Category Archives: Weapons Technology

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 Amazom.com (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).

Notes

  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:

gg_op_manual_cover

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 http://ghostgunner.net.

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.

Why This Guy is NOT Bubba

Here is a Glock pistol with a home-made modification: golf-ball like grip dimples. Whether you like it or not, it’s a personalization the owner is happy with, not that that alone prevents a hack job from getting the dreaded Bubba the Gunsmite label. (After all, some owners have extremely low thresholds of satisfaction).

Bubbas Glock

Nope, several things prevent this home-gunsmithing job from being the work of Bubba:

  • Not-Bubba did it with great care;
  • Not-Bubba made a plan first;
  • Not-Bubba followed his plan;
  • Not-Bubba took precautions to prevent damage to his Glock;
  • Not-Bubba practiced on other materials before taking his tools to the Glock, and even then,
  • Not-Bubba started on the least visible and most easily replaced bits of the pistol (in the case of a Glock G4, the replaceable backstraps).

Bubbas Glock 4

He tells his own tale on Reddit (with the ironic title: Burnt Plastic: How I Lowered the Value of my Glock, and the images of his work (with captions) are at Imgur.

Let’s let him tell a little of the story himself, beginning with why dimple your Austrian self-defense appliance:

I hate the grip texture on my G19. I have always shot Glocks well, but they feel like I’m holding a greased up pineapple. I’ve tried the grip tape. It greatly improved my grip for followup shots, but also had a tendency to peal off too easily and was too rough on my skin for carry also making my shirt ride up.
So I decided to take the plunge into grip stippling. Here’s the result. No, I’m not reselling it; no, I don’t care how it looks; Yes, I voided the warranty, and Yes, it feels MUCH better, both shooting and carrying against my back (8 o’clock, lefty).

This is a classic of home gunsmithing, actually, because Not Bubba took a generic, mass-produced pistol and made it better for him. Yes, it may punish him at resales time, but what’s the wholesale on a G19? They’re one of the least expensive firearms in class, new (especially if you get the LE discount, which we don’t know if he did). Nobody buys it for the resale value.

Remember how we said he practiced? He needed some Glocklike polymer to practice on and figure out what he was doing, and you may not have thought about it, but you probably have something pretty close, in your mag pouch.

Step 0: Practice and experiment. I bought a soldering iron with a bunch of tips. Some pointy, some round and skinny, some round and fat, some flat, etc. I used several of them to make different patterns on Pmags I had sitting around. Once I had a pattern I liked, I practiced on one of the back straps that came with my glock. Only after I was comfortable with the texture and pattern was I ready to work on the real thing.

That kind of incrementalism and thinking-it-through is evident throughout his activities. He drew out a plan for his dimples, once he figured out what size and texture he wanted, after sanding off the Glock factory sort-of-rounded-rectangles.

Bubbas Glock in-prog 2

 

The blue tape, put on before the sanding, keeps dust and grit out of the innards of the polymer frame. Note also that he steered clear of defacing any of the factory markings, which is a Federal (and most States, too) no-no .

A weird side-product of the dimpling process was a quantity of raised rings where the soldering iron had displaced plastic. The tool he used to shave them off is the razor-blade holder at left in the picture below. Bubbas Glock in-progress

 

Since he was hacking on the pistol anyway, he also relieved the rear end of the trigger guard to better suit his grip.

Bubbas Glock 2

End product: a customized Glock 19 that he likes better, can grip better and feels more confident about. And, not incidentally, the warm glow of having done it himself, rather than sending it out to a Glocksmith for the work. Note the regular rows of dimples, thanks to that sketched-on plan, as opposed to the random scattering that is the Mark of Bubba.

Bubbas Glock 3

 

Golf-ball dimples may not be your preferred surface treatment. In that case, don’t you do this to your gun. For this guy, it worked; it doesn’t look especially bad, and it’s not as if a Glock’s industrial design is gunning for a place in the permanent collections of the Museum of Modern Art anyway.

