Category Archives: Weapons Technology

3D Printing Update

Recently, we attended a local 3D printing seminar put on by Alpha Imaging, the New England/Northeast representation for giant vendor 3D Systems. It was very enlightening, and we came away with a lot of ideas for 3D printing, scanning, and software that apply both to our firearms activities and also to our more general defense and aerospace consulting efforts.

We had to give a pass to a much bigger multivendor expo in New York City this month; the dates conflicted with a major Florida airshow. Fortunately, Reason Magazine attended and had a video and web report on the show. Video first:

Some text from the same Reason page:

3D printing has the ability to revolutionize the way we make practically everything, from guns to pastries and everything in between. Reason TV recently had the opportunity to attend Inside 3D Printing Conference and Expo, a 3-day event held in New York City.

There they met up with trailblazers in the 3D industry who were able to give them the inside-scoop on how 3D printing will revolutionize the economy.

via 3D Printing Will Change Everything – Hit & Run : Reason.com.

The ChefJet is one of the products that was teased by the Alpha Imaging guys. 3D Systems will be introducing that this year, and so they have a range of systems that print everything from food to hard plastic or steel end products (these are the top of the line SLS and DMLS systems) to gypsum-based architectural models (heavy! But they can do overhangs beautifully), to tooling in everything from wax (for casting patterns) to plastic (can be injection molds or even hydroforming molds).

One of the most interesting displays was of 3D scanning and reverse engineering technology. And yes, we’re going to put that to the test Real Soon Now.

Why Count Rounds?

The Army's experimenting with automated round-counting systems.

The Army’s experimenting with automated round-counting systems in the interests of better maintenance.

Well, back in SOT, the chief pistol instructor, the late Paul Poole, used to tell us “Never dry fire in a firefight!” In those days, CT work (only the British called it CQB then) was done with pistols, although we were experimenting with both the newfangled H&K MP5 and Colt’s oldfangled XM177s, a few of which were around but very beaten-up; Colt had a new version with a 14.5″ barrel that they said solved all the 177′s problems, except for the big fireball and ear-shredding report. 

We’d have gone to Hell to bring back the three heads of Cerberus for Poole, a Son Tay raider and Bob Howard’s recon-running-teammate, but it wasn’t just for his history: the guy was a dead shot, making steel E silhouettes ring with a .45 at 100 yards, and entertaining as hell, with a foghorn laugh: “Bwah-hah-hah! Never dry fire in a firefight!” when one of us was caught with his figurative pants down and his literal 1911A1 slide locked back. And his instruction was pure common sense and experience, and we all got better — a lot better — under his tutelage. 

Even if he did assess our personal pistol skills and make a little presentation in front of the guys: an M79. “Hognose, you need an area fire weapon. Bwah-hah-hah!” Ouch.

Later we found out that it was simply that somebody had to be the team grenadiers, and two of us were pulled for the honor. Poole just couldn’t resist making fun of us. (On the plus side, you get creepily good on a 79 with a couple 72-round crates a day to burn. Even if it does chew up the web of your hand).

But we did start counting rounds, at least, per mag. With the 1911, of course, it was easy. It would go bang exactly 7 times from start, and if you forgot in the stress of action how many bangs you had left, you dropped the old mag in your leg pocket (if you had time) and started counting from 7 again. What we didn’t do, though, is count rounds total. Only the snipers did that, and that was because their M14-based M21 sniper systems were a bit of a hothouse flower, sacrificing some of the M14′s robust Garand-based strength for excellent accuracy.

The snipers! Those guys were firing over our heads and next to us as we went in on training targets… one we recall with clarity was a set of wooden stairs with a door at the top and windows to its sides. In the door were two concrete cinderblocks and in each window was another. The snipers had to (and did) pop the blocks in the door as we assaulters charged up the stairs, popping the blocks in the windows with our .45s. The life of the M21 barrels was not long (the snipers did not clean them vigorously, to prevent muzzle wear; the M14 design doesn’t allow cleaning from the breach).

None of the 1911A1s had been built, as far as we knew, after 1945, and God alone knew how many rounds they’d seen. The 1911 would keep firing until a Magnafluxing at one of the periodic rebuilds showed cracks, usually in the slide. The round counts on the 1960s-vintage M16s and XM177E2s were also a mystery. Or even the newer CAR-15 carbines or MP5s… they got shot a lot.

But the idea the snipers had, to count the rounds so you knew when the rifle was about ready to go back to depot, was a good one. They actually logged them in a book (and this continued when the more-accurate and -durable M24 replaced the somewhat improvised M21 with its Leatherwood Automatic Ranging Telescope). The trouble is, of course, that logging rounds is a great deal of work. But if the whole Army could do it, we’d get a lot more information about how long small arms and their components are good for, and we could begin to schedule inspections and overhauls more intelligently. Too many inspections waste money, and some percentage of overhauls go and rebuild guns that don’t need it, while some other percentage of guns that need overhaul, based on their condition, don’t get picked up. (Army ordnance experts think that both of these numbers, the false positives and the false negatives, are about 40%)

For over 10 years the US Department of Defense’s Joint Services Small Arms Program and its constituent service ordnance departments have been trying, with limited success, to develop an automatic round counter for combat firearms. SOF elements have moved ahead of the JSSAP on this, thanks less to general SOF awesomeness, and more to SOF budgets, and they’re futzing around with fielding round counters now.

