running the tanks and even fighting with the large side doors open, both for ventilation and because there was no other way to get rid of fired shell casings.

But when the first M3s arrived in the Western Desert, the British tankers loved them. It was significantly faster than any British tank, far more reliable mechanically (especially compared to the British Crusader tank), had a more powerful gun than any British tank, and had a large, comfortable (by 1942 tank standards), interior, with copious stowage space.

But they never did make use of those fixed machine guns.

Tank Secondary Armament Through the Years

While we’re talking tanks — we’ve recently covered armor protection in WWII and rates of turret traverse, and the technical considerations that went into them — let’s talk a little about secondary armament.

Most tanks have had, since the 1930s, a main gun that’s primarily designed to fire anti-tank ammunition, but is also capable of firing high-explosive general-purpose shells, and secondary armament of machine guns. This has come to be accepted as the norm, but it wasn’t always so.

The first tanks deployed by the British Army in 1915-16 were laid out differently from modern tanks. Their automotive equipment (a Ricardo engine and drivetrain) was contained with most of the crew between the tracks, which wrapped around the periphery of the lozenge-shaped tank. Armament was exiled to sponsons which hung off the sides of the tank, outboard of the tracks. These tanks came in “male” and “female” versions, which was defined by their armament. The “male” tank had a small artillery piece in the front of each sponson, and a machine gun in the rear; the “females” had machine-guns all around and were intended to provide support against close-in infantry for the male tanks.

Later, Germany’s first real production tank, the Panzer I, was armed only with machine guns (initially, 2 x MG.13, later 1 x MG.34), as were some inter-war light tanks of Britain, America and Russia, and even the first version of the US M2 Medium Tank, America’s most important inter-war tank. But at the war’s outbreak, and through to war’s end, most tanks were conceptually similar to modern tank: a main gun, a coaxial machine gun that shared the main gun’s aiming systems, and one or more guns atop the turret for antiaircraft use. (One thing WWII tanks almost all did have, which now almost no tanks have, is a bow machine gun aimed by a crewman sitting beside the driver. This gun station was deleted from postwar tanks worldwide).

Secondary Armament Trends as Illustrated by the US Example

The trend in the 1930s and 1940s was for fewer machine guns. This photo from Aberdeen Proving Ground’s museum shows what we believe to be one of only two surviving M2 Medium Tanks (an M2A1). Apart from its primitive, riveted hull of face-hardened armor (a weakness that would persist into the early models of its replacement, the M3), you can see four of its seven fixed machine gun positions in this view.



Each sponson, at the four corners of the fighting compartment, hosted an M1919 Browning machine gun. In addition, two more MGs were fixed to fire forward through the glacis — you see their places left and right of the national insignia. A co-ax in the turret brought the 1919 count to seven; with two AA machine guns added, which could be on the turret or firing through roof hatches in the main-hull fighting compartment, this late-1930s monstrosity could have nine MGs on board, plus the puny 37mm (1.5″) main gun.

Here’s an interior shot (from this page) of the back of the other surviving M2A1’s fighting compartment, showing the two aft sponson MGs, and one AA MG. These rear guns had a unique special-purpose application on the M2: they could be fired at 45-degree “bullet deflectors” above and behind the rear fenders, and would deflect the stream of bullets down — this was to help the tank to kill any infantry it rolled over in trenches.


Seven to nine machine guns are a lot of secondary armament, and one of the problems with that is that it required a large crew to run all the guns. The M2 required a crew of at least 6, although internet sources are all over the ballpark with claims from 4 to 9.

M3 with 6 of its crew in North Africa

M3 with 6 of its crew in North Africa

The M3 that replaced it (called “Grant” and “Lee” by the British, depending on which turret the tank had) had more firepower (a 75mm gun based on the old “French 75″ that was the cornerstone of American gunnery, set in a right-side superstructure sponson) and fewer machine guns (only 2, a co-ax in the 37mm turret and an MG in a small commander’s turret in US-turret versions or an AA/GP flexible gun with the British turret). It got by with a crew of 6 (UK) or 7 (US, adding a Radio Operator). And the M4, which had replaced the M3 by early 1944, went to war with only 3 machine guns (bow, co-ax, and AA/GP atop the turret) and a crew of 5.

There were real benefits to a smaller crew. These were primarily logistical. If you could save one man from a crew, you could get a bonus 16-20% more crews from the same number of recruits, and have to supply proportionally less water, food, and all items for which headcount is a cost driver, to any given number of tanks or tank units. But there is also a benefit in that a smaller crew makes for easier intracrew communication and coordination.


The colorful (if over-compressed in the copy) summer, 1941 propaganda video, The Tanks Are Coming, celebrates American tanks, and includes the M2 Medium; M2, and M3, Light tanks; and White armored scout cars. (Unfortunately, it’s too big a file to embed here, so we’ll just send you to the page).

Note at the 8 minute mark some of the simulators used to train tank gunners, including a sort of air-driven tommy gun and a “wobble platform” designed to make gunners proficient in firing the main armament from a tank moving cross-country. Later in the video, they show an incredible new vehicle, the “Blitz Buggy” — we’ve come to know it in the decades since as the Jeep!

You can see the M3 tank (in the version the British called the “Lee”) in the 1943 movie Sahara with Humphrey Bogart.

The Importance of Secondary Armament in Combat

While much of tank training and gunnery tables assume tank-versus-tank combat, much of armor strategy involves hitting the enemy with your tanks where his tanks are not. That’s where secondary armament comes to the fore. Machine guns are necessary in this tank-vs-enemy-logistical-trains and rear-echelon-units warfare; they are what takes a tank breakthrough of the enemy’s hard-shell combat line and turn it into a rout.

The next most important use of the secondary armament is in tank-vs-tank or combined arms combat, in keeping hunter-killer groups of infantry of one’s own and one’s unit’s tanks. In the Pacific, for example, both Japanese and American tanks were more likely to be lost to infantry attacks than to tanks or dedicated anti-tank artillery. Infantry methods of tank-killing ranged from prying a hatch open and shooting the crew to, later in the war, specially developed infantry anti-tank weapons with hollow-charge warheads.

Finally, the armor branch, perhaps because they are a more-technical crowd, less shy of innovation than the tradition-bound infantry, have been a proving ground for new machine-gun concepts over the years. Some, like the US M73 and M219, were complete failures, as was the attempt to adapt the M60 to tank use. But the M1 tank’s adoption of the superior M240 machine gun laid the groundwork for that gun to replace the M60 for the infantry, for which blessing every grunt ought to buy the next tanker he meets a beer.