Category Archives: Rifles and Carbines

Snap, Crackle, and Pop

Well-known (and respected) trainer Kyle Defoor was conducting training at for a military unit when one of the unit’s long guns went down, due to this:

defoor bolt failure

Yes, that’s an AR/M16/M4 bolt with a single lug fully failed. Possible causes for the failure include (at a fundamental level) manufacturing error, corrosion or fatigue. It’s hard to judge from this hole, but going way out on a limb, it looks like there’s a somewhat granular failure at the left end of the fracture, with a smoother “sudden” fracture face on the right end nearer the extractor, presumably because the fatigue failure left too little of the remaining metal to bear the stress of firing locked in battery, and the remainder of the part failed from the crack due to overstress. But it could also be caused by swapping a fresh bolt into a gun with a worn barrel extension (or vice versa) in the field, so that only one lug was bearing all the tension of locking — result, failure. Or the gun may simply have been made without the locking lugs all engaging properly — it’s happened before.

A gun with a failure like this may or may not continue to fire for a while. But if overstress on one lug was a factor, the loads formerly too much for seven lugs now bear upon six — it would not be wise to bet your life on this firearm.

Kyle, though, had another issue with the failure — and the unit whose arms room coughed up the firearm that did it.

On 9 July, he posted this image to his Facebook feed, saying:

Maybe I should start to amend contracts to include an armorer and spare parts?

With a hilarious set of hastags including, but not limited to:

#‎takecareofgear‬ ‪#‎ittakescareofyou‬ ‪

…and the snark-infused:

‬ ‪#‎logisticswinswars‬ ‪#‎waistingtrainingtime‬ ‪#‎youdontpaymetoplumb‬

The part was, as you can see from the markings, a factory Colt, magnetic particle inspected, bolt (or a counterfeit thereof that somehow got into the supply system — not impossible). It had unknown hours and rounds, because Big Green is not in the habit of keeping meaningful usage and maintenance records on small arms.

Apart from spelling “wasting” wrong, there is not much to argue with in Defoor’s response. Apparently the unit in question did not provide an armorer for the range event. In most units, the armorer doubles as a supply clerk and is not thought of as necessary for a range evolution (except to manage draw and turn-in of weapons at the Arms Room). In addition, the Army has been working to reduce the number and kind of spare parts available at organizational level. This is due to politically anti-gun policies, and Army civilian political appointees who believe (however lacking the evidence may be) that Army stocks are a significant source of crime guns.

Even if the parts were by some miracle on hand, the standard Army armorer, one each, is neither trained nor authorized to replace a failed bolt. Armorers given scant and cursory training on maintenance.  Instead, their course, an add-on for supply clerks, concentrates very extensively on paperwork, records-keeping, and the process of appearing to be conducting scheduled maintenance. This is also borne out by what actual combat units and their commanders value, based on how they judge and critique their armorers. No one is ever graded on the only maintenance measure that ought to count, the combat serviceability of the unit’s firearms; everyone is constantly graded on the process, on the appearance of maintenance, and on maintenance busy work. While we’d bet nine out of ten of the readers of this blog could fix this rifle in minutes, the only thing a company, battalion or even brigade armorer can do with it is turn it in.

Military maintenance bureaucracy does all it can to limit effective maintenance of small-unit equipment, notably including small arms, optics, and radios. Problems with these are most effectively solved by trained, experienced personnel at the lowest organizational level, so naturally such personnel are just flat not available.

Instead, you must tag the weapon or other piece of equipment down. Naturally, there are different rules for weapons and weapons equipment, vehicles, radios, and special weapons (i.e. WMD-related stuff), although the Army does try to squeeze them all onto standard forms (DA-2404 for regular maintenance, DA-2407 for turn in, nowadays it’s an electronic form, DA-2407E, done in the SAMS logistics computer system).

The weapon can’t be sent directly to the level that can fix it, even when (like this) the level is obvious and the weapon could be inspected and classified by a well-coached Helen Keller. It must go up the operator-organizational-direct-depot support chain, getting a new inspection at each

Plus, while the weapon is turned in, what is Joe Snuffy supposed to shoot? No Army unit maintains operational floats or spares (unless it is, by happenstance, or the customary incompetence of all Army personnel managers and activities, understrength). So Joe will get the weapon of whoever is on sick call or leave when the unit goes to a range, unless it’s one of the very large number of units that does an absolutely crap job of tracking who is assigned each particular weapon, in which case it’s musical chairs and the last one that shows up gets a new weapon.