While the civilian market has round counters, they remain fiddly and unreliable, and many of them are focused on counting down the rounds in your magazine. The military frets less about that, and more about the problem of wear and tear on high cycle small arms. What they’re looking for is something that will give them a shortcut to understanding the condition of a firearm. They see this working in the way that an odometer lets you judge the point a car is at, in its factory-to-scrapyard lifecycle.

There are several ways that systems subject to wear and tear can be singled out for overhaul or rebuild:

  1. They can be selected due to calendar years of age since production or last overhaul. This is what historically has been done with most Army small arms.
  2. They can be selected “on condition.” This means that they are subject to frequent inspections, and weapons that failing inspection criterion or criteria are selected for overhaul. This is the other mechanism that sends Army small arms to the depot for rebuild.
  3. Or, lastly, they can be selected based on usage metrics. This is not done currently, because apart from sniper weapons, and for that matter, sniper weapons used by SOF mostly, few weapons have their usage recorded accurately and reliably.

Each of these approaches has problems. Calendar year replacement means that most parts you are replacing will probably still have many years of service in them. Likewise, many of the problems that degrade small arms accuracy and reliability can’t adequately be documented in an armorer’s condition inspection. Finally, usage metrics also are imperfect: evidence teaches us that not only the amount but also the intensity of use has an effect on weapons wear.

Why Counting Rounds Works for Weapon Maintenance

Let’s consider some real-world examples. The things that kill Stoner system rifles are barrel wear (which degrades first accuracy, then reliability) and metal fatigue in the locking mechanism, especially in the bolt (which is primarily a reliability threat.

The two real problem areas in rifle barrel wear are throat erosion and gas port erosion, both of which degrade accuracy and reliability. But the means the Army currently uses to detect throat erosion, the same taper gauge used to detect muzzle erosion, doesn’t work reliably at the back end of the barrel. It misses a high percentage of badly eroded chambers (well, actually, throats), “false negatives,” while identifying a rather high percentage of “false positive” chambers, that are still perfectly accurate. And outside of the depot, where the port can be examined with a borescope, there’s no way to judge gas port erosion at all.

 

Note that two of the seven lugs had failed. After the first one lets go, the overloaded remainder fail in rapid succession.

Note that two of the seven lugs have failed. After the first one lets go, the overloaded remainder fail in rapid succession, unless the broken lugs jam the rifle..

Fatigue undermines the bolt all over, but the bolts fail in two areas: the locking lugs, and at the hole for the pivot pin. Both are places where the metal is limited but stresses concentrate.

A locking lug failure (like the single-locking-lug failure common on the Beretta) may not immediately fail the weapon. That depends on where the broken chunks of lug go; but most places they might go will interfere with something. Moreover, as each lug fails, the remaining ones bear more burden, and they usually fail in an accelerating sequence as the burden of seven lugs is borne by six, five, four… the gun generally jams before you get to zero.

The next most common place for bolt failure is at the thinnest section of the bolt, where it’s drilled through to accept the pivot pin. Any asymmetry in forces here, which may result from even microscopic as symmetry of the park part, causes the forces to load up on one side or the other, and over a great deal of time, or if there’s a presence of a Nick or any other stress riser, crack begins to propagate on one side or the other. Even before the first side is completely cracked through, it’s weakened ability to bear loads increases stress on the other side, Waiting to a matching crack over there. The bolt can crack through on one side or on both, and is cracked through on one side, will quickly crack through on the other. A redesign of this area to reduce the diameter of the pivot pin, leaving more cross-sectional material in the bolt, or adding rollers to reduce friction, might increase durability here. It’s hard to judge whether it’s actually necessary, because bolt failures are relatively uncommon, and redesigning the pivot pin mechanism may introduce new failure modes.

Usually a crack at this point occurs on one side first, and can be spotted with the naked eye.

Usually a crack at this point occurs on one side first, and can be spotted with the naked eye before it propagates across the entire bolt.

The bolt seems to fail, whichever failure mode gets them, before the lugs in the barrel extension let go. Obviously bolt failures are catastrophic failures that take the weapon out of service either instantly or very rapidly (within a few more rounds); there is no fail-safe bolt failure mode. Bolt failures always occur during firing, never during non-firing weapons-handling, and therefore they have a potential to happen during combat, which is by definition a Bad Thing.

The current maintenance schedule sends small arms to the depot for analysis in large batches, commits weapons to overhaul that have years of useful life, or, even worse, sends them after they display failure in the field. Everyone knows that you have to turn in the rifles with the broken bolts illustrated here. What we don’t know is: can you catch the problem before it is catastrophic, or even visible, with round-counting?

So this is the why of round-counting (there are a few other wear modes, like to the gascheck rings, but this is the meat of it). First, we can use round-counters to identify specific weapons that have had higher usage than their rackmates, and that we would expect, ceteris paribus, to be be more needful of maintenance. Once we have an automated round-counting system in place, we can correlate round-counts with wear and failures systematically, and the data-collection potential gets interesting. A first-generation round counter is itself certainly useful, but still a rough device. All rounds are not equal, and that leaves us growth potential for improved future versions. We know from decades of experience, for example, that automatic fire wears guns of all kinds more severely than the same number of rounds fired semiautomatically, and that heavy, sustained automatic fire is very deleterious to accuracy. You may recall this post from last year wherein we noted that WWII armorers observed that .50 ANM2 aerial machine guns that had been fired in long bursts lost their accuracy even though the barrels gaged normally in all dimensions. An M4A1 is not a .50 but there may be analogies in the physics and metallurgy at work in each.