You can get the whole story, as mentioned above, on Reddit (complete with very thorough descriptions of tools used, down to the grit of sandpaper) and the images at Imgur (linked in the Reddit comment).

When Reverse Engineering goes to War, it’s “Technical Intelligence.”

Aviation Week is celebrating its 100th Anniversary over the next couple of years, and reprinting or blogging classic articles from prior years, and even from its various predecessor publications. This week they hit upon one that examines, and in part, reverse engineers, an ingenious weapons system we have mentioned before: the Japanese Type Zero Carrier Fighter.

zeke_32_hap_sideview

Aviation expert Bill Sweetman sets the stage with a long and informative blog post, and then the 1945 article is broken into four .pdf files. Sweetman:

Newsprint rationing clearly wasn’t a big issue in the U.S. in May 1945, when our predecessor title Aviation published an ultra-detailed four-part dissection of Japan’s “workhorse fighter”, the Mitsubishi A6M Zero, with detail that would put some homebuilt-airplane plans to shame. Neither was cultural sensitivity, as the cover wording shows.

The model examined here was the square-wingtipped, non-folding A6M2 Model 32 “Hap,” which had some tradeoffs designed to allow a more powerful engine. (It didn’t create enough speed to justify its extra weight, which shouldn’t surprise any aero engineers out there — aerodynamics are a much weightier influence on speed than horsepower).

zeke_32_hap_planview

The Zero was a design study in the combat multiplier of lightness in design, and is today a jewel worth studying and emulating by anyone who designs things and might like to make them lighter.

[T]he Navy’s requirement for speed and maneuverability comparable to emerging European designs… seemed impossible given the modest power of the biggest available engine.

What emerged was a highly refined design. Weight control was rigorous: Horikoshi wrote that “it was our policy to control anything heavier than 1/100,000th of the aircraft’s final weight”

Sweetman also notes one Zero advantage that we have mentioned before, the equivalent of 7075 Alloy, but he suggests that this wasn’t an oversight:

Aviation‘s story — quite possibly at the behest of the military — misses one key to the Zero’s success: its construction made use of high-zinc-content 7075 aluminum alloy, which had been secretly developed by Sumitomo and was significantly lighter than the 24S alloys used in the U.S. Better metals were not used worldwide until after the war.

Built-up rudder hinge bracket, where US engineers would have used a machined forging.

Built-up rudder hinge bracket, where US engineers would have used a machined forging.

US aircraft still use 2400 series alloys (as they’re numbered now, but they’re the same stuff) in skins and sheet structures, and 6061 in most things requiring plate, billet or cast parts. 7075 is used primarily in forgings. The clever Mitsubishi team under Jiro Horikoshi designed around the need for many forgings, substituting instead riveted assemblies of sheet aluminum alloy.

(Bill would probably be pleased, as he compares the sketches in the article favorably to homebuilt aircraft plans, to know that the rudder hinges and hinge brackets of our RV are built up from sheet and plate, much like some of the Zero’s brackets. So would Horikoshi, who passed away in the 1960s).

The full title and cutline of the original article is:

Design Analysis of the Zeke 32 Hamp: Presenting the 12th of our series, a profusely illustrated part-by-part examination of the Zero’s successor, showing how Jap engineers achieved unusually light structural weight without sacrificing strength.

All parts, .pdf

  1. Design Analysis of the Zeke 32, Part 1.pdf
  2. Design Analysis of the Zeke 32, Part 2.pdf
  3. Design Analysis of the Zeke 32, Part 3.pdf
  4. Design Analysis of the Zeke 32, Part 4.pdf

In addition to those four .pdfs, Sweetman’s post is definitely one where you’ll want to Read The Whole Thing™.

The scan has some issues, mostly at the edges and keeping the many figures straight and unwrinked, but it’s a great boon to everyone who studies How To Build Stuff.