The Army actually tries to bill giving a guy a new rifle for every annual, semiannual or quarterly trip to the range as a plus, believe it or not: “Everybody gets valuable experience in zeroing.” (Meanwhile, of course, everyone loses confidence in the ability of his gun to hold zero).

It does not help that the standard M12 rack does not accept a rifle with optics. In the Arms Room, it’s still 1988.

Moreover, the Army’s weapons records are a chaotic mess of rack numbers, serial numbers, weapons cards, hand receipts, pencil sheets, green-and-white property book printouts (that may not put all your unit’s rifles, for example, together on the same pages), and unofficial Excel-spreadsheets and Access databases, which interface more or less (mostly, less) with one another and with the unit’s personnel assignments. This means that every time you cross-level personnel from 2nd platoon to 3rd platoon, if your arms room is nicely organized by platoons, Joe Rifleman is going to get a new rifle and be off zero until next range trip, and so is Bill Bulletician who’s coming from somewhere else… that’s another reason why no Army unit beyond the Ranger battalions and the 82nd Division Ready Battalion actually dares to ship out to combat without a trip to the zero range.

In addition to the deployment delays that come because no one has confidence in his optic zero right now, we also endure a colossal waste of time because weapons inventories are unnecessarily hard. (One of the nice things about HK 416s? Their serial numbers are highlighted. Seems like a small thing, until you’ve tried to inventory a couple hundred M16A2s by the light of a flickering fluorescent bulb that there’s no budget to replace. And if you highlight the number with paint or permanent marker, you can actually get dinged on inspection). Every arms room needs to be inventoried periodically by senior personnel who have better things to do, and many aperiodic inventories are demanded by regulations. The faster these go, the better for everyone, but the Army has a settled way of doing things that proceeds from the assumption that the net value of a soldier, NCO or officer’s time is always zero.


Testing Polymer Receivers to Destruction: Factory and Printed

Here’s another embedded video from’s InRange TV, where Ian and Karl do their level best to destroy a Cav Arms polymer lower.

They step on it, stomp on it, run it over with a Jeep, and shoot holes in it, and still it keeps on shooting. One is reminded of the old Timex ads, “Takes a licking and keeps on ticking.” Maybe it should be “Takes a drilling and it keeps on killing (IPSC targets).”

We’re not really shocked by this. We had AKs and SKSes in the foreign weapons arms room in 10th Group that were Vietnam captures, complete with bullet and claymore holes, and they all worked. (We kind of doubt their previous owner Mr Nguyen was still in such adequate operating condition). And we’ve seen ARs take some pretty brutal treatment and keep on shooting, including carbines that would still chamber rounds after their plastic was all burned off and their magazines blown out by a helicopter post-crash fire (we didn’t shoot them, though), and an M16A1 that still functioned (albeit inaccurately) with the barrel bent 30º off axis at the FSB1 (it was under a trooper’s armpit when he executed a really craptacular PLF2, dislocating his arm and bending the rifle).

A really good design is overwrought enough that it can be degraded by wear, corrosion, or, yes, combat, a good bit before it fails to function. And a really outstanding design delivers that with the smallest weight and bulk penalty possible.

Cav Arms made quite a few of these lowers out of durable Nylon 6 before the company was singled out for destruction by the ATF, which is a long story and off this topic. (A seemingly complete technical history of the Cav Arms lower has been prepared by Russel Phagan, aka Sinistral Rifleman, who assisted in the video). A successor manufactures the lowers today. (But the most significant thing about the lower wasn’t the company’s grim fate; it was that the lower was redesigned from the ground up to be made of polymer, to take advantage of this material’s strengths, and to shore up its weaknesses).

As Ian points out towards the end of the video, a polymer lower designed to be a polymer lower is a better bet than one that is just a molding of the traditional 7075 alloy machined forging. (Conversely, a steel receiver that follows the form factor of the alloy lower is going to be overstrength and overweight). These follow from the differences in the strengths of the three materials.

