Category Archives: Weapons Technology

VPO-208: Russian Gunsmiths Respond to Russian Law

We’re familiar, here in the USA, with weapons that are shaped by US gun laws. We have a variety of weird and wonderful arms that exist only because of the Gun Control Act of 1968, the National Firearms Act of 1934, and the patchwork of implementing regulations and executive orders that have shaped the US market. In addition, state assault-weapon band have resulted in oddities like California’s “Bullet Buttons.” A wide range of legislatively-midwifed Frankenguns, from the Walther PPK/S, to short barreled rifles, to pistols with SIG braces, reflect the degree to which designers are constrained by the gun-designing impulses of American politicians and bureaucrats.

It should come as no surprise that the same thing happens in other countries with large gun markets. This case in point comes to us from Russia, where gun laws are generally stricter than in the United States. There, no one can own a pistol. Most citizens can own a shotgun; but to own a rifle you have to have owned the shotgun without incident for five years.

So here comes the VPO-208: an SKS shotgun.

SKS in .366Produced by Techcrim, an Izhevsk manufacturer, the .366 by Russian measure, across the lands (.375 by ours, across the grooves), is a smoothbore or near-smoothbore gun that gets the would-be gun owner into a semi-automatic, service rifle platform, while staying within the letters of Russian law.

The ammunition appears to be made from fireformed 7.62 x 39mm casings, and is available in a range of sporting projectiles, plus a shotshell variant.

It is reminiscent of such American wildcats (some of them since turned production) as the small-head .300 Whisper, .300 AAC Blackout, .338 Spectre, and the Mauser-head-sized .375 Reaper, all of which run in the AR-15 platform. It just goes to show that this kind of innovation is hardly an American monopoly.

The first table in the advert below has three columns: “Type of projectile”; “Speed, meters per second;” and “Energy, Joules”. Here’s our conversion of this table.

Projectile Type Velocity, m/s Energy, J Velocity, fps Energy, ft-lb
LSWC poly coat 13.5 grams 640 2765 2099 2039
FMJ 11 grams 700 2618 2296 1931
FMJ 15 grams 620 2883 2034 2126
JSP 15 grams 620 2883 2034 2126



As the shot of the fired JSP shows, and these velocity and energy tables suggest, it would actually be a good short-range hunting round.

The second table, with the bullet-drop diagram, is, “Velocity and Energy of Projectile, .366 TKM with 15-gram FMJ bullet”. Here’s our translation and unit conversion.

Metric (SI) Values Muzzle 50 meters 100 meters
Bullet Drop mm 0 35 125
Velocity m/s 625 570 520
Energy J 2837 2437 2028
English Values Muzzle 50m 100m
Bullet Drop in. 0 1.38 4.92
Velocity f/s 2050 1870 1706
Energy ft/lb. 2092 1797 1495

The problem with the gun is its accuracy, as it’s basically a smoothbore. Hyperprapor suggests that it might be minute-of-E-silhouette at 100m.

But hey, it will let some Russian guys own the rifle their nation’s color guards parade with, and even let them shoot it, all with the reduced paperwork and hassle of a shotgun; perhaps a big win for them.

There are no ballistics for the shotshell, which exists, we suspect, primarily to navigate the channels of Russian weapons law. (This law does seem somewhat liberalized since Soviet days). Techcrim’s website shows that they are very active in small-caliber (.410) shotguns and shells, which seem to have more of a following in Russia than they do here. We wonder if that’s an artifact of Russian law, too.

We saw this on r/guns, posted by our old friend hyperprapor, who notes that under Russian law “paradox rifling”  is legal if it’s under 150mm long (About 5.9″).  Paradox rifling is rifling that was just engraved in the last few inches of the bore of what was otherwise a shotgun, to give it some capability with a single ball or bullet. It was named by English bespoke gunmaker Holland and Holland, who adopted the patent from GV Fosbery of Webley-Fosbery fame. Westley Richards called it “Explora” but other makers seem to have stuck with the paradox name.

And this is definitely one for the “how weird does it get” file — a smoothbore SKS that is one short hop removed from the Webley-Fosbery Automatic Revolver!

You can’t drill a #40 hole with a #40.7 or so Drill

OK, not gunsmithing here, but planesmithing. And something has been going wrong for a while, but we were too blind to see it.

bent drill bit

The first phase of building a RV-12 involves drilling a lot of holes. It’s not arduous; many of the holes are already drilled in the parts, although undersize; hundreds need to be finish-drilled to size; some parts need to be clecoed together and match-drilled so there’s zero relative movement when they’re riveted together; a few holes need to made in virgin metal. Once the holes are drilled, they need to be deburred (we use a single-flute deburring tool) and some of them need to be countersunk for flush rivets. (Some, in thin sheet metal, are dimpled instead of countersunk).

In the tail section, relatively few drills are used. Because the AN rivets and pulled rivets are expressed in fractional sizes, most of the holes are drilled with numbered drills, and the ones that got a workout were #12, #30 and #40. (Drill gauge is like shotgun gauge: larger numbers are smaller diameters). For instance, the right hole for a 3/32″ rivet (0.09375″) is not a 3/32 (no clearance), but a #40 (0.098) gives you about four thousandths for clearance — and tolerances.

We found making holes to be easy, but there were a lot of frustrations when it came to using those holes. We couldn’t get the countersink’s pilot in the hole all the time (we wound up using an unpiloted countersink). Clecos, the small spring-loaded pins used to temporarily join sheet metal destined to be riveted, didn’t always go. Some of this is tolerance in the Clecos, and we through some troublesome ones away. (You can never have too many Clecos when building an aluminum airplane, but bad tools need banishing or they just cause trouble). Then, when it came to riviting… the rivets didn’t fit. It was hard to fit them in. When we did, the friction was so heavy it was hard to form good heads.

On the bright side, we got some practice at drilling out rivets. So there was that.

Last night, we had an epiphany. So many of our holes were undersized, yet, you could slip the drill bit right through no problem, so we hadn’t made the holes with the wrong bits or anything like that. But we had always been using our new Hertel drill bits, the same ones we made the holes with, as measuring tool. We took up an older #30 and tried to slip it into the hole the new #30 had made, because the AN rivet spec’d for the hole wouldn’t go.