And it’s a good look at a wartime case of digging into the enemy’s engineering.

 

HK’s Other 4.6: the HK36 in 4.6 x 36

HK LogoAround 1970, Heckler & Koch was doing well, but their restless engineers were thinking: what’s next? One thing we learn from history is that no weapons system lasts forever, and there was maybe one more go-around in the company’s present line of roller-locked weapons, trading some militaries’ 7.62 NATO weapons for 5.56 NATO ones. But what could offer stingy weapons procurers enough reason to stop sitting on their wallets?

HK 4.6 x 36mm, made 1971. For sale here. It seems likely that there was only one lot.

HK 4.6 x 36mm, made 1971. For sale here. It seems possible that there was only one lot each of the “soft core” (lead, this) and “hard core” (tungsten carbide) FMJ.

The company explored many ideas, in two major strains. One is now well-known: caseless ammunition with a radically new action and new modes of fire, which became the G11 through many, many series of tests and evaluations in the 1970s and 1980s. The second was, perhaps, meant as a technical backstop if the G11, a technical stretch, proved infeasible. It became the HK36 — not the G36, the technical backstop HK had to create after the G11 failed, but the very obscure G36. The rifle existed in, perhaps, three prototypes. It used a unique 4.6 x 36mm intermediate cartridge.

HK 36 factory photo, as published in Full Circle.

HK 36 factory photo, as published in Full Circle. This is the configuration we call Prototype 3.

The Big Ideas: Weight and Spoonery

When we referred to this as the “other” 4.6, we’re referring, of course, to the fact that this is not 4.6 x 30 HK round used in the familiar (at least, in appearance) MP7 series widely used by US and foreign special operations forces. The 4.6 x 30 is the latest of HK’s many attempts to make an even smaller caliber round, but it was aimed at a different objective: the short-range SOF and LE submachine gun, making most shots inside 100 meters; it has very light bullets (31-40 grains for warshots) and is a hair over half the weight of 9×19 or 5.56×25 ammo, allowing a reduction in operator burden (or an increase in ammo load, naturally).

The 4.6 x 36 was developed in the 1960s to meet a different requirement entirely: that of a normal assault rifle intermediate cartridge, with engagement ranges mostly inside 300 meters. Two ideas drove the 4.6 x 36: reducing ammunition and system weight for a given effect, arguably the longest-standing trend in firearms design, and increasing terminal effect in the intended target, to wit, enemy homo sapiens. The first objective drove the reduction in caliber and length. To get to acceptable lethality, higher chamber pressures (51,200 psi CUP) were accepted, but the light projectiles (42 grain hard core/54 grain softcore) didn’t reach outlandish velocities (2,600-2,800 fps). It required a fast barrel twist to stabilize the light projectiles; 1 turn in 6.3″ was selected. HK claimed the round shot flat, allowing it to print to point of aim from 0 to 300 meters without any need for range compensation by the shooter or the sight.

The “spoonery” of the subtitle refers to an invention of Dr Gunther Voss of CETME, which remained in symbiosis with HK itself at least at the time he applied for German and US patents in 1964 and 65 (his US Patent, 3,357,357, was granted in 1967).

Voss Loffelspitz US3357357-0

…to provide a rifle bullet wherein the tip of the bullet is of an asymmetric shape. When this bullet strikes the target, forces are generated which accelerate the bulet inclination.

It is stil another object of the present invention to provide a rifle bullet wherein the turning moment produced by the inclination accelerating forces increases and the bullet inclination is produced more rapidly when the distance between the bullet center of gravity and the bullet tip is greater. It is possible to increase the effect produced by the bullet tip asymmetry through the backward displacement of the bullet center of gravity.

The CG change could be produced by a dual-material cored bullet (later Russian rounds would take this approach, without using Voss’s tip).

Voss 4.6 x 36 Löffelspitz (l.) with 5.56 x 45 for comparison.