Ian notes the weakness of the buffer tower if the normal lower receiver is modeled in anything other than metal, and that gibes with the results that early lower-receiver 3D printers had, substituting much weaker ABS or PLA material for the 7075. The first point of failure to be made manifest was the buffer tower area. This led to reinforced buffer towers and ultimately such heavily-reinforced lower-receiver designs as the modern Aliamanu-Phobos.


Along with the reinforcements named in that slide, the massively reinforced buffer tower is evident. But even this beefy design can fail. This one started to delaminate with just 20 rounds fired. Test firing the lower:

trouble1 aliamanu-phobosHere’s the first image of the delamination. Since all the fire control group parts are above the delamination line, the weapon should still operate, but this obviously bodes ill for any probability of it surviving further testing. (Yes, these do embiggen for more of a close-up look).

trouble1 delamination 1Here’s the other side at that 20-round point:

trouble1 delamination 2


Firing more rounds just cause more failure, in this case it seems that the area around the grip screw also began to delaminate, releasing the grip:

trouble1 delamination 3At this point, stick a fork in it, it’s done.

Others have had much better results, including from pretty low end perimeters, and the equipment and parameters that FOSSCAD member trouble1 used didn’t seem out of step with what the successful printers did. But you can’t call this a successful print. It seems highly probable that there is some failure in the print setup or materials (moisture in the filament?) that no one has figured out yet.

That delamination is an interesting failure mode that’s fairly common in fused filament fabrication printing, is only one reason the technology is not yet ready to compete head-to-head with plastic injection molding. The much slower production of the additive process, and its higher per-unit variable cost, also argue against this for production. However, injection molding, with its generally higher fixed costs (for tooling), is unsuitable for prototyping and very short production runs. A hybrid of technologies that uses printed molds to reduce that fixed cost for short runs offers the potential of closing the gap. But a proper part is a part that is designed in conjunction with its manufacturing technology — engineered for production from Day One, with materials  chosen to meet the mission and simplify, speed up, and save money on production.

As Ian noted about the Cav Arms polymer lower (which is injection molded), it’s necessary to design the part to make best use of the materials and technology. Simply trying to reverse-engineer a popular firearm in a new material or manufacturing approach will only take you so far. It may, given enough iterations, be far enough.


  1. FSB = Front Sight Base, the triangular-shaped forging that holds up the front sight on the nose of AR-15 series rifles through the early M4A1. It also locates the gas tube and hosts the bayonet lug — a busy small part.
  2. PLF = Parachute Landing Fall, a specific roll that reduces the risk of injury when a para touches down.

Do We Need A Bigger Bullet?

Jim Schatz, former HK USA manager (during the period of peak Because-You-Suck-And-We-Hate-You customer service, actually) always has one of the most interesting presentations when he’s up at an NDIA1 conference. The slides from this years’ NDIA are up (here), and Jim’s presentation, interesting as ever, is up here (.pdf). Jim wants us launching bigger bullets, to longer ranges.

Jim’s basic beef is probably best encapsulated in this quote from an SF team sergeant:

Few enemies would even consider taking America on in a naval, air or tank battle but every bad actor with an AK will engage with U.S. forces without even a second thought.

To boil down his argument to a single-sentence thesis: The US lacks small-arms overmatch, and only changing cartridges can get it for us. He defines overmatch by effective range. As he sees it, this is what the world looks like today:


As a former infantryman, Jim knows that weapons don’t square off one-against-one. On the battlefield, units from corps to squad size all maneuver to bring their organic, attached and support firepower to bear on the enemy (who is doing the same, inversely). It’s a common fallacy that (for example) because every squad in the Ruritanian army has a designated marksman, our squads should have one too. (Maybe they should, but not directly because of what the Ruritanians are doing). As you can see, Jim’s focus on range leads him to pair off sniper rifles with light machine guns, weapons which have similar effective ranges for completely different reasons, even when they fire dimensionally identical ammo.

As far as his 1000m effective range of the SVD is concerned… he must have shot one?

Here is one of his proposals for overmatch. There’s a few things screwy here (the SVD has grown  an even-more-ludicrous 500m of range, to 1500m), but that’s not important. What is important is the argument that going to an Intermediate Caliber Cartridge (something like the 6.5 or 6.8 or something all new in the 6-7mm neighborhood) for rifles and to .338 for support weapons will provide significant range overmatch.


The increased ammo weight can be made up in part by polymer or semi-polymer (i.e. with a metallic base) cases.