Neither would the older #30 bit. Oh, crap, were our new, high-quality drill bits undersized?

We didn’t want to think so. Therefore, we measured all three of the ones we’d used a lot.

Drill Bit Nominal size Measured size ∆ size
# 12 0.1890 0.1890 0.0000
# 30 0.1289 0.1170 0.0119
# 40 0.0980 0.0940 0.0040

(Note, we’re not claiming that our digital caliper technique is accurate to four decimal points. We just added zeroes where needed to make everything line up).

The bad news: we’re going to have to redrill every freaking #30 hole, and some of the #40s as well. (If a rivet test-fits without pressure, we know we’re good). The drill bits were actually undersized, #40 by four thousandths, and more than one hundredth.

They didn’t get that way from us using them — we’re not cutting anything but sheet 2024 aluminum alloy.

The good news: we now know why we were bedeviled by non-fitting rivets.

The moral of the story: from now on, test drill and check for size using a gage pin, every time we change sets of drill bits.

The company that made the drills is Hertel, and it was a quality (and pricy) set. The supplier was MSC. It will be interesting to see what happens when we call them with this problem.

G36: A Debacle, in a Fiasco, Wrapped in a Clusterbleep

The G36 saga keeps spreading its Sturm und Drang around the fraught world of German politics.

Our good friend Nathaniel at the Firearm Blog flagged us to a Deutsche Welle report that reminded us that there have been a lot more developments in this Neverending Story. BLUF: none of those developments suggest a rapid fix for the real problem with the rifle, no more do they suggest a way to restore lost soldier confidence in the rifle, and instead they show a military-technical problem becoming a political football. And the game is world, not North American, football, which ensures it will get kicked around a lot before it gets in the goal — if it ever gets in the goal.

Here’s video from the fight that started the whole controversy:

There are several different firefights represented in that video. But near the end of the video, the narrator mentions that the men of “Golf” platoon have been in a running firefight for 9 hours. And then, as they are withdrawing under pressure, a vehicle is struck by an IED. And “several rifles fail due to overheating.”

For all that, we don’t have audio of a lot of rifles firing on full-auto. Instead, we hear single shots and occasional short, controlled, bursts, and the longer, extremely fast bursts of the high-cyclic-rate MG3 (improved MG42). We hear enough to know that these men from the 313th Parachute Infantry Battalion are stone pros. But that’s where the problems began, back in 2010: the troops began to notice that their rifles were underperforming.

Tests, which leaders probably expected to put the modern Landsers’ complaints to rest, began to bear the troop complaints out. If the barrel was heated cherry-red, accuracy declined. Two magazines on rapid semiauto fire? Accuracy declined. If the outside air temperature was more than 23ºC at sea level (about 77ºF), not very high at all, accuracy declined. HK responds: “Hey, that wasn’t the standard we had to meet with the gun, that wasn’t the original test.” True enough, as far as it goes, but that doesn’t make the rifle combat-worthy. How much does accuracy decline? Here’s a handy graphic from Reuters via DW. At 600m, at 30º, instead of hitting an enemy in the window of a building, you might hit the building:

G36 temperature-related failure

Even at 200m, your dispersion is looking like a meter in diameter. (30ºC is about 90ºF, quite a high temperature for Europe).

The German magazine Der Spiegel (“Mirror”) has been all over this. This link should search Spiegel for “G36″ (results in German, selbstverständlich).  Here are some of the results:

At First, it Was About the Gun…

18 April 15: H&K Defends the Breakdown Rifle (which only partially gets the degree to which the neologism Pannengewehr is a putdown of the company and the firearm). HK’s majority owner Andreas Heeschen told a newspaper “Anything we make is 100% combat-ready.” On the same day (different story), Spiegel reported that H&K itself conducts the official proof tests and applies the official marks itself (which is probably not the departure from the norm that the magazine’s writers think). The responsible agency, the Bundesamt für Wehrtechnik und Beschaffung (BWB), had delegated this authority to H&K based on past performance. Again, on the same date, the MOD reiterated that the rifle was only provisionally suited for use (another Spiegel story, same date), and that it “endangered the lives of German soldiers.”

Apart from HK’s bluster and threats of lawsuits, the only positive G36 story appearing in Spiegel came the next day, suggesting that the Kurds liked it, at least. And Lithuania and Latvia appear to be satisfied with their G36 purchases.

“With us there has been no trace of technical problems with the G36. On the contrary: the weapon is super”, Pesh Merga Minister Mustafa Sajid Kadir said. “It works without problems. We’d gladly have more of them.” Last year the Bundeswehr gave the Kurds, along with other weapons, 8000 G36 rifles for their fight against the “Islamic State” terrorist militia.

According to the Latvian Defense Ministry, the model used their is “significantly” different from the German variant. A spokeswoman said that there had been no problems in quite a long time..

Also, in neighboring Lithuania the affair in Germany is not in the news. The military command are “aware that there other nations have been confronted with problems with the accuracy and the robustness of certain parts of the G3, said Major General Jonas Vytautas Zukas, commander of the Lithuanian Army. But there is no thought of backing off from the rifle for that reason. Much more there are plans to order additional G36s. “These weapons meet the requirements of the Lithuanian Army.”

The Defense Minister moved decisively on 22 April when she said that the G36, as currently configured, had “no future in the Bundeswehr.

But Soon, it was About the Cover-Up

As it became clearer that the initial heads-up about G36 problems came from a series of firefights by German paras based in the Provincial Reconstruction Team in Mazar-e Sharif in north central Afghanistan in 2010, and the technical verdict on the problem was largely in during 2012, the political fallout began to raise a noise level that drowned out the voices calling for a technical fix.