Voss 4.6 x 36 Löffelspitz (l.) with 5.56 x 45 for comparison.

Voss further believed that by increasing terminal velocity with the subtly asymmetric bullet tip he called the Löffelspitz or “spoon tip,” he could reduce caliber without losing lethality, and without having to “underspin” the bullet, which was widely understood to be Armalite’s approach to small caliber lethality.

In addition to the effective range increase, a bullet with these characteristics offers the advantage of the possibility of reducing its caliber without decreasing the detaining power obtained with the calibers used until now.

“Detaining power” is a euphemism used throughout the patent application. But clearly, the one biggest Big Idea in the HK36 was this ammunition.

The Three Known Prototypes or Versions

It is possible that some of these are actually the same rifle before and after rework. The fairly comprehensive (to its date) HK reference The Gray Room does not include a picture of an HK 36, suggesting that this may not have been preserved by the firm (or it may not be in display condition). Full Circle only includes handout publicity pictures.

The receiver of the rifle is very slender and short and, while surviving weight figures (6.3 lb empty) generated by marketing personnel based on prototypes are hard to reconcile with real in-service weights, it should have been much lighter than other HK rifles and more competitive with AR-15 based contemporaries.

Prototype 1 had a very conventional HK roller-lock styled receiver and magazine well, and very conventional HK (as far back as CETME) drum sight. It showed a relatively early plastic HK lower marked 0-1-30 and had an unusual sliding buttstock, clearly inspired by the Colt CAR-15, even though the HK36 did not require a buffer tube.

hk36 prototype 1

 

Prototype 2 also had a fixed magazine well, but the drum sight had been replaced by an, also Colt- or Armalite-inspired, carrying handle/sight mount. A reflex sight is contained within the after third of this sight, but we’ve never seen pictures of it, or of its reticle; we do note that apart from Prototype 1 (above), all HK 36 photos appear to be innocent of any foresight or any provision for iron sights. This image was featured in the 1975 Jane’s Infantry Weapons edited by FWA Hobart. Hobart reproduced a factory brochure for the rifle inside the book. He also, at the same time, featured this firearm in an article in National Defense, the magazine of the (then) American Defense Preparedness Association (which was earlier the Ordnance Association, and would later be the National Defense Industrial Association). By this time, possibly unknown to Hobart, the HK 36 was destined for the back burner as the caseless project was beginning to look feasible.

hk36 prototype 2

That picture doesn’t really do the sight-tower justice. It would be preserved in the next prototype and we’ll see it from some more angles.

Prototype 3 took another turn in the direction of space age looks with a fixed stock with a high center so that the recoil thrustline is barely offset from the stock centerline. This would have the  effect of reducing muzzle rise in high-rate fire, including auto- or burst-mode fire.

HK36b

The selector now has four positions: 0, 1, 25, and 3, for a three-shot burst. This appears to have been a burst at normal cyclic rate.

The unusual magwell appears also to be a little bit inspired by Armalite concepts: a disposable waffle-reinforced magazine insert made of aluminum.

hk36mag

Changing a magazine was a Heath Robinson task on the HK 36; it appears from surviving photos that you have to move the mag well latch to the rear which would let the spring-loaded side door open and then you could insert the 25-Round magazine insert into the well and press the side door closed. At this point you could resume fire.

It may have been even more complicated than that. This is how Major Hobart explained it in the National Defense article (via Full Circle, p. 346):

The magazine is charged as follows:

At the bottom of each side is a milled button attached to a spring-loaded chain carried inside the magazine. When the buttons are pulled down, the chain is extended and held out. This pulls down the magazine platform and compresses the magazine spring. The rear of the magazine is open, and the 30-round box is placed on top of the followers. A further pull on the chain releases the holding catch.