Round counters give us data points we didn’t have before, in other words.

(When we figure out where we stowed it, we’ll link the 2006 SOFIC presentation from which the images and many of the facts have been drawn).

Wednesday Weapons Website of the Week – Torpedo of Rijeka

Robert Whitehead was a pacifist and teetotaler, who invented a weapon that's in its second century of use and development.

Robert Whitehead was a pacifist and teetotaler, who invented the naval torpedo and sold it all around the world: a weapon now well into its second century of use and development.

Here at Weaponsman, we’ve discussed naval torpedoes before. We’ve done it in the light of early American torpedoes that have been recovered from the bottom of the sea, or otherwise rediscovered, and displayed in museums or otherwise studied. But the very first torpedo, at least the first successful one, came from the forgotten Navy of the Habsburg Empire, by way of an English inventor and entrepreneur.

Fortunately, there is a place where this early history is not only not forgotten, but preserved and memorialized, and it is present on the web at Torpedo of Rijeka, our Wednesday Weapons Website of the Week this week. It’s a website founded by enthusiasts of the first naval torpedo, and the first naval torpedo factory — in their Adriatic hometown.

When Farragut said, “Damn the torpedoes,” in the Civil War, the “torpedoes” that he referred to were what we think of today as naval mines. They were tethered to the bottom or shore, and meant to inhibit naval traffic. While mine warfare is still a very important part of naval offense and defense today, the word torpedo has come to mean an underwater projectile or missile,  self-propelled with propellers or jets, and aimed at a particular target. Torpedoes can be fired along a pre-determined course or guided in some way. This guidance today can be on-board or remote, in the latter case usually wire-guided much like an antitank missile.

The inventor of the torpedo as we know it was Robert Whitehead, a Lancashire engineer who had long worked on the Continent. He was working in Trieste, then an Austro-Hungarian seaport, when he was essentially head-hunted by another firm, and moved down the coast to Fonderia Metalli de Fiume, in a port city which has had many names and flown many flags over the centuries since Roman historians noted that a tribe of rude Celts lived on the hills and a “more civilized” tribe of mariners lived in the seaport. The Romans called it Tarsatica.  By 1856, when Whitehead and his family arrived, the city was known as Fiume in Italian (which many of the inhabitants spoke, regardless of their loyalty to the Dual Monarchy), Fiume in Hungarian (technically, it was part of the Hungary half of the Empire), Sankt Veit am Pflaum in German (the lingua franca of central Europe in those days) and Rijeka to the local Croats, who had to learn one of the other languages — or better yet, all of them — to advance in society and commerce. As an empire, Austria-Hungary was a very different concept from the nations of today; one’s ethnicity was not implicated in his political allegiance to the extent it is in the post-Fourteen Points world.

Fiume was also the location of the Austro-Hungarian Naval Academy, which like any major power’s academy not only trained future naval officers but sponsored research. This included pioneering research in photography, communications, physics, and, more to our point, remote-controlled weapons. Whitehead’s company, now yclept Stabilimento Tecnico Fiumano (Technical Establishment of Fiume), at first made high-tech machinery of the era, such as steam engines for naval ships. They were tied in tightly to the Naval Academy and the local academic community; for example, technicians at what would become the Whitehead torpedo plant provided the first experimental proof of Mach’s concept of the influence of the speed of sound on aerodynamics.

A different kind of "Coast Guard," this primitive weapon inspired the naval torpedo we know today.

A different kind of “Coast Guard,” this primitive weapon inspired the naval torpedo we know today.

By happy coincidence an officer (Commander — Fregattenkapitän – Giovanni Luppis) was struggling with a remote-controlled surface boat IED he’d invented, which he called the Coast Guard. His surface torpedo — for that is what it was — had a spring-and-clockwork mechanism and steering bridles for control from the shore, and a contact fuze for detonating if someone was lucky enough to guide it onto an enemy ship. Here was a problematic gadget, but the germ of a very good idea, and Whitehead and a talented team including his son John and his right-hand man, Anibale Plöch. Unlike many Victorian Age inventors, Whitehead seldom sought patents, preferring to maintain his technical advantages as trade secrets.

And technical advantages he had.

Whitehead's (and the world's) first torpedo, 1866.

Whitehead’s (and the world’s) first torpedo, 1866.

 

To make his torpedo work, Whitehead and his team had to solve several problems: propulsion, stability&control, and effect. The last of these was the easiest: a cylindrical bronze torpedo could carry sufficient explosive to sink any modern dreadnought, and, moreover, deliver it below the water line where the ship was most vulnerable. The Empire was well-stocked with talented artillerists and engineers, and neither fuzes nor explosives required research, simply development. That part was basic engineering, not science.

The true developments were propulsive and control based. Whitehead used steam for the first torpedo, and then changed to a compressed-air-powered piston engine, for more power and quicker preparation to fire. The compressed-air engines were made in a variety of designs and layouts.

Of course, the engine is only half of a naval powerplant — the other half is the propeller.  These three recovered torpedo tails tell the story of improved propellers (they also show the growing awareness of fluid dynamics. The first torpedo was sharply spiked fore and aft — by the end of the 19th century, a blunter shape with a round nose was proven to generate less hydrodynamic drag).

1868 torpedo shows pointed end and single-screw with a duct ring.

1868 torpedo shows pointed end and single-screw with a duct ring.