Jim at least partially neutralizes the cost-in-times-of-drawdown argument by suggesting that the new weapons go only to the tip of the spear, the guys whose mission it is to produce casualties, and take and hold ground, with these weapons. That’s only about 140k actual shooters out of the much larger service. A finance clerk needs a rifle, sure, but he or she can live with the latest-but-one.

Bear in mind that the target set is also not static, while we’re developing all these new weapons the Russians, the Chinese, and even the ragtag insurgents of the world (who have definitely, like Russia, pushed more 7.62mm weapons down to squad-equivalent level than heretofore) are acting, adapting, and changing, too. We don’t need to overmatch the enemy today with the weapons we’ll have in ten years. We need to overmatch the set of weapons the enemy will have ten years from now, in ten years.

Men can disagree about how best to get there. Assuming we stick with the M16/M4 platform, Our Traveling Reporter would have us go to the 6.8 x 43. (It was news to him that the Saudi Royal Guard has adopted this platform, in LWRC carbines, or that military 6.8 is in production for export now by Federal — formerly ATK). We would probably go with the 6.5 (x38, although the length designator is seldom spoken aloud) Grendel for its lower BC and higher sectional density (=longer effective range, flatter trajectory, more energy on target). The 90 grain Federal load in the 6.8 is very effective closer in (the 6.8 was developed with SF input as a CQB cartridge).

Some current contenders --  M855A1 5.56; 6.5 Grendel; 6.8 SPC; 7.62 NATO. From an excellent article by Anthony Williams setting out the historical context.

Some current contenders — M855A1 5.56; 6.5 Grendel; 6.8 SPC; 7.62 NATO. From an excellent article by Anthony Williams setting out assault rifle ammo in historical context, including many old, obscure, and outright forgotten attempts. Shape of the 6.5 suggests a superior BC. The 6.8 is compromised by its 5.56 ancestry and packaging (bolt head size/overall length).

This is not an entirely new or novel idea. As mentioned in the caption to the photo above, British researcher Anthony Williams has a very fine article on Assault Rifle History with lots and lots of ammunition comparison photos. Back in the 1970s, a guy whose business was called Old Sarge, based in the highway intersection of Lytle, Texas, made a quantity of 6 x 45 guns and uppers. Based closely on the 5.56, these guns (most of them were built as what we’d now call carbines) were completely conventional, but like today’s 6.8 SPC the intent was to create superior terminal ballistics. We don’t know what happened to him or what seemed to be, when we stopped in, his one-man business (he talked us out of a mod he’d done for others, an M60 bipod on an XM177).

If we have a serious criticism of Schatz’s work here, it’s that its focus solely on range as an indicator of overmatch understates the problem. Hadji with his AK and mandress has a lack of fear of our troops that stems only partly from his belief that range makes him safe (and only partly from his paradise-bound indifference to being safe). His feeling of impunity stems from a belief he won’t be engaged at all, won’t be hit if engaged, and won’t be killed or suffer significantly if hit. We need to increase the certainty that our guys will fire back, not just increase our pH, and we need to increase our pK as well. The first of these is far outside the scope of weapons and ammunition design, but it is, in our view, the most serious shortfall of US and Allied forces.

We have another beef that’s not specific to this, but that arise with any attempt to pursue range or other small-arms overmatch: it never works. There are only two ways pursuit of overmatch can finish. Either your new weapon does not constitute an overwhelming advantage, or it does — in which case everybody copies it most ricky-tick. Mikhail Kalashnikov died bothered by the fact that he never got royalties on any of the millions and millions of AKs made outside of his homeland, but the guys who really got copied were the engineers who built the StG.44. (True, the AK was better adapted to Soviet expectations, traditions, manufacturing capabilities, and training modes, but it was certainly inspired, conceptually, by the first assault rifle). It was a good idea. It was exclusive to Germany for mere months (of course, that they were losing the war may be a factor, but that the war ended was certainly a factor in slowing the adoption of assault rifles in Russia (a little) and the West (a lot).