The magazine platform rises under the cartridges and passes inside the containing box. The chain is taken up into the magazine. The first round is now in position for loading, and when the bolt comes forward the top cartridge is fed into the chamber. The magazine is sealed against the entry of dirt, snow, etc. As subsequent rounds are fired, the magazine spring drives the follower farther up inside the ammunition box. When the last round is fired, the bolt is held open. When the chain is pulled down, the empty box is ejected, the magazine spring is fully compressed, and the platform is pulled down to allow the next ammunition pack to be inserted.

(This is what happens when you ask a room full of guys whose names terminate in Dipl. Ing. to simplify something). HK claimed that this would “reduce weight and cost.”

It’s unfair to judge the magazine system based only on images and descriptions, but the temptation to pass judgment is strong. In any event, it is not the only ergonomic question mark with these firearms. The usual HK selector switch seems to call for the usual double-jointed thumb, especially on the burst setting; also, a stock weld of any type looks practically impossible, whether you’re using the fixed or sliding stock versions. (In true HK roller-lock fashion, they’re easily interchangeable. HK was modular before modular was cool).

The close-up of Prototype 3 shows the unusual shape of the forward carrying-handle pillars, and the only reason we can think that they’re bowed out like that is to keep them out of the field of view of the mysterious reflex sight. At around this time, HK was working with Hensoldt on a reflex sight for the G11; this might be the same sight.

Note that these “Prototype numbers” are not anything assigned by HK, but something that gun watchers have applied to these photos over the years as they’ve surfaced. We’re not aware of any picture showing more than one HK 36 in any one place at any one time, so it’s quite possible that there was only one prototype, and it went through several different reconstructions. It’s also possible that at least some of the weapons in the factory photos are actually mockups or dummies, and were never built as working firearms. The existence of quantities of the 4.6 X 36 ammunition argues for the existence of functioning prototypes.

What Happened to the HK36?

We know, in broad terms, what happened with the project. As the 70s wore on and the G11 project for a 4.9 mm (later 4.7 x 21) caseless Wundergewehr came together technically, the HK 36 and its unique 4.6 x 36 mm round vanished back into the swamps of, if not Mordor, at least Oberndorf. The G11 project was all-consuming, and it was this close to Bundeswehr adoption and standardization, having demonstrated a 100% pH improvement over the G3 rifle, when it was overcome by events. The Berlin Wall crumbled, and Germany entered the phase of Wiedervereinigung — the reunification of a nation divided in twain for almost 50 years. With the defense demands that resulted from this unexpected boon, including the challenges of merging two completely incompatible sets of armed services, it would have been irresponsible to sink great resources into rifle re-armament — so they kicked that can down the road, and stuck with the obsolescent G3.

The G11, which had already been rejected by the US Army when it cancelled the Advanced Combat Rifle procurement program in 1990, went into the lockers, too, and HK was briefly without a future in the infantry rifle market (right when worldwide Police/SOF enthusiasm for its submachine guns was running out of steam).

When HK found its future again, it wouldn’t be roller-locked or caseless. So one of the salient facts about the HK 36 is that it was, indeed, the last of a long line that began with the Mauser Werke StG 45. For that, as well as its innovative ammunition and concept, it deserves to be remembered.

We are aware that this post is far from comprehensive, but we think it tells the story of this rare experiment to the extent that it’s been made public. If there is a single thorough article on the HK 36 in the Intertubes somewhere, we did not find it. The best and most authoritative sources, based on factory information, are those 1975 Jane’s and National Defense articles, and three short pages in Full Circle, which reproduces much of the ND article’s content. 

Firearms Reverse Engineering

One thing about the people of the gun: we’re conservative. By that, we don’t necessarily mean that we want 15 carrier groups back, eager to cut taxes and services, or sorry that mandatory chapel was gone by the time we went to college. There are actually card-carrying ACLU members and ivory tower socialists among us, but they’re conservative about their guns. For every reader who’s up to date on polymer wonder pistols, there’s about three who wish you could get a new Python. (The reason they can’t is that they don’t want it $3,500-4,000 bad, which is what an old-style hand-made perfect Python would cost to make today). Or a new Luger. For every one of you guys following the latest in M4 attachments (hey, let’s play “combat Legos!”), there’s a few who’d buy a new MP.44, if they could.