1884 torpedo is a little thicker and has introduced dual counterrotating props to neutralize torque.

1884 torpedo is a little thicker and has introduced dual counterrotating props to neutralize torque. The ring was found to inhibit propeller efficiency.

1898 torpedo has a more organic shape and well-uptimized counterrotating screws.

1898 torpedo has a more organic shape and well-optimized counterrotating screws.

Devices pioneered here for control were a mechanical depth control and a variety of steering gyroscopes. John Whitehead tried to develop a torpedo gyroscope but his model was a dead end. Instead, they purchased a design from former Whitehead engineer Lodovico Obry. Much of this history is recounted on the Torpedo of Rijeka website.

The Obry gyroscope

The Obry gyroscope

In the years leading up to the Great War, Whitehead’s company, Torpedofabrik Whitehead AG, was controlled by a British syndicate of the arms and engineering giants Vickers and Armstrong-Whitworth, who’d acquired it on his death in 1905 and continued torpedo development.

After the breakup of the Austro-Hungarian empire at war’s end, the factory was acquired by an influential Italian family, and its name was changed to an Italian one, but cutting-edge torpedo development for all nations resumed. The testing station on the docks had a new level built with a catapult to simulate aerial torpedo launches.

The torpedo launch test station offered a ship-launch level, and air-launch level with catapult, and an observation level.

The torpedo launch test station offered a ship-launch level, and air-launch level with catapult, and an observation level.

The plant resumed torpedo production again after being bombed by the Allies in World War II, but ceased that production in the 1960s. The physical plant and its distinctive torpedo test tower (alas, not the original from 1866 but the upgrade from the 20th Century) still exist. The enthusiasts of the Torpedo of Rijeka website hope to establish a permanent museum to their city’s most enduring export. Rijeka today is a sun-blessed city on the Adriatic coast of Croatia, and a reasonable European vacation destination.

Whitehead had a most remarkable life. His daughter Alice married the skipper of the Austrian boat that tested and validated his prototype torpedoes; his granddaughter Agnes inherited his vast fortune, and she in turn married an Austro-Hungarian minor nobleman and naval officer that she met at a sub commissioning. The officer would later command that sub and another on his way to becoming the Empire’s top-scoring submarine ace, in which career he naturally used Whitehead torpedoes to sink English and Italian vessels (including an Italian submarine, Nereida, in possibly the first sub-on-sub torpedo battle in history).

You might have heard of the guy, who later emigrated to the United States with their kids after Agnes passed away. His name was Georg, Baron von Trapp.

What’s Safe Pressure in a Given Cartridge and Weapon?

Screenshot 2014-04-13 23.25.51We’re lifting this from Dan Cotterman’s Handloading column in the September/October, 1983, edition of American Handgunner magazine.

Dan, wherever he is, may well forgive us, because he in turn lifted the idea from Vern Speer (of Speer reloading fame), as he freely admits:

The late Vern Speer years ago worked out an uncomplicated and quite practical method for determining relative chamber pressures. Observing, and rightly so, that different guns produce pressures in differing amplitudes, and that test data from serious laboratories using pressure guns were often less than consistent, Spear said he’d discovered a more reliable process.

Acknowledging the fact that the cartridge case is the weakest link in the chain of components, he wrote:

“If the pressures at which these cartridge cases are fired do not exceed the elastic limit of the unsupported rim of the cartridge case, then we consider that the pressures are entirely usable, regardless of what they might be.

“We fire increased loads, increasing the charge by about a grain at a time, and check the rim diameter of the cartridge case with sensitive measuring instruments, both before and after firing. If any measurable increase in diameter of the rim of the case is noted, we consider that pressure is excessive, reduce the charge about 6 percent and list it as a maximum load in our loading table:”

Speer went on to acknowledge the value of looking for other signs of excess pressure (such as difficult extraction and flattened or cratered primers), in addition to measuring rim diameter. Note also that he cited “any measurable increase” as sufficient cause for reducing a load.

The foregoing may exist as a viable means of determining relative chamber pressures, especially for the home loader who does his work physically and financially removed from costly laboratory equipment.

That’s a sensible, simple, and practical means of setting maximum pressure when you’re developing loads. It might be a better method for using with pistols than with rifles; rifle bolts tend to provide much better case-head support than the usual pistol’s chamber does, and that case-head support might mask signs of increased pressure, especially the very subtle “any measurable increase” that Speer was looking for.

We also thought that the way Speer worded his comments suggests that he found this method not only, “safe enough to use,” but also superior to the supposed gold standard of firing in a pressure rifle. Of course, it’s not going to work with large caliber Glocks: even factory loads can bulge the cases in those!

The whole magazine, of course, is interesting, as it’s a time capsule from an era 30 years ago. In those days, American Handgunner was a bastion of revolver holdouts and 1911 fiends (in those days, we were all 1911 fiends), and covered the then-hot sport of metallic silhouette shooting.

The advertisements are our favorite part of any old magazine. In this one, they include revolver holsters and 1/3 moon clips, things that are much less popular today that they were then; aftermarket products like the Metaloy hard chrome refinish, which is still available but seems to have lost market and mind share; and products we don’t even remember knowing about at the time, like the .41 Avenger conversion kit for the 1911 from SSK Industries in Ohio. The 41 Avenger was a little bit before it’s time: the big idea was to combine the flat trajectory of the 9mm with 30% more energy. The idea’s time did come in the form of the 10 mm and the .40, but nobody remembers the .41 Avenger now. Well, we don’t. YMMV.