In all seriousness, if you look at the history of firearms, you see a punctuated equilibrium. For centuries the flintlock is the infantry weapon, then the percussion lock sweeps the flints away in a period of 30 years or so (faster for major powers, or anybody actively at war). Then the breechloader dethrones the percussion rifle-musket in a couple of decades… to itself be overthrown by repeaters in 10 to 20 years. Calibers go from 11-13 mm to 7-8 mm to 5-6 mm at the same time all over the world. We’ve had a very long period now of equilibrium around the SCHV (Small Caliber, High Velocity) concept. Is it time for that equilibrium to be punctuated? Schatz says yes.


  1. NDIA: National Defense Industrial Association, a trade and lobbying group for defense contractors. Formerly the American Defense Preparedness Association (when Your Humble Blogger was a member, and they were fighting a rear-guard action to preserve a defense industrial base during the Clinton disarmament/drawdown cycle), and before that the Ordnance Association.


Daniau, Emeric. Toward a 600 M Lightweight General Purpose Cartridge. September 2014. Retrieved from: ; this is a uniquely French view of this same challenge, hosted online by Anthony Williams.

Schatz, Jim. Where to Now? 3 June 2015. Retrieved from:

Williams, Anthony. Assault Rifles and Ammunition: History and Prospects. Nov 2014. Retrieved from:

Williams, Anthony. The Case for a General-Purpose Rifle and Machine Gun Cartridge (GPC). Nov 2014. Retrieved from: ; an earlier version was presented at NDIA in 2010:

(Note that Williams’s work on this matter was sponsored by H&K, a fact that is not invariably disclosed in all documents but that Williams publicly discloses on his website).


Meet the Gladius

ga_precision_logoRecently, a friend commented, to a third guy looking for an accurate rifle cheap, that cheap wasn’t the right way to do it.

“Look at GA Precision. George builds really accurate rifles. And he guarantees them.”  George is George Gardner, who founded GA Precision in 2007 and has built it into a thriving business that supplies a who’s who of long-range target shooters and law enforcement Must Not Miss Ever marksmen. And yes, George guarantees them:

G.A. Precision guarantees the accuracy of its rifles to be 1/2 MOA at 100 yards with match grade ammunition. This guarantee applies to any complete build or partial builds where G.A. Precision both barrels the rifle in combination with bedding it. As long as GAP agrees that supplied components are quality.

There are some exceptions for this. The Templar-action Crusader model is guaranted to shot 3/4 3/8 MOA and the GAP-10 7.62-NATO-caliber AR variant, 1 MOA — all with match grade ammunition. And the Non Typical Hunting Rifle, a build with a much lighter barrel for field use than a typical target or sniper rifle, is guaranteed to shoot to 1/2 MOA, but only for three shots (due to our oft-discussed bugbear, barrel heating, a bigger issue in a hunting barrel).

We’re pretty sure we’ve talked about GA Precision’s rifles before — friends of ours who came from a Marine Scout/Sniper background and continued their service under different sponsorship, shall we say, like ’em — but we thought we’d take a look, and we found one we really liked, the Gladius. (The name came from Frank Galli of Sniper’s Hide, it’s a Roman twist on GA Precision’s usual Crusades-themed gun names)


The Gladius is designed from the outset to be suppressed. It comes with the muzzle brake/ suppressor mount for Surefire systems. It has a short barrel (hence the name!) but still comes with the 1/2 MOA guarantee.


Now, if you are asking, as our friend did, for a “cheap” accurate AR-10 clone, GA Precision probably is not where you want to shop. Even their gas gun (reasonably priced for its quality) is a $3,000 system before optics and suppression, and a bolt gun like the Gladius is $4k plus, similarly bare of the glass and can that it will wear when fully dressed. (The glass can easily match the gun dollar-for-dollar, if you want the best brand names).

But if true precision is what you’re seeking, this is what it looks like. This is what it costs.

GA Precision has wait lists for most of its firearms (a few built-on-spec or customer-remorse firearms are always available on the site, but a popular one doesn’t stay there long).

The GA Precision website also contains a true illustration of what a class act George (and the company) is. Employees are listed on a Meet the Team page, but when employees leave in good standing their bios move to the Alumni page, and they’re remembered. Even George’s ex-K9 Malinois, Rocky, gets the Alumnus treatment.

To twist the tagline of some long-gone chicken farmer, it takes some tender guys to make a tough precision rifle.


This post has been corrected. We originally stated, incorrectly, that the guarantee on The Crusader was 3/4 MOA. While 3/4 MOA is pretty good (especially for a guaranteed performance with, not custom loads, but factory-loaded Match ammo), the Crusader is in fact guaranteed to 3/8 MOA, a much smaller (and tougher-to-guarantee) group.