Spiegel found that in 2010 and 2011, the German Special Forces Command KommandoSpezialKräfte (KSK) were already looking for a G36 replacement that would be accurate to 300m and capable of selective fire. They didn’t call it a G36 replacement, instead terming it a “close range sharpshooter rifle,” but the weapons tested tell the story: HK 416, SIG 516, Schmeisser Solid and one unnamed competitor. It was a small contract: 5,000 rifles. Spiegel writes, “Insiders suspect that the competition concealed a Ministry of Defense search for a G36 replacement.” But Spiegel can’t have it both ways: was the MOD clueless, or was it scheming? It’s illogical to suggest it was both, which the magazine at least has the decency to avoid by putting the two speculations in different stories.

Various politicians in Germany were calling for the head of Thomas de la Maizière, the Defense Minister on whose watch the problem should have surfaced, but seemed to be covered up. Others pointed to the incumbent, de la Maizière’s party colleague and replacement at MOD Ursula von der Leyen, as the necessary sacrifice. Indeed, by 20 April, days before her pronouncement that the G36 had “no future,” Spiegel was contrasting her high hopes at her swearing-in to the way the chaos of the G36 affair threatened her political career, perhaps not by getting her fired now, but by blocking any further advancement for the ambitious politician.

Competing leaks have pinned responsibility for the cover-up on de la Maizière and on von der Leyen. They describe the accuracy problem various ways: “twice as bad, three times as bad” or, chillingly, noting that with the issue firearm and ammunition combination, “a hit at combat range is not possible.”  One German politician spoke up as the voice of fiscal sobriety:

In almost every armaments scandal we see the same picture: bad material was bought expensively, no one is responsible in the end, and the taxpayers have to pay.

The finance hawk? Jan van Aken of Die Linke, the rump vestige of East Germany’s communist Quislings. Van Aken is a member of the legislature’s Defense Committee.

The most recent, and damaging, release is that a former MOD official sicced a military intelligence agency on the leakers and the reporters they leak to. The Militärabschirmdienst (MAD), or Military Protective Service, is a counterintelligence agency of the Bundeswehr. The MAD appears to have drafted a plan to defend the G36, the Ministry, and HK by going on clandestine propaganda offensive against press critics. The plan was never approved, and the head of MAD transferred laterally to another job, but the scent of the problem has drawn more opposition sharks.

None of this inside-Berlin political drama has any prospect of restoring either German soldiers’ confidence in their individual weapon, or equipping them with an individual weapon in which they can have confidence. But von der Leyen will have to take measures in that direction soon. Or she will have a successor who will.

At least the Germans have alternatives. India recently gave up on the equally problematical (in different ways) home-grown INSAS rifle, and really had nothing to offer its frontline troops but old AK-47s.

Can This Gun be Saved?

This classic old Colt Mustang .380, the original Colt knockoff of the Llama pocket-pistol knockoff of the 1911, has seen better days. Can it be saved? A customer brought it to a gunsmith who told the story on Reddit and Imgur (all these photos came from Imgur, and are linked in the Reddit thread).

Colt Mustang Before

The old Colt is still functional enough, but it’s fugly. The steel slide and barrel are pitted. The alloy frame is also corroded, and the trigger guard, integral to the frame, is nicked and generally chewed-up looking.  Can it look like new again? Click “more” to see!

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Lee Williams: Down With Poly AK Mags!

Lee Williams has had it with polymer AK mags, and this is his reason:

The mag blew up while sitting unattended in Lee’s safe, and the resulting chaos was waiting for him when he opened it up.

I’m done with polymer AK mags
Posted on April 30, 2015 by Lee Williams

I had a surprise last night when I opened my safe.

The top of a loaded polymer AK mag had broken off for reasons unknown, spraying 28 loaded rounds and bits of plastic all over my safe.

The spring was sticking halfway out of the top of the mag. I found the follower behind an SKS.

via I’m done with polymer AK mags – The Gun Writer.

We agree that this is an unhappy thing. We don’t agree that all polymer mags are created equal. (Ask any Glock owner who’s tried both Glock mags and the temptingly cheap Korean knock-offs). Even all polymer AK mags.

The Russians were the first to issue a synthetic magazine widely, and in the 1970s began producing polymer magazines with reinforcements in critical areas for the AKM and AK-74 rifles. These are the characteristic orange mags. They’re a good bit heavier than modern polymer mags, a lot heavier than US or Western-style aluminum or even steel mags, but are a lot heavier than thick-sheet Russian AK mags. Ivan’s polymer/steel composite-construction mags are about as durable as the steel mags they replaced (and significantly lighter). Collectors call these “Bakelite” mags, but the material does not appear to be Bakelite at all — it’s some other form of thermosetting; a Finnish article reprinted on a US site, minus most of its original photos unfortunately, says that it’s “fiber-reinforced phenol.” (We wonder if that’s a mistranslation that should have been phenolic instead).

To our disappointment, an unclas tech intel bulletin on the mags that we know was out there, was not available on DTIC. There is an interesting page on the net that lays out various mags for 5.45mm-class weapons, and some of that transfers to the 7.62mm versions. Anyway, we haven’t brought one of these mags to our injection-molding expert friend, but the original kind of feels like urea plastic to us. The Circle-10s are something lighter, maybe even ABS (ordinary polystyrene, like in hard-plastic toys).

The mag that disassembled itself on Lee was indeed a Bulgarian “Circle-10″ mag, a marking associated with Arsenal, and as you can see, it is by design not reinforced, neither with steel lips nor fiber reinforcement.

What makes a mag fail like this? Lee seems to think that the guilty party is leaving the mag loaded for a length of time. We have our doubts about that and would be more inclined to suspect the cumulative effects of age and ultraviolet-ray exposure (plain ordinary sunlight, which it certainly couldn’t have gotten in his safe). But the durability of different AK mags, even different Bulgarian mags, is widely variable.

We also don’t think loading only 28 rounds buys you anything. The difference in pressure is nominal. This goes back at least as far as Vietnam and was a ritual practiced by troops (although, there it was putting 18 rounds in a 20-round magazine) who were neither trained on the rifle nor given a supply of replacement magazines. It was something they did to appease the M16 Gods

The plain ugly fact is that magazines are, by design, expendable items and you need to start thinking of them that way — they’re the toilet-paper of small arms, necessary but not especially durable or reusable. And just like toilet paper, some brands are better than others. Lee, for example, probably should dump all of his circle-10s that are the same age as the one that failed, because their clock is ticking, too. Sorry to be The Bear of Bad News.