ATF Says Nyet to SIG MP-X-Carbine, SIG Sees ‘Em in Court

SIG MPX-CThe Bureau of Alcohol, Tobacco and Firearms has ruled that the muzzle brake for the SIG-Sauer MP-X Carbine model is “intended only for use” as a silencer. (We covered the introduction of the MP-X in January, 2013). The timeline of the whole SIG-ATF interaction also serves as an illustration for the glacial pace at which the payroll patriots of ATF do, or don’t do, just about anything:

  1. 4 Apr 2013: MPX-C submitted by SIG to ATF’s FIrearms Technology Branch (FTB)for evaluation.
  2. 26 Aug 2013: (note, 153 days later — ATF speed) FTB rules that the muzzle brake is a silencer. It is, says FTB, a “monolithic baffle stack. Welding it to a barrel does not change its characteristics or function.”
  3. 6 Sep 2013: (10 days later — private sector speed) SIG responds to ATF with the results of tests that show that the device does reduce recoil and muzzle rise, but that instead of silencing a weapon, the gadget the bozos at FTB think is a silencer actually increases the sound level of the rifle’s report. SIG also shows other examples of similar devices that have not been classified by the arbitrary FTB examiners as silencers — just SIGs. SIG’s letter includes comprehensive documentation.
  4. 21 Feb 2014: (141 days later — ATF speed) The FTB responds, ignoring but not disputing SIG’s evidence, and reasserting that the part looks like it might go in a silencer to FTB’s GED-level experts, therefore, it is a silencer. Amazingly, to the FTB, the fact that it does not silence, suppress, muffle, or reduce sound is irrelevant. So it’s a non-silencing silencer, and SIG can lump it.
  5. 7 Apr 2014: (47 days later — getting lawyers involved slows even the private sector down) SIG files suit in the US District Court of New Hampshire.

SIG’s is being represented by two excellent attorneys, NH’s Mark Rouvalis and Virginia-based national and international gun-law expert and legal author Stephen Halbrook.

SIG MPX-C-right

Although the technology exists to conduct clear and simple tests of suppressor noise reduction — one example protocol, developed by Dr Phil Dater, is used by the military — the ATF’s supposed experts at the Firearms Technology Branch don’t have this capability, and so they don’t evaluate items they think are suppressors or suppressor parts on it: instead, they eyeball the piece, based on their past training (which is in-house and shallow), and experience. They do not need to look at ATF precedents — FTB rulings are non-precedential, sometimes ephemeral, and each one is approached de novo. They are never retracted, unless they favor the applicant, and then they’re subject to a revocation process that’s as arbitrary and capricious as the original process was.

ATF may be relying on erroneous media reports, when the MPX was introduced, that the MPX-C muzzle brake was identical to the suppressor innards and “all you need to do is add a registered tube” to have the same suppressor.

But in a very similar case just last month, the US District Court for the District of Columbia ruled that the Innovator Enterprises “Stabilizer Brake” is not a suppressor, and that ATF’s method of guessing the effects of a device based on hunches and eyeballs is “arbitrary and capricious” and not a “reasonable construction” of the law. (Here’s the write-up of the case at Guns.com and at Courthousenews.com; here’s Innovator’s complaint; here’s the Court Ruling – the last two courtesy J Frazer Law).  The judge’s opinion is definitely worth reading; it looks like the Department of Justice attorneys played fast and loose with the truth.

 

Bullets with dimples?

Nammo Reduced Range

Nammo BNT 6 Reduced Range 7.62 x 51 mm

We all know that dimples can make a smile irresistible. But a bullet?

Nammo is making 7.62 x 51mm rounds with dimples, and it’s about their physical attraction — sort of. That’s if you’ll accept the meaning of “physical” as in “laws of physics,” and to be more specific, aerodynamics. By making the projectile more physically attractive to the air it passes through — sort of, reversing centuries on progress in making wind-cheating bullets — they can make rounds that work for training on tight, urban ranges.

The Nammo BNT 6 Reduced Range load contains a unique dimpled round weighing 6.2 grams or about 95.7 grains, so it’s very light for a 7.62 round. Its muzzle velocity is in the usual NATO ballpark at 860 m/s (2822 fps). At short ranges (<200m) Nammo claims that the round is equivalent to the usual NATO loads. But it spends its energy very rapidly and can be used in a range fan of only 1500m. (The standard NATO round demands a 4 kilometer range safety area minimum, without safety margins).

The dimples are the key. They are optimized for the round’s Reynolds Number and increase drag two ways, in terms of downrange motion, and, more critically, in terms of spin (which, if we’re doing the back-of-the-envelope right, implies two different RNs based on the different surface velocities). The increased drag and reduced weight make for a projectile that sheds its velocity (both rotational and longitudinal) much more rapidly than normal.

These are quite a different thing from the dimples used to increase the boundary-layer size and reduce drag on golf balls and some experimental target bullets. (Yes, that’s an April Fool’s spoof. And it fooled us on first reading).

Nammo BNT 6 in a belt. (Nammo photos).

Nammo BNT 6 in a belt. (Nammo photos).

BNT 6 is also available in standard links for MG training (including firing from vehicle crew positions), but at present, is only available in ball, not tracer. (A tracer and a “dim tracer” for use with night observation devices are in development). Like most recent Nammo introductions, BNT 6 is “green,” leaving no toxic contaminants behind. BNT stands for “Ball, Non-Toxic,” in the company’s nomenclature, and the BNT 6 projectile reportedly has a soft-steel core only. (Nammo’s combat-load BNT rounds have soft-steel cores with hardened-steel penetrators).