Every once in a while, gun manufacturers decide to satisfy these consumer yearnings with product. Sometimes, they succeed. Sometimes, the 10,000 guys who told them they were down for a semi-auto Chauchat turn into 10 guys who buy one and the businessmen get to undergo the intensive learning lab called Chapter 7 bankruptcy. The question becomes, if you are raising a zombie firearm from the dead: how? Even the original manufacturers tend not to have prints and process sheets for >50 year old products, and if they do, the documents are ill-adapted to the way we do things now. If your original product was made in Hiroshima or Dresden pre-1945, or Atlanta pre-1865, odds are the paperwork burned. If the company went tango uniform even ten years ago, rotsa ruck tracking down the design documents.

So, you’re sitting here with a firearm you know you could sell. You have the rights to reproduce it, because any patents and copyrights and trademarks are either in your possession or expired or defunct. Your problem is reverse engineering. It turns out that this is a very common problem in the firearms industry, and the path is well beaten before you.

Some Examples of Reverse-Engineered Drawings

People can do this with some calipers, a dial indicator, and some patience. Rio Benson has done that for the M1911A1.

Screenshot 2015-04-03 09.58.55

He explains why he thought a new set of documents were necessary in a preface to his document package:

Historically, when the drawings for John M. Browning’s Colt M1911 were first created, there was little in the way of ‘consensus’ standards to guide the designers and manufacturers of the day in either drawing format or in DOD documentation of materials and finishes. For the most part, these were added, hit or miss, in later drawing revisions. Furthermore, due to the original design’s flawless practicality and it’s amazing longevity, the government’s involvement, and the fact that in the ensuing 100-plus years of production the M1911 design has been officially fabricated by several different manufacturers, the drawings have gone through many, many revisions and redraws in order to accommodate all these various interests. These ‘mandated by committee’ redraws and revisions were not always made by the most competent of designers, and strict document control was virtually non-existent at the time. All of this has led to an exceedingly sad state of credibility, legibility, and even the availability of legitimate M1911 drawings today.

He modeled the firearm using SolidWorks 2009, with reference to DOD drawings available on the net, and his own decades of design and drafting-for-manufacture experience. The results are available here in a remarkable spirit of generosity; and if you want his solid models or his help producing this (or, perhaps, on another firearm), he’s available to help, for a fee.

findlay-stenIn a similar spirit, experienced industry engineer David S. Findlay whom we’ve mentioned from time to time, has published two books that amount to the set of documents reverse-engineered  from an M1A1 Thompson SMG and from a Sten Mk II. The limitations of these include that they come from reverse-engineering single examples of the firearm in question, and the tolerances are based, naturally, on Findlay’s experience and knowledge. So his reverse-engineering job may not gibe with the original drawings, but you could build a firearm from his drawings and we reckon the parts would interchange with the original, if his example was well representative of the class.

Nicolaus M1 Garand bookOn the other hand, Eric A. Nicolaus has published several books of cleaned-up original drawings of the M1 Garand, the M1D, the M1 and M1A1 carbines, various telescopes, etc.

Nicolaus’s books provide prints like the Findlay books do, but they’re not reverse engineering. They’re reprints of the initial engineering, cleaned up and republished. Not that there’s anything wrong with that.