We regret the error and apologize to the fine folks at GA Precision.

We also regret that we were unclear about the reason Rocky is on the Alumni page. While the other Alumni have gone on to other jobs, careers, or locations, Rocky has gone to the Great Dog Park Beyond. He’s baying in the Pack Invisible. He is an ex-dog — but warmly remembered, as anyone who has ever loved one would understand. The ancient Greeks believed that as long as one man remembered you, your spirit lived yet. Ave atque vale, Rocky (yes, we’re mixing Greek culture with Latin sentiment, so what? Go ahead and sue us, and find a blog that keeps thing Classically correct).

It’s oh-dark-hundred here and tomorrow’s posts may lag. Still trying to rescue a tech investment and playing Can This Company Be Saved? is time-consuming.

Geissele (ALG Defense) AK Trigger

Bill Geissele’s wife’s company, ALG Defense, makes products for more of a mass-market than the very sweet, fairly simple, Geissele AR-15 triggers that live in more than a few SOF M4s and Mk. 11/12/18s, etc. (Indeed, sometimes the Geisele triggers are authorized MFP 11 or unit purchases, and sometimes they are installed on a catch-me-F-me basis by unit weapons men or armorers). Along with the triggers for full-on M4s and HK416s, Geissele makes improved triggers in both single-stage and two-stage variants for a wide range of semi ARs. They’re not cheap, they’re not always in stock, but they’re good.

ALG Defense makes simpler AR triggers — and now, an AK trigger, imaginatively coded AKT. In this video Bill explains the objectives this trigger meets and talks about some of the challenges involved in designing it.

The AK, Bill says, “has a ton of sear engagement.” That’s what you, the shooter, perceive as the very long and very smooth takeup of the typical AK trigger.  (The SKS trigger has a similarly long, smooth engagement, suggesting that this may have been a standing Soviet / Russian design objective).

The result is an AK trigger that fits a variety of common receivers on domestic, imported, and kit-built AKs, and that reduces the trigger pull force and duration (including that all important very long sear dwell) significantly.

For example, Bill shows a graph of a stock AK trigger versus the ALG AKT; the stock trigger moves about 0.150″/4mm and takes about 4.5-5 lb. of pressure during that sear dwell period. The AKT takes up the slack more quickly and seems to come in about 0.065″ and just under 3.5 lb.

At about 8:30 he shows a 3D model (in Autodesk Inventor) of the trigger and walks through its function.

It fits some AKs with no fitting, but because of the wide variation in AK safeties, some AKs need a roll pin positioned so as to contact the safety. It’s explained in the video and in the AKT’s instructions.


Bubba Retros a Rifle

This thread in Imgur (and there’s a matching discussion on Reddit) shows the whole process of Bubba attempting to alter a modern AR receiver to more closely resemble a Vietnam War early Colt Model 603, often erroneously referred to as an XM16E11. He didn’t go all the way with it, opting not to reprofile the buffer tower and pivot pin areas, both of which were extensively reinforced in later AR lowers.  He did wind up with a decent-looking 50-footer:

Bubba AR

As you might expect, a Dremel2 was involved.

Bubba AR Dremel 02

What could possibly go wrong? Hey, it’ll buff out.  And it’s nothing a couple of rattle-cans of Rustoleum grey primer won’t cover.

Well, almost cover:

Bubba AR spraypaint

Lesson learned, by this Bubba:

Bubba AR Filing

Use a file next time!

His further lessons learned:

Sub /r/RetroAR.

Build retro rifles.


Be happy.

One of his reasons for doing this was that an NDS lower (which comes with all the profiling correct) was too much money. But on the positive side, he’s done non-irreversible damage to a cheap, generic AR lower, and he’s learned a lot. And if he’s like most Retro AR enthusiasts, every time he looks at that rifle it’s going to bug him until he gets around to improving it some more.

So maybe it’s possible for Bubba to educate himself clean out of Bubbahood. He’s learned, at least, that it’s easier to feel what you’re doing with a file than a Dremel, and that an ordinary Joe can take a piece of aluminum and bend it to his will.