The technology could be adapted to 5.56, at least in theory, if Nammo had a customer for the reduced-range rounds.

Most of the demand for such a round is in Europe, where training areas are at a premium; several European ammo makers often reduced-range non-toxic rounds, although none of them are using the Nammo dimples. (Ruag, for example, uses a near-cylindrical copper round with a central spike). We were unable to find a patent filing for the BNT 6 style projectiles, but suspect one exists.

While the principal use for such reduced-range loads is training, Nammo points out that it’s also useful in urban-warfare and CT applications or “populated sensitive areas,” where minimizing the beaten zone of rounds that miss their targets is a priority.

NH Criminals use a higher class of gun than their MA cousins

That’s one of our take-aways from this report on the state crime lab.  While a lot of the crime lab is dedicated to drugs and toxicology,

Three walls of a room in the state crime lab’s criminalistic department are lined with guns seized from New Hampshire crime scenes, ranging from palm-sized pistols to a rocket launcher found in someone’s apartment.

There’s also a water tank, through which bullets are shot from suspect guns before the spent bullets are retrieved and compared to evidence found at crime scenes or in bodies.

Bullets are made “a hair larger” than their intended gun barrels, so they take on unique markings, Pifer explained.

Through electronic Leica microscopes, which display split images of the ballistics evidence next to test samples, scientists can reach eureka moments when evidence links a gun to a shooter. Sometimes the science is aimed at finding criminals, Pifer said, other times it’s to determine which of several police officers at a scene fired a shot.

Thanks to crime shows, most people have an idea (if an exaggerated idea) of what ballistics evidence can do. Most people don’t know, however, how easy it is to restore defaced serial numbers.

If serial numbers have been filed off of a gun, Pifer said, his lab technicians can often restore them. Fingerprints on triggers and ammo clips can be lifted, magnified, photographed and uploaded to a federal database for a nationwide search, he said.

And finally, you have this:

While meeting with colleagues from Massachusetts, Pifer said, he learned that because New Hampshire gun laws are more liberal, the quality of guns involved in crimes here are better. In Massachusetts, he said, lab scientists get guns “sometimes held together with duct tape” and they’re afraid to test fire them, he said.

via State lab uses science in fight against crime | SeacoastOnline.com.

We actually don’t buy that chain of causation, actually. There are quite a few reasons that the criminals of NH are demographically distinct from their brothers in crime to the south — one reason is that armed criminals are much more common in Massachusetts, where armed violent crime is punished mildly if at all.

Is a red dot better than iron sights — for a pistol?

Here's a Glock 17 with a TRijicon RMR, The guns in the study were the slightly smaller but similar G19

Here’s a Glock 17 with a TRijicon RMR, The guns in the study were the slightly smaller but similar G19

According to what appears to be a Norwich University undergraduate study from 2011 that was recently noted by Soldier Systems Daily, the answer is in and it’s a strong “yes.” From the report’s Executive Summary:

This project examined the comparative effectiveness of traditional iron pistol sights with Trijicon, Inc.’s red dot optic sight. Twenty-seven students from Norwich University participated by undergoing a simulated training course of fire using International Defensive Pistol Association (IDPA) silhouette targets for four different stages. Thirteen students used iron sights and 14 students used the optic. The results of the project indicated that there was a statistically significant difference favoring the optic for “hits on paper” in Stage 1 (15 yard slow fire) and for accuracy (hits near the center mass of the target) for all four stages of fire. 

Summarized Summary: more hits with the Trijicon RMR in Stage 1, and better hits in all stages.

The study is credited to James Ryan, apparently a student at the university, and Robin Adler, a professor of Justice Studies and Sociology.

While the summary led the report, and the statements made in the summary are well supported by the study data, at the end, the study reached three conclusions. The interesting thing is that we can only find support for two of the three in the findings and data. The conclusions were:

  1. This comparative pistol project indicated the Trijicon Inc.’s RMR was more effective than traditional iron sights.
  2. The results suggest that trainees in military and law enforcement specialties may gain proficiency more efficiently with the RMR.
  3. In addition the RMR is useful for seasoned professionals.

We find support for the first two conclusions in the study, but didn’t see anything at all to support the third. (We would expect that the RMR would be useful for pros — we’ve found it useful –but we could find nothing in the study itself that backs that statement up).

If this study is repeatable, we’re going to see more sights like the RMR on more handguns in the coming years. The key limitations of the study are that it was of short duration (one range day for each group) and very small groups (the control and experimental group were each 15 pistol shooters,  plus three alternates. Both groups were generated by random assignment, and about evenly split betwen complete novices and people with some shooting and/or pistol experience. In the end, 27 total students participated, 13 using three-dot iron sights and 14 using the RMR).  This experimental data set is too small to generate a high degree of confidence, but the group with the RMR steadily and consistently outshot the iron-sight group.

The pistols were otherwise identical Glock 19s. The targets were modified IDPA standard targets (the head was removed as a point-advantaged target, because the shooters were instructed to engage the targets only at center mass).

The small sample size meant that a result would have to be extremely disparate between the two groups to meet measures of statistical significance. The measure used judging the variance between teh groups’ mean scores in the stages was the non-parametric Mann-Whitney U.  In each of the four stages, the RMR group had more hits than the iron-sight group, but only on Stage 1 was the difference statistically significant. The measure used for evaluating overall accuracy was the chi-square, familiar to every survivor of freshman stats. The accuracy advantage of the RMR was statistically significant.