Sometimes the Industry needs Reverse Engineering

A perfect example is when planning to reintroduce an obsolete product. Most manufacturers that have been around since the 19th Century never foresaw the rise of cowboy action shooting, but now that it’s here, they want to put their iconic 1880s products in the hands of eager buyers. Or perhaps, they need to move a foreign product to the US (or vice versa). In this case, reverse engineering the product may be less fraught with risk than converting paper drawings which use obsolete drawing standards, measures and tolerancing assumptions. You may recognize this reverse-engineered frame:

reverse-engineered_walther_frame

If you are exploring a reverse engineering job, there are several ways to do it. The first is in-house with your own engineers. (You may need to ride herd on them to keep their natural engineers’ tendency to improve every design endlessly in check). The next, is to outsource to an engineering consultancy that does this. The third is to use a metrology and engineering company, like Q Plus Labs, from whom we draw that pistol-frame example. They say:

[W]e offer numerous reverse engineering methods and services to define parts or product. Q-PLUS provides everything from raw measurement data to parametric engineering drawings that correspond to a 3D CAD solid model! We also offer reverse engineering design consulting to point you in the right direction.

  • Digitizing & Scanning
  • Measurement Services
  • 3D CAD Solid Modeling
  • Engineering Drawings

In other words, you can go there to have them do, essentially, what Rio Benson did with the 1911 with your product. They can digitize an item from 3D scanning, or they can take a drawing and dimension it from known-good examples. Given enough good examples, they can actually determine tolerances statistically and substantiate them to a level that will satisfy regulatory agencies such as the FAA. (This lack of a range of parts and statistical basis for the tolerances is, in our opinion, a rare weakness in Findlay’s single-example approach).

Reverse engineering has gone from something in the back alleys of engineering or attributed to overseas copycats, to something firmly in the mainstream of modern production engineering.

Printed 10/22: Several Ways to Make Your Own Rimfire

In the world of rimfire rifles, the Ruger 10/22 lives in the equivalent mindspace of the AR-15 in Centerfire World: it’s the center of an entire ecosphere of modular customization. You can buy any component for a 1022 that you might like, except the receiver. Wait! Belay that: there are also aftermarket receivers1 and even “80%” receivers2. And then, there’s 3D printing.

A printed Ruger 10/22-based pistol.

A printed Ruger 10/22-based pistol.

There are several ways to 3DP a 10/22 receiver that’s a fair ringer for the pukka article.

Printed 10-22 with original 9 Mar 15

For years a drawing and 3D model [IGES] of the receiver has been available online. (We downloaded it years ago from CNC Guns, where Justin Halford may have intended to mill it from billet). It was only natural that people would think of duplicating it on a 3D printer in PLA or ABS. And it’s definitely been done. Voilá:

https://www.youtube.com/watch?v=kTv6xgaSghY

Indeed, 3D printed guns pioneer Have Blue posted about success printing a 10/22 receiver over two years ago. He may have been overlooked because it was an aside to his experiments with AR lower receivers. Here’s what it looked like on the printer:

10-22 as printed

And here’s what one looks like with the support material removed. This one was printed on Veterans’ Day, 2013 (Remembrance Day for our British and Commonwealth cousins):

This printed receiver image has been in our media library since February.

This printed receiver image has been in our media library since February, but it was already a year old then.

But there have been a bunch of new stories in 2015 addressing this3, and we have seen that a couple of the original gun-printers from way back have taken to the net again to point out their primacy, from 2013, and helpfully to organize it into a simple step-by-step process (but one, as you will see, that needs considerable machining tools and knowledge to correct for issues with the IGES file or the print). Most if not all of that detail was in Have Blue’s original post from St Patrick’s Day, 2013. But here’s the new iteration of that, from a new-ish site, Printed Firearm.

 

In comments to his post, Have Blue noted that

My hunch is that accuracy/precision will be pretty much the same with the printed receiver when using the factory iron sights (as both are mounted to the barrel itself). However, if using a receiver mounted scope or aftermarket rear iron sight, I expect to see very poor accuracy – given that the barrel would tip down with every turn of the clamp screws during the initial barrel mount, it’s not conducive to accuracy. The printed receiver is far more flexible than an an aluminum receiver, and is really quite impractical at this point (I wouldn’t want to do mag dumps in the summer due to heat concerns, to answer your other question).