In the real world, private owners and armies alike are reluctant to purge their bad magazines because the mags represent a considerable cost — both the sunk cost that was spent on them and is lost for good, and (more germanely) the replacement cost for new mags. It is possible (although not necessarily economical or practical) to repair or overhaul metal, especially steel, magazines, but synthetic materials are harder to repair and rebuild.

How Cool is This? 3D Roundup May 2015

Decisons, Decisions

Art, meet Science: 3D printed fixtures made on the Mark One supports precision assembly of this French horn.

Art, meet Science: 3D printed fixtures made on the Mark One support precision assembly of this French horn. Lots of cool applications on the MarkForged website.

So… our Mark One 3D printer may be ten to twelve weeks coming, because the company’s so backed-up. But if you’re willing to help them with a case study, they’ll bump you up in the line. Problem is, one of our initial prints is sensitive DOD stuff; others are promised to third parties, and we can’t release info w/o their approval. But overall, the big problem is that we don’t know what we’re doing with the machine yet. We’re buying it for the sheer hell of exploring what we can do with it. Kind of figuring the machine itself will define the application. Yes, it’s a leap of faith — faith in technology, human ingenuity (not least, our own), and the future. Leap with us!

Parts with Intel Inside?

voxel8 printerOne of the cool things about the MarkOne is that you can interrupt printing to put an internal part inside, and then resume the print. We can think of all kinds of things we’d like to embed in a polymer part: bearings, threaded inserts, strain gages. Now a startup named Voxel8 has come up with printable conductive traces that can be embedded in the very material of a part (and their printer, too, is interruptable so that you can embed a mechanical part. Ordinary 3D printers can’t allow this). For some details of how it works, see MIT Technology Review, again. The Voxel8 printer is available for pre-order now ($9k upfront for the developer kit; $500 now and $8500 pre-shipping just for a place in line). One of the researchers whose science this is based on, Jennifer Lewis, has moved on to multi-material nanoscale printing, to give you an idea where this is going. Her team has printed batteries, which boggles this decidedly sub-Harvard mind; and one of those links shows her with an elastomeric glove with wires embedded in it (a wider range of polymers is something everybody is working on — low-hanging fruit for parts with better properties). Other teams pursuing similar technologies have printed, we are not making this up, retinal tissue, and one of the near-term applications may be ethical human tissues for medical testing, which might have advantages over common animal models.

PLA printed part with chip and printed silver leads.

PLA printed part with IC and printed silver leads.

Scaling back to the initial Voxel8, what could you do with this? Just sticking to the defense world, how ’bout low-cost, zero-ionizing-radiation, dependable night sights? How about something DOD is desperately jonesing for, a round counter? How about a thermocouple that warns an operator to slow down his rate of fire if at all possible, to preserve his firearm? What about strain gages literally embedded in parts? The Voxel8 will come with access to Autodesk Project Wire software for designing devices that give a whole new meaning to a two-word phrase that has a different meaning right now: integrated circuit. If we were Voxel8’s marketing wallah, we’d call it organic circuit, and trademark the term.

We want one of these badly, but we already have $9k tied up waiting for another 3D Printer. Hey, Voxel8, what’s “organic circuit®” worth to ya?

Nothing to do with Our Industry, but…

How cool is this? Doctors dealing with kids with a congenital and, if severe, fatal deformity of the trachea and bronchi, tracheobronchomalacia, TBM, (Rangers, think of them like the intake manifold for your lungs) first used 3D printing to model the infants’ airways, no bigger than the lead in your #2 pencil, for surgery. But University of Michigan Med School associate prof Gerald Green came up with a better use for 3D printing — making a splint, or stent, that held the baby’s airway open so the TBM can’t suffocate him. If the kids can live through infancy, they can outgrow the condition.

The stents are customized to wrap around each kids’s individual bronchus or trachea and are inserted surgically, as we understand it. They hold the airway open so the little guy can breathe, and they actually expand as the baby grows to toddlerhood, and by being printed with bioresorbable material are gradually dissolved into the healthy child’s tissues so that they do not inhibit further growth.

Prediction: if Michigan doesn’t tenure Dr Green stat, he and maybe his whole team are going to be in a shiny new lab at a big, prestigious med school somewhere else. This saves very few lives — TBM is rare, especially at life-threatening levels — but it does save lives.

Plain-English overview at MIT Tech Review again. Here’s the conclusion and the abstract of his paper (you can’t read the paper for a year with a free subscription to Science, which we truly recommend, but if you or your library has a paid subscription with the American Academy for the Advancement of Science, you can read it now).

We implanted patient-specific 3D-printed external airway splints in three infants with severe TBM. At the time of publication, these infants no longer exhibited life-threatening airway disease and had demonstrated resolution of both pulmonary and extrapulmonary complications of their TBM. Long-term data show continued growth of the primary airways. This process has broad application for medical manufacturing of patient-specific 3D-printed devices that adjust to tissue growth through designed mechanical and degradation behaviors over time.

To print is to cure. How cool is that?

Meanwhile, while we’re digressing about medical 3DP, this one has meaning for the retired SF and SOF world, who all share one thing: aching knees. A team of Columbia scientists, Cornell vets, and Hospital for Special Surgery orthopods have printed a 3D scaffold of human meniscus cartilage, grew animal cartilage with endogenous stem cells, and implanted a complete, built-to-fit and biologically autologous (rejection-proof) meniscus in an animal model. We humans could be next, if the research continues to go well — and the FDA (Frustration of Doctors Administration) gets their finger out.

Science fiction fans, what can implantable, either permanent or bioresorbable as needed, structural things do for (or to, if you incline to dystopia) humanity?

Hell yes, we live in the future.

Better Parts, Faster?

We might have mentioned this one before. A firm called Carbon3D, using technology developed by research profs at North Carolina State University (NCSU) and the University of North Carolina (UNC), that amounts to continuous (not one-layer-at-a-time) stereolithography. They use oxygen as an inhibiting layer. Clever!