For both the mean scores in Stage 1 and the accuracy superiority overall, the probability of these results being the consequences of random chance, rather than an actual advantage of the RMR over iron sights, was 1 in 100.

WeaponsMan Analysis — Why the RMR “wins.”

The key advantage of the RMR on a pistol is the same as the key advantage of any optic on a rifle, compared to iron sights: it eliminates the need to consciously focus on one of three focal planes (the front sight) but allows a shooter to focus on the target and have the aimpoint superimposed in the same focal plane. A secondary advantage is the red-dot’s ability to compensate to some extent for poor presentation, pistol cant, etc., in ways that iron sights cannot.

The key disadvantage of the RMR is the way it juts out from the top of the pistol slide, making the pistol more awkward. While optical sights are often considered frail and vulnerable, the RMR  is a fairly robust unit, and a blow that would dislodge or damage it might well dislodge the standard three-dot iron sights also.

The full study can be read on SSD at this link or downloaded from here: 2011_Norwich_Study_RMRvIronSights.pdf

A 3D Printing Story

3d-printer-guide-0314-mdnThis story at Popular Mechanics is somewhat grandiosely titled, “Everything You Need to Know to Start 3-D Printing.” While it might not contain everything you need to know, it is a pretty good description of one guy’s trials and errors getting started, and it has a helpful sidebar that shows some of the currently available printers and their pros and cons. Here’s a taste:

Before investing in my own printer, I decided to get some experience on someone else’s. I asked around at my local co-working space, Tigerlabs, in Princeton, N.J., and found a tenant who let me use his MakerBot Replicator 2 in exchange for a couple of the rockets I hoped to make and a generous spool of printer filament (about $50).

3D printers build things by depositing successive layers of material, a process called additive manufacturing. Most use a mechanism that’s like a cross between an inkjet printer and a hot-glue gun: A plastic filament feeds into a heated printhead, which dispenses hot goo that quickly cools and hardens. Early homemade printers used replacement line from string trimmers as feedstock, but today’s machines run on specially made material.

Those serious about 3D printing use machines that handle all kinds of plastics, most commonly ABS (acrylonitrile butadiene styrene) and PLA (polylactic acid), but also materials such as nylon, fiber-reinforced plastics, and PET (polyethylene terephthalate) derived from recycled soda bottles. ABS is popular because it’s strong, inexpensive, and easily modified with tools after printing. On the downside, ABS emerges from the printhead as a thick syrup that flows slowly and shrinks as it cools, making high-precision printing a tricky affair.

It’s a short and pithy article so you’ll want to Read the Whole Thing™. the author,, is trying to make parts for model rockets; but with 3-D printing, the part you’re trying to make is less important than the technology you’re trying to use.

The author is not terribly experienced at 3-D printing, but that’s one of the things that makes this article useful; in our experience, people with a lot of 3-D printing experience tend to forget the unholy Frankenstein monsters they made in the early stages of their learning curve. People who are real additive manufacturing boosters, like us, also tend to be more willing to excuse the technology’s failures, flaws and foibles.

We walked off with some valuable takeaways from this article:

  • It pays to experiment with a borrowed or hired printer, before you commit to buying one.
  • There is no substitute for the knowledge gained by hands-on experience. (This is so near universal in its applicability, that it just may be a natural law).
  • This inference follows logically from the last conclusion: that the time to get started in this is right now.
  • Even the simple prints that he used quickly exceeded the capability of the closed-source printer he was using. (This is almost certainly a software problem, because the differences between the various plastic 3-D printers’ hardware are not that great).

The sidebar is a three-image slideshow with printers recommended for three levels of interest — hobbyist, maker, or entrepreneur. It is the first place we’ve heard of the CEL Robox, whose “printhead can be swapped out for a stylus cutter, a milling head, or a 3D scanner.” That sounds promising to us, although we think everybody understands you’re not going to have much luck milling steel with a machine made from plastic and aluminum, and a look at CEL’s website — their original product was a sort of universal power tool kit for home workshop types in Europe — indicates that, while the Robox is .

Like many of the new 3D Printers, the Robox was funded on Kickstarter. Kickstarter, Indiegogo, and similar websites are useful places to hang out to get a sense of what’s coming next in additive manufacturing, if you’re not ready to geek out on some of the resources we’ve mentioned previously. (That is a link to a google search of Weaponsman for “3D printing” — or it should be. We wrote this in a place that defaults to a foreign Google search engine so we may have handbuilt the query to Google.com wrong, let us know in the comments).

Via Robox, we learn that an Australian team is making 3D-printed horseshoes that conform perfectly to a horse’s hooves — “horse-thotics,” they’re calling ‘em. They don’t say how they’re doing it but since they mention titanium, it’s probably some form of laser sintering (DMLS or SLS, maybe). Will the soldier or cop of this century have a weapon that conforms to his own physiognomy? We live, friends, in interesting times!

Resource: Armalite Tech Notes

ArmaLite logo sm.pdfOn Armalite’s website, they have a section of Tech Notes which is quite useful. Of course, it’s intended to help them sell their AR clones and other rifles, but a lot of it is of quite general application for and by anybody.