But that’s where we were in 2013… “What is the use of a newborn baby?” as Franklin is said to have replied, when asked, what was the use of the Montgolfier Brothers’ balloon.

Since 2013’s initial reconnaissances of the 3D-printing world, we’ve seen printing evolve with new materials, vastly improved printers, and other individuals have solved some of the 10/22 printing problems Have Blue had to machine his way out of, by modifying the 3D file and printing the corrections (and adjustments for shrinkage, etc.) into the receiver. For example, the receiver can be printed in sections, oriented for accuracy and strength, and then epoxied together.

Here’s a pistol “Ruger Charger” version which was done just that way (in fact, the image is from this video) from 2014.

http://www.liveleak.com/view?i=b3e_1404502736

This is one cat that is just not susceptible to being rebagged. The authorities can’t issue the crackdown they’re dreaming of, without cracking down on a great deal of unrelated economic and technical growth and development.

GSL printed 10-22

Some European authorities have chosen to extend bans to other parts, perceiving that the manufacture of, say, bolts and especially barrels is beyond new technology or cottage industry in general. (They are very mistaken about this).

Pretty amazing stuff, but then, this is the twenty-first century.

Notes

  1. An incomplete list of 10/22 aftermarket receiver makers includes: KIDD (link is to a reseller), MOA Guns (review of their stainless 10/22 receiver), NoDak Spud, Tactical Machining (here’s a review), and Volquartsen Custom, each with some selling points or improvements built in.
  2. Makers include Select Fire LLC and Tactical Machining (uses this completion jig). Scare quotes because, while “80%” has some currency in gunners’ discussions, it means zilch to ATF Firearms Technology Branch. In their (legally binding) opinion, something is a receiver — and therefore a firearm — or it isn’t, and percentages don’t enter into it at all.
  3. The one that caught our eye was this one at Guns Save Lives.

Wednesday Weapons Website of the Week: Just Fieldstrip

Just Fieldstrip is not exactly a website, but it’s a series of YouTube videos posted via check gun expert. As the name suggests, almost all of them are simply how to field strip quite a collection of historic, and sometimes rare and unusual, firearms.

The only audio is instrumental music, so they’re useful to speakers of any and no language alike. There’s a playlist of the series, but it hasn’t been updated in two plus years, and stops at #75. (We’ve found examples up to #90) There’s also a playlist of the series with no music and running narration — in Czech. Great if you have the right credentials (say, Defense Language Institute Basic Czech 1979-80, FLTCE Immersion Czech 1986) but maybe not so great if you don’t.

Here’s one that isn’t actually a field strip, simply an example of how to operate the Kolibri 2.7mm automatic pistol, which looks like a Baby Browning’s premature crack baby with the Browning 1900 fingered as Baby Daddy. (Was incest illegal in Liège early last century? Enquiring minds, etc. –Ed).

The Kolibri is Number 054 in the long-running series.

One of the more fiddly and complicated disassemblies is the fiddly and complicated Luigi Franchi SPAS-12, a bizarre shotgun that worked as a semi-auto and as a pump.

After the jump there’s a list of some, perhaps all to date, of the videos. Some we could only find in the Czech variant, some in the dubbed-music variant. Going through that list, we found one from a pistol we didn’t know, the Slovakian polymer-framed DA/SA Grand Power K-100, reported to be winning IPSC events in Europe. So we’ll close the front page out with a third video, the K-100 — Just Fieldstrip! (Interesting, the barrel rotates to look like an Obregon or some Berettas, but it strips like a PPK. We’ll have to look into this thing).

The author of these videos is associated in some manner with a Czech gun dealer, GunDrak.cz. The page is naturally in Czech. It has a video page that links to the Czech disassembly videos, too.

Click “more” to see the list of Just Fieldstrip / Rozborka a Sborka episodes we could find. (Unfortunately, not linked).

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