There are a few more details in this March story from MIT Technology Review, and of course at Carbon3D’s website. (There’s also a peer-reviewed paper in Science, which is accessible — thanks to a request of the authors — with the free registration).

They say their system, which they call CLIP (Continuous Liquid Interface Production), not only is orders of magnitude faster than extant technologies, but produces parts with superior finish and mechanical properties — parts the equal of injection-molded parts, but capable of being made in all polymers, including elastomers.

(A) Micropaddles with stems 50 μm in diameter. (B) Eiffel Tower model, 10 cm tall. (C) A shoe cleat >20 cm in length. Even in large parts, fine detail is achieved, as shown in the inset of (B) where features <1 mm in size are obtained. The micropaddles were printed at 25 mm/hour; the Eiffel Tower model and shoe cleat were printed at 100 mm/hour.

Parts printed with CLIP show superior detail and surface finish. Click to embiggen.

So that’s the benefit of this technology — it’s faster, and more versatile. As the image (Fig. 4 from their paper in Science) shows, it can produce excellent detail and surface finish, without the layering so commonly seen in FFF (Fused Filament Fabrication) and other common 3DP technologies.

The original caption, which doesn’t fit in WordPress’s caption ghetto, was:

(A) Micropaddles with stems 50 μm in diameter. (B) Eiffel Tower model, 10 cm tall. (C) A shoe cleat >20 cm in length. Even in large parts, fine detail is achieved, as shown in the inset of (B) where features <1 mm in size are obtained. The micropaddles were printed at 25 mm/hour; the Eiffel Tower model and shoe cleat were printed at 100 mm/hour.

We haven’t seen what sort of price point this will be coming in at, yet. But imagine its benefits for firearm personalization alone. Consider an autopistol backstrap or revolver grip that fits the anatomy of your hand perfectly, is made to the firmness you prefer, like a Sleep Number bed, and is printed for you in a machine in your LGS where you grip a sensor that “feels” your grip and then the machine runs off your perfect grip, in your choice of texture and color, while you wait. That’s just one example of the mass personalization that this makes possible. For instance, have you ever wished the windshield-washer stalk was an inch or two longer in a car? A dealer with technology like this could fit your Toyota or Ford to you while you were doing the paperwork. Anyone else could drive it, but all the controls would be subtly personalized to increase comfort, control and safety when you’re at the wheel.

What will they think of next? We don’t know, but we’re eager to see!

Twist Rate Affects Ballistic Coefficient

Bryan Litz with, once again, some science that makes our hair hurt, and that’s even in his cut-down version with minimal traumatic math. In a post excerpted from his latest book, Modern Advancements in Long Range Shooting, Litz discusses the results of tests with a rifle and a series of barrels manufactured by the same barrelsmith to differ only in twist rate, and be identical in all other aspects — a controlled experiment.

The Litz Lab -- a precision rifle with a set of barrels differing by only a single variable.

The Litz Lab — a precision rifle with a set of barrels differing by only a single variable.

Through our testing, we’ve learned that adequate spin-stabilization is important to achieving the best BC (and lowest drag). In other words, if you don’t spin your bullets fast enough (with sufficient twist rate), the BC of your bullets may be less than optimal. That means, in practical terms, that your bullets drop more quickly and deflect more in the wind (other factors being equal). Spin your bullets faster, and you can optimize your BC for best performance.

Any test that’s designed to study BC effects has to be carefully controlled in the sense that the variables are isolated. To this end, barrels were ordered from a single barrel smith, chambered and headspaced to the same rifle, with the only difference being the twist rate of the barrels. In this test, 3 pairs of barrels were used. In .224 caliber, 1:9” and 1:7” twist. In .243 caliber it was 1:10” and 1:8”, and in .30 caliber it was 1:12” and 1:10”. Other than the twist rates, each pair of barrels was identical in length, contour, and had similar round counts.

There’s quite a lot to get your skull around here, and even when you Read The Whole Thing™ (which you’re totally gonna do, right?) there’s stuff that’s hard to understand.

It led to quite a lot of barrels to keep organized!

It led to quite a lot of barrels to keep organized!

We wonder what the mechanism is that, in effect, raises the drag (and BC) of an underspun bullet, and what we think it is is a form of precession. Instead of spinning perfectly around its longitudinal axis, the bullet wobbles a little bit off axis. Instead of going along a perfect line, and therefore staying in a single point, as viewed in 2D from dead ahead, the point of the bullet is describing, when reduced to two dimensions, a small circle… in three dimensions, the point is spiraling towards the target even as the bullet’s center of mass is proceeding directly targetwards. There are several ways that this could raise the drag of a typically supersonic bullet. One is simply that the off-axis bullet may present a larger frontal area (or larger average frontal area, if the precessing bullet has a changing frontal area) to the slipstream. Another is that flow might separate irregularly from the tail of the bullet. Turbulent, separated flow induces buckets of drag. There are probably others that we don’t get because, unlike Bryan Litz, we’re not aerodynamicists by training.

Linearity of the results is striking.

Linearity of the results is striking. A 0.87 correlation quotient is an extremely solid result. 

One thing that Litz points out is that you may be getting very satisfactory groups, and still not optimum BC. Why does that matter? If your groups are OK and your BC is suboptimum, who cares? Well, BC (as Litz shows, practically a function of gyroscopic stability) also influences accurate range, for example.

It’s a common assumption that if a shooter is seeing great groups and round holes, that he’s seeing the full potential BC of the bullets. These tests did not support that assumption. It’s quite common to shoot very tight groups and have round bullet holes while your BC is compromised by as much as 10% or more. This is probably the most practical and important take-away from this test.

Like all of Litz’s research, this is some fascinating stuff. The same series of tests also showed that twist rate affects muzzle velocity, but very little. It’s intuitive that a higher twist rate would, by imparting more friction to the projectile, decrease muzzle velocity. The results, though, showed that while twist rate affects MV a statistically significant amount, that amount is extremely low. As Litz puts it, himself, in a couple of  the comments to the post:

The scatter in the data and the R squared value indicate that only about 1/2 the variation in MV is due to twist rate (Correlation Coefficient is 0.55) which means that random noise has as much effect as twist rate. This is discussed further in the book, as well as similar results presented for a different bullet in which the relationship was even weaker, and the correlation was lower.