For example, they have a useful Tech Note on how to analyze performance claims in rifle marketing materials. Here’s an excerpt from that on accuracy:

Let’s say that three manufacturers (Companies AAA, BBB, and CCC) each produce 1000 M16A1 rifles. All three companies test their rifles under identical conditions. Each rifle is fired one 10-shot group with M855 military ball ammunition from a return-to-battery rest in a benign indoor range. Based on the testing, each company writes a marketing ad.

  • Company AAA claims that their rifles fire groups as small as 1.5 MOA. {Best case}
  • Company BBB claims that, on the average, their rifles fire groups of 2.2 MOA. {Average case}
  • Company CCC claims that every one of their rifles will shoot groups smaller than 4.8 MOA. {Worst case}

If you were going to purchase a rifle, which company’s rifle would you choose. (You don’t get to “hand select” the rifle. You just get a random rifle from that manufacturer.)

The reality is that the rifles built from all three manufacturers are probably all quite similar. In order to guarantee that all 1000 rifles will meet or better 4.8 MOA (Company CCC’s claim), the average rifle needs to shoot about 2.2 MOA (Company BBB’s claim) and the best rifles probably shoot about 1.5 MOA (Company AAA’s claim.)

In fact, the Army required that EVERY M16A1 rifle delivered to them meet 4.8 MOA. In order to meet that requirement, manufacturers found that they needed to produce rifles that averaged about 2.2 MOA, and that their best rifles would often shoot about 1.5 MOA.

In the example above, Armalite says, they give their averages as data, but they do point out that without more information, even an average makes comparisons impossible. You need more information. A statistically-educated man would be able to make a comparison of two tests made under equivalent conditions, if he had the average and Standard Deviation, or some measure of variance that could be massaged into SD.. Of course, a true data geek would want to see the entire cross-tabs on the whole test population. 

An even more useful tech note is from Armalite honcho Mark Westrom, and evaluates hits vs. firing rate. It’s hard to choose what to excerpt from this very interesting paper, so we’re tempted to just tell you to Read The Whole Thing™, but here’s one pearl of wisdom:

Consider a soldier armed with a weapon with an endless supply of both ammunition and targets. He may fire a single shot in a given time period (i.e. one minute) and have a certain chance of hitting the target. He may also choose to fire two shots in that minute. The two shots are apt to be aimed less accurately than a single shot because of the time allowed, but the probability of achieving at least one hit is increased because two shots were fired. The efficiency of ammunition use may have declined, but the probability of achieving at least one hit has risen. With each additional shot in that minute the accuracy of each shot will tend to decline, but the number of hits expected in the minute will continue to rise. Eventually the shooter is firing so fast, and the shots are so wild, that the number of hits starts dropping. The various theories of efficiency of marksmanship appear at different places on the curve thus generated, and their logic and usefulness can be evaluated from a standpoint that means more than a traditional percentage score.

This concept is by no means new. It is, as the saying goes, intuitively obvious to the casual observer. One Nineteenth Century writer noted that, “as rapidity of fire increases, a point is soon reached beyond which the percentages of hits decrease…but up to that point at which carelessness or hurry in aiming causes an excessive decrease in the percentages, the whole number of hits may increase” (emphasis added).

Screenshot 2014-03-09 16.07.16

The area of the curve at the far left of figure 4, region A, provides the most efficient use of ammunition, and it would appeal to the traditional marksman and his slow fire techniques. It’s also useful to the contemporary soldier who has a limited supply of ammunition….

On the other hand, a soldier who chances upon another opponent, or group of opponents, may not care how much ammunition remains at the end of a minute. He cares whether he remains at the end of the minute. …This man would employ rapid semiautomatic fire to operate in the higher parts of the curve, region B, where casualties are produced fastest.

Areas of the curve to the left produce maximum casualties per unit of ammunition. Areas at the top of the curve produce maximum casualties per unit of time. The area of the curve where hits per minute starts to drop off, region C, represents less efficient use of both ammunition and time, and represents increasingly ineffective firing technique unless intended as suppressive, area fire.

…and here’s another, relating to the first (and heavily edited for brevity)

Once the issues related to the curve are understood, we should develop those talents, conditions, or actions that increase the hit rate, i.e. raise the curve. A number of possibilities appear useful

Aim every shot. Even machineguns must be sighted if at all possible. There can be no exceptions for blanks.

Make it a Tradition. Aiming every shot should not be a training imperative: it should be a tradition. Rifle cleaning provides an interesting example of a task that is raised to a tradition.

Establishing a tradition of aiming every shot rests properly with the NCO Corps. From the first day a soldier or Marine handles a rifle, he should be driven to bring the rifle to the firing position every time he pulls a trigger, whether in training or merely lowering the hammer to turn the rifle in to the arms room.

Support the tradition in training. Current training teaches the wrong lessons. Each target is addressed by one cartridge. The correction to this is simple. Issue sufficient ammunition to allow for misses. Reward the shooter based on targets ultimately hit. Reward him further with a few points based on ammunition remaining. The highest scores obviously continue to go to the best shots, who both hit many targets and return with ammunition, but all are trained to engage.

Avoid burst or automatic fire. It is essentially useful for room to room fighting or trench clearing. Three shot burst if largely useless for both close combat and longer range fighting. It is truly the worst of both worlds. Both automatic fire with the M-16A1 and Burst fire with the M-16A2 should be strenuously discouraged by the same NCOs who reinforce the act of aiming every shot. This is especially important during training with blanks, because soldiers enjoy automatic fire as a matter of play…

So now go Read The Whole Thing™.