  1. The label XM16E1 was used prior to the M16A1 type classification being approved, and was not related in any way to the change from a partial fence to a full fence lower receiver, which actually happened almost two years earlier, so you do see the XM16E1 roll mark on full-fence lowers.
  2. DREMEL: Device Removes Excessive Metal Electrically, Lummox.

Those Who Forget the Past, AR-15 Edition

A couple of days ago we followed a link from The Gun Feed to the Michigan-based gun blog 248 (We’re guessing 248 is an MI area code? The way the Workshop Eating Plane® will have “603” in its N Number?). Anyway, the article was a short and to the point gear review of an extended or enhanced mag release that is made by a company called ArmaSpec.

ArmaSpec mag release

Armaspec calls it the “Tactical Combat Button,” and says (right there on the package!) that it gives you “faster magazine changes.” It’s reminiscent of popular extended or enhanced mag catches that have become common on sidearms, like the Vickers Tactical catch we have in our Glock 17. (We’ve got the slide release, too. Larry is a hero to those of us with small hands).

Apart from the name, which gnaws at us in its jejune buzzwordiness (not “tactical” again! And “combat?” Whose?), it illustrates the problem of living in Baby Duck World, where All Things Are Ever New™. This button may be useful for someone running very stylized match stages, but it probably isn’t.

Here are our problems with the TCB, conceptually:

  1. First, there’s nothing wrong with the standard mag catch;
  2. Unlike the standard mag catch, this is very prone to unintended mag release;
  3. Unlike the standard mag catch, this cannot be installed, removed or adjusted without tools;
  4. In fact, it needs a peculiar tool which the rubber-meets-the-road system operator may not have on his person;
  5. It gives up most if not all the adjustability of the standard catch;
  6. It introduces additional points of failure into a proven subsystem;
  7. It is vulnerable to the screws backing out and requires Loctite to work at all.

Note that we haven’t tried this part ourselves, we’re just cueing off 248Shooters’ review.

The History of the AR-15 / M16 Mag Catch

The M16 magazine catch started as the AR-15 one, which, of course, began as the AR-10 magazine catch, as shown here. (The first shot is Serial #38, auctioned by James D. Julia some time past; the others are from an Portuguese AR-10 on an H&H Semi receiver). We have not tested the interchangeability of these catches, but we suspect that the AR-10 and -15 catches are the same length on the X Axis (front to rear) but the AR-10 catch is longer on the Y Axis (left to right).

Julia AR-10 #38 serial ar-10_porto_right_side_receiver_rotated H&H AR-10 02

The AR-10 magazine catch was not created in a vacuum. It itself was an improvement of the catch used in the seminal German MP44 assault rifle (We use “MP44” somewhat expansively here; the magazine catch appears to us to be the same in all related versions of the German assault rifle, back to the MKb 42 (H)). The direction of the release changed, and it was moved closer to the pistol grip, so that it could be released with the index finger of the right hand, instead of using the left hand as was done with the MP44. The next photos are of a Japanese non-firing replica of the MP44 (they were the clearest photos handy on the net). The mag release is the conical, ribbed button at the rear of the mgazine well.


This next picture shows a weakness of the MP44 system, which the AR system improved materially. As you can see, the catch, button and shaft are joined semipermanently by staking or riveting. That means it’s not field-repairable, let alone, -adjustable, at the -10 or -20 (operator or organizational repair, i.e. unit armorer) echelons. Again, this is a replica, but a very nice one.


By making the AR-10 design a one-piece shaft and catch, where the shaft threaded into a tapped blind hole in the mag-release button, Stoner made it possible for the magazine catch to be disassembled for repair, replacement or adjustment without tools. All you need is a cartridge to overextend the mag release so that the catch clears the magwell, and then it can be screwed in or out. On any AR, a mag catch that’s too “grippy” can be fixed by backing off a couple half turns, and one that’s kind of loose can be tightened up the same way. This adjustment can clear up a lot of “mystery” failures to feed in AR systems.

The magazine catch can’t unscrew itself without being overextended until it’s clear of the magwell, because the magwell holds the catch in place and prevents it from rotating. But as ingenious as the AR-10 magazine catch was, there were still two improvements to come.