Remember that the correlation quotient between twist rate and BC was 0.87. Random chance probability is 0.50, so unlike the twist-to-BC correlation, the twist-to-MV correlation is weak as water… but it’s still there. It’s a measure of Bryan Litz’s painstaking care in collecting this data that the 0.55 correlation even shows up in the data table, but it does, as a low double-digit variation in MV with each change in twist rate!

Linear, but barely perceptible, results. Amazing.

Linear, but barely perceptible, results. Amazing. As Litz notes, the experimental variation is smaller than the SD of the individual data points — if the relationship weren’t completely linear it would probably be invisible. It only shows up on the chart because of the suppressed zero value on the scale. 

The point in presenting these results is to show that the effect of twist rate on MV is VERY minor, and can almost be said to be statistically “in the noise”. ….

The long and short of it is that regardless of caliber and bullet weight, twist rate has very little effect on MV. You’ll see more fps difference per inch of twist on a .220 Swift just because you’re dealing with higher velocities. In other words, the percentage of MV change due to twist is pretty consistent.

That’s an example of how the comments are as good as a second, followup post in terms of their educational value. If you had asked us, we’d have said that, so long as the bullet was stabilized at some minimum level, twist rate would have had a minimal effect on accuracy, but a larger one on MV. And yet Bryan Litz’s results are exactly the opposite of what we’d have said on instinct. Obviously we didn’t understand this as well as we thought!

So read the post and comments — and keep reading till you understand it all, which may take those of us who are reformed infantrymen more than one reading. And if you want a deeper dive in the physics of accuracy, Modern Advancements in Long Range Shooting, and Litz’s other books are available from Applied Ballistics directly or from (at a glance, it looks like you save money by going to Applied Ballistics).

What’s After Tracking Point?

We’ve been pretty high on precision guided weapons technology since the first time we saw a TOW do its thing. (And Javelin and other current weapons have answered most of the complaints about TOW since then). But in recent years, the promise of PGWs has migrated down into the small arms world, thanks to the same combination of Moore’s Law, free-flying science and nitty-gritty engineering that gives us everything from rapid genome sequencing to haptics and 3D printing.

We’ve been pretty impressed with the precision-guided rifles and Tag / Track / XACT technology of Tracking Point. So what comes after that? DARPA says: precision-guided, steerable bullets. They call the program, in a felicitous acronym, EXACTO, Extreme Accuracy Tasked Ordnance. Like the Javelin and the Tracking Point PGW, it seems to tag a target and then pursue it relentlessly.

DARPA recently released the above video, along with this blurb:

DARPA’s Extreme Accuracy Tasked Ordnance (EXACTO) program, which developed a self-steering bullet to increase hit rates for difficult, long-distance shots, completed in February its most successful round of live-fire tests to date. An experienced shooter using the technology demonstration system repeatedly hit moving and evading targets. Additionally, a novice shooter using the system for the first time hit a moving target.

This is not too different from what TrackingPoint does now, in terms of results. What is different is how the EXACTO round functions.

This video shows EXACTO rounds maneuvering in flight to hit targets that are moving and accelerating. EXACTO’s specially designed ammunition and real-time optical guidance system help track and direct projectiles to their targets by compensating for weather, wind, target movement and other factors that can impede successful hits.

You can see from the video that they’re getting hits on their e-type silhouette, but they don’t appear to be getting center of mass hits. Still, it’s an admirable case of the dog walking on his hind legs, and this suggests that the science is licked, and what remains from here on out is simply engineering. (Not trivial, engineering, but once the science has shown that something is possible, it’s up to the engineers to find elegant and practical ways of doing it).

One significant difference between this and Tracking Point’s technology (so far) is that TP uses a bespoke or customized weapon; according to DARPA, EXACTO works with an ordinary rifle, only the optoelectronics and ammunition are changed.

It’s not rifle-caliber, as usually designated, yet; this demo is with a .50 caliber smart projectile.

“True to DARPA’s mission, EXACTO has demonstrated what was once thought impossible: the continuous guidance of a small-caliber bullet to target,” said Jerome Dunn, DARPA program manager. “This live-fire demonstration from a standard rifle showed that EXACTO is able to hit moving and evading targets with extreme accuracy at sniper ranges unachievable with traditional rounds. Fitting EXACTO’s guidance capabilities into a small .50-caliber size is a major breakthrough and opens the door to what could be possible in future guided projectiles across all calibers.”

The EXACTO program developed new approaches and advanced capabilities to improve the range and accuracy of sniper systems beyond the current state of the art. The program sought to improve sniper effectiveness and enhance troop safety by allowing greater shooter standoff range and reduction in target engagement timelines. For more information, please visit the program page.

via 2015/04/27 EXACTO Guided Bullet Demonstrates Repeatable Performance against Moving Targets.

OK, so let’s visit the program page, shall we?

Turns out, there’s not all that much there. We do get an uninformative 3D rendering of an EXACTO projectile, but that’s about it. There is a suggestion that the steering of the bullet is aerodynamic in principle.

exacto projectile_fullThere is this brief update on where the project stands:

The EXACTO 50- caliber round and optical sighting technology was developed to greatly extend the day and nighttime range over current state-of-the-art sniper systems. The system combined a maneuverable bullet and a real-time guidance system to track and deliver the projectile to the target, allowing the bullet to change path during flight to compensate for any unexpected factors that may drive it off course.

Technology development in Phase II included the design, integration and demonstration of aero-actuation controls, power sources, optical guidance systems, and sensors. The program concluded with a system-level live-fire test.

In 2009, the project was described as follows [.pdf]:

Extreme Accuracy Tasked Ordnance (EXACTO)* *Formerly Laser Guided Bullet.

(U) The Extreme Accuracy Tasked Ordnance (EXACTO) program is developing a system that provides sniper teams with the ability to identify and engage targets with heretofore unobtainable range and accuracy against stationary and moving targets under difficult environmental conditions, either day or night. The system uses a combination of a maneuverable bullet and a real-time guidance system to track the target and deliver the projectile to target. Technology development includes the design and integration of aero-actuation controls, power sources, and sensors. The components must fit into the limited volume (2cm to the third power) of a 50-caliber projectile and be designed to withstand a high acceleration environment. When integrated and tested, this system will greatly increase the effectiveness of two-man sniper teams, regardless of the environmental conditions and the time of day. The EXACTO technology is planned for transition to the Army by FY 2012.

FY 2009 Plans:

– Design guidance system.
– Design maneuverable projectile.
– Construct all novel 1x scale components.
– Measure component and subsystem performance in appropriate environments.

An Air University paper said this of EXACTO, comparing it to aviation precision guided munitions programs:

Foot soldiers are often left out of consideration when money is spent on precision weapons. The DARPA Extreme Accuracy Tasked Ordnance (EXACTO) is a command-guided .50 Cal sniper round designed to put long range, pinpoint precision in the hands of a common soldier. The system works by tracking a target with an infrared spotter’s scope that doubles as a command- guidance tracker. The .50 Cal bullet is fired and responds to trajectory commands sent by the scope (which tracks the target and bullet). The system accounts for wind, moving targets, and provides accuracy at range that normally requires years of sniper training to achieve. The EXACTO program not only gives sniper capabilities to common foot soldiers, it ensures a kill on the first shot, and enables moving target capabilities that have until now only been available to tactical aircraft and UAVs. In this case, the range is far shorter than HTV-21 or T32, but the strategic implications of super-sniper-battalions may prove even more deterring to an enemy force. For years, the real practical advantage US soldiers held over adversary soldiers came in the form of the air power watching over. EXACTO aims to enable America’s soldiers to enjoy technological advantages its airmen have enjoyed for decades.3

Although EXACTO was indeed scheduled to conclude in 2012 [.pdf], and some DARPA pages refer to it in the past tense, but the live fire test video shown here was shot in 2015 and only released in April (in-house, 10 Apr 15, to the public, 27 Apr 15).


  1. HTV-2: Hypersonic Test Vehicle-2.
  2. T3: Triple Target Terminator-3, an experimental missile that combined a ramjet sustainer with a rocket booster in the form factor of a pre-existing missile.
  3. Nielsen, Michael B. (Maj., USAF). Addressing Future Technology Challenges through Innovation and Investment . March, 2012: Air University, Maxwell AFB, Alabama.

Ghost Gunner is Shipping

Cody Wilson sent an update to Ghost Gunner buyers, along with this atmospheric video:

The Defense Distributed email says:

Today [24 April] the first wave of orders has finally shipped for our pre-order campaign that began all the way back in October! It’s difficult to even count the obstacles we’ve faced since almost that very month, but by your patience and support we are today able to announce our product’s shipment and the release of its design files and operation software to the public. We thank you immensely.

Over 100 units are shipping/will have shipped since the end of last week. Our output is at such a pace that we estimate current backorders from the original campaign will all be fulfilled within six to ten weeks’ time. Our manufacturing processes were difficult to engineer and perfect since December because of our troubled part stream, but we now realize our capacity and are doubling our work force to increase throughput even more than in the past two weeks.

They’ve also opened up orders for the first 200 of those on the wait list, as opposed to those who already paid and are in the queue (wait list members paid a small sum for a place on the list).

The biggest news, perhaps, is the release of the design files, software and manual.  These files are contained in a .zip that can be downloaded from here or here. (Note: this does not work with the Safari browser; Safari users will need a Plan B). The manual looks like this:


It is 30 pages long, although you only need the first six of them if all you plan to do is run .DD files created by others. The rest of the manual is an intro to creating .DD files and otherwise using Grbl to control the machine.

And we strongly urge you to read it now if you have a GG coming. It contains several things you’ll want to know before unboxing, like system requirements (in this initial version, “it’s complicated”), and what not to use as a handhold when pulling the machine from its box (the stepper motors!).

The machine’s planned cross-platform promise is not delivered yet, with the initial version of DDCut software, the automated software that runs a .DD file off on the router, initially live only on Windows 7 (and, if you’re brain-dead or your computer is, Windows 8). They still plan to make this work on Linux and MacOS, but it’s not there yet.

Users of the unix-like systems are not completely out in the cold, however. You can run g-code on these computers, controlling the mill by using GRBL. There’s much more of a learning code than that.

One of the problems with relying on someone else to write your DD file is that g-code is extremely powerful. A miscreant, then, could, if not exactly brick a Ghost Gunner, at least cause a head or spindle crash — not a good thing. Fortunately, Wilson and his merry men have included a short set of instructions about what g-code commands are usually safe and which are potentially hazardous, allowing any user to evaluate a .DD file’s safety. For better security yet, they suggest using only files from trusted sources.

We’ve been following this for a while (and yes, we have one on order, but we’re well down the list). We see real potential in g-code and .DD files.

UPDATE 0930R 20150425

This post was written rather rapidly last night when we came in from a long drive at 2300 with no 0600 post in the queue, so we have a few more points (both ours, and Cody’s) to get across to you.

How are the machines shipping? The answer seems to be, via US Mail.

When we say we see real potential in g-code and .DD files, here are some of the things we could see people developing and sharing:

  • Profiling files, for converting an M16A2-profile lower to an A1 profile for a vintage/retro repro.
  • Engraving files, to duplicate retro markings or to make custom designs.
  • Lightening files, to remove metal and skeletonize a lower (which, we must stress, saves no significant weight; it’s a style thing. Imagine a steampunk AR… now it can be done, and the design shared).
  • Things we can’t even imagine yet. If that doesn’t make you squee, what will?

Wilson sees that, too, maybe clearer than we do. Re the closed forum for owners only, he says:

As you receive your machine in the mail, you will find in your package a card with credentials to give you access to the Ghost Gunner forums. We expect this will be a place of exchange and development that will quickly travel more adventurously afield of DD to see just the range and extent of Ghost Gunner’s capabilities.