The first was to exchange the blind hole of the AR-10 magazine release for a through hole. This made the magazine catch button much easier to manufacture and increased the usable range of adjustment for the magazine catch, with no downsides at all. From this alteration somewhere around 1960, the parts of the standard AR magazine catch are fundamentally unaltered until today. (One change is that the ribbing on the catch is circular, whilst in the early sixties it was straight and horizontal, but this is a cosmetic change driven by production convenience and not material to the function of the catch.

The 17 prototypes made all had a magazine catch that worked much like it has on all the milios of aRs since then. Here is Prototype 004, from the Reed Knight collection:

AR-15 Proto000004

The initial catch was not guarded at all.

Here it is on the Colt Model 601, the first production AR-15 model, of which approximately 14,500 were manufactured, mostly for military testing (project AGILE, SF/SEAL evaluation in Vietnam, etc.). This catch is identical to those seen on surviving prototypes.


One of the complaints from these early tests was that the exposed magazine release would occasionally lead to an uncommanded ejection of the mag while moving in thick brush.

The Model 602 (which is labeled “Model 02” on the left magwell) was purchased in about 19,000 units, primarily for Air Force base defense and plane/weapons guard purposes. It has the same arrangement of slabside receiver and mag release button. It was with full rate production of the M16 (USAF rifle,  Colt model 604) and XM16E1 (US Army rifle, Colt model 603) that another change to the receiver made it possible to guard or “fence” the magazine release.

The change was the substitution of a captive pivot pin, retained in the lower receiver by a spring-loaded detent running in a groove, much like the rear pin, called the “takedown pin,” had always been. A boss needed to be added to the lower receiver, to provide a race for this pin’s detent and spring to run in. Since the forging dies needed to be modified anyway, it was relatively trivial to extend the boss and make it a “fence” riding above the magazine release.  (This is the center receiver in the three-image picture below). Now, bumping into a stand of bamboo didn’t mean a lost mag any more.

Except, reports from the field indicated that it still did. As a result, the users — mostly the Army, based on Vietnam experience — asked that the rifle be modified, again. The request was brought to the Rifle Technical Committee on 13 Jan 66. It was feasible to change Drawing No. 62300 for the M16 and XM16E1 common lower receiver forging, as the running change log of Product Improvement Modifications records, “To respond to Army request to provide protective boss around the area of the magazine.” The Army contracting office approved the change on 16 May 66, and sometime relatively soon after that date the forging dies were modified to incorporate the “protective boss” which has since come to be known in the collector community as the “full fence.” A comparison of the three different receivers, showing the different forged outer right magwell side, is below, based on thumbnails at the Retro Black Rifle site (which also provided some of the other photos, although the AR-10 photos are from Julia Auctions and from the collection).

Left: prototype through Model 602. Center: Pre-March-66 603/604 (XM16E1/M16). Right: post-3/66 603/604 (XM16E1, from 68 M16A1/M16)

Left: prototype through Model 602. Center: Pre-March-66 603/604 (XM16E1/M16). Right: post-3/66 603/604 (XM16E1, from 68 M16A1/M16)

All the earlier forgings were used by Colt; those that were machined already seem to have been used until they ran out on military 603/604s, some were retained for toolroom prototypes and other factory uses, and slabsided, early model forgings with different machining (for a pivot screw instead of a pin) continued to be used on civilian-market semi-auto SP1 rifles for over 20 years.

The fenced mag release solved the problem. It is very rare (a freak occurrence, in fact) to have some stick or branch (or interaction with other gear or aircraft structure, etc.), drop your mag. And yet, there’s no difficulty reaching the mag release with your right index finger and dropping the mag free for a rapid reload. (At least, if you’re right-handed. Yeah, the ergonomics are significantly worse for a southpaw).

Why All this Ancient History Matters w/r/t this Rifle Accessory

The saga of the growing “fence” or boss on the receiver’s magazine well is the story of successive responses to a real problem, inadvertent and uncommanded actuation of the magazine release. You might say the military found that a protected switch was a “tactical” and “combat” necessary, and their users were actually, not Walter Mitty, tactical, and really, not in a practical-shooting-competition stage sense, in actual combat. And they decided a protruding magazine release was a A Bad Thing®. Enough, indeed, of A Bad Thing® that they spent the money not once, but twice, to redo the lower receiving forging to insulate the user against the consequences of a protruding button.

And here’s what the Tactical Combat (gag me!) Button looks like, installed, close-up (this nicely-done image is from 248Shooters’