We note that Ghost Gunner does not require internet access to run, unlike some other modern manufacturing technologies. (MarkForged, we’re lookin’ at you, although we’ve been told they will be selling an extension to their software that will let MarkOne buyers opt out of the MarkForged cloud and run their own servers, in that pungent Silicon Valleyism, “Real Soon Now”). Yes, there is a forum for  Ghost Gunner users, but you don’t ever need to go there. You bought the machine, you own it. What you do with it is your business. (We suspect Wilson shares our loathing for hardware and software involuntary “licenses”).

[F]orum membership is not a must! Everything you need to operate the machine comes in the box, software and guide included. No need to connect to the internet to access what you’ve purchased.

And, in a very important and (to us) unanticapated update, the Ghost Gunner will now be offered Internationally, outside the USA as well. Release of the software was held up for months because:

[T]he Feds literally took until last week to give GG a commodity classification.

It’s anyone’s guess where the hold-up was. It could have been Fed animus towards Wilson personally, but Occam’s Razor suggests that it’s just Feds moving at their usual snail’s pace. But an aside of the classification and approval is this:

[W]e will begin selling and shipping Ghost Gunner outside of the United States. Many of you are not from the US and have inquired for months about access to the machine. Well, we now have the clearance to ship to over 30 countries, of which you are likely a citizen. Our international backers will be reached out to individually at this time, but you will note a separate path to get on the wait list if you’re outside the US when you now visit

Finally, it seems meet to close with Cody’s own elegiac closing, expressing as it does gratitude to those of us who have waited through all the Ghost Gunner drama.

Above all else, THANK YOU for your support. We’re a small shop of friends and relative kids from Texas (and parts) around who had no business opening a manufacturing operation. But we wanted to see this concept succeed, and we wanted it to succeed on bold and defiant terms.

Though it will still be some weeks before we’re caught up with orders, we know it was you, our backers, with your patience and good will that allowed us to get to this moment.

I for one will not forget it.

It’s unclear from the email when ours will ship. It looks like the first hundred is well in hand, but we’re just barely into the third hundred.

Jets (and Vehicles) with Frickin’ Lasers on They Heads

Doctor Evil’s technological dreams, not to mention Auric Goldfinger’s and Ernst Stavro Blofeld’s, are inching closer to reality. That’s the only possible conclusion an avid movie-goer will draw from a fascinating Bill Sweetman article in Aviation Week. 

Today, on an armored vehicle as an air defense weapon that doesn't need to "lead" a target; tomorrow, an aerial precision-strike capability? (Bill Sweetman AWST photo).

Today, on an armored vehicle as an air defense weapon with a functional MV of infinity, so it doesn’t need to “lead” a target; tomorrow, an aerial precision-strike capability? (Bill Sweetman AWST photo).

In fact, Sweetman deploys a bunch of pungent prose that sounds like something out of The Strategy Page, but with the essential difference that Sweetman knows what he’s talking about and has been wired into defense RDT&E since the second coming of laser weaponry (and the first serious, non-Bond-villain one) in the 1980s. Sweetman starts with a dismissive swipe at US and USSR laser weapons programs of the 1980s (“The only thing of consequence that any of them destroyed was confidence in laser weapons”), and then leaps into “that was then, this is now”-ville.

New HEL [High-Energy Laser] weapons are smaller than the 1980s monsters, with a goal of 100-150 kw, and powered by electricity rather than rocket-like chemical systems. Modest power permits more precise optics and—in some cases—the use of commercial off-the-shelf fiber-laser sources, improving beam quality (that is, focus) and reducing cost.

Star Wars lasers were intended to hit things that missiles could not touch. The new generation exploits different characteristics: a magazine as deep and easily replenished as the fuel tank, and a low cost per shot (about $1, says Rheinmetall). The idea is to deal with targets that missiles cannot engage affordably.

A mini-UAV is a threat because it can target ground forces for artillery. It is cheaper than any surface-to-air missile, but a laser can blind it, destroy its payload or shoot it down. Rocket and mortar defense is another application. Rafael’s Iron Beam laser is a logical follow-on to Iron Dome, which is practical and affordable only because it ignores rockets that will fall on open ground; that will no longer work when weapons are guided.

Hmmm. Thinking about the implications of what Sweetman is saying here, there are several paths around Iron Dome which the Palestinian terrorists may choose to adopt: they could try overwhelming it with quality, overwhelming it with accuracy (by guidance, as he suggests, or simply by increased ballistic accuracy and precision of aim), or overwhelming it with speed by using gun artillery instead of relatively-slow rockets.

Wile-E-Coyote-Genius-Business-CardNo doubt the cagey Israelis (has any nation’s paranoia ever been more justified?) have already thought this through and have counter-countermeasures in development (one of which certainly is a laser system). The Palestinians, in their ongoing attempts to outsmart the smarter Israelis, are the Wile E. Coyote of weapons development.

Anyway, let’s return to Sweetman’s rundown of current and very-near-future directed energy weaponry.

Close behind the systems already shown by Rheinmetall, Rafael and MBDA—certainly not a technological leap away—is the new Gen 3 HEL being developed by General Atomics Aeronautical Systems to fit on an Avenger unmanned air vehicle (AW&ST Feb. 16-March 1, p. 30). If what we hear is correct, it combines an output as high as 300 kw with high beam quality; it can fire 10 times between 3-min. recharges; and a version might fit in the 3,400-lb. pod that Boeing designed for the Advanced Super Hornet (see photo). A bomber or a special-operations C-130 could carry it easily.

This is a tipping point, because what you can do with 300 kw also depends on what you are trying to protect. If the goal is to knock down a supersonic antiship cruise missile (ASCM), there are two problems: water in the atmosphere (which attenuates laser energy) and the fact that a damaged ASCM can still hit the target. But if the target is an evasively maneuvering aircraft, it will often be in clear, dry air; and it is enough to destroy the missile’s seeker, put a hole in the radome, even at well-sub-kilometer range or weaken the motor tube to cause a miss, even at well-sub-kilometer range.

This is one where you’ll find it rewarding, we think, to open the mind and  Read The Whole Thing™. Sweetman is no more infallible than any of us, but he is a more informed aerospace analyst than almost any of us, and bears close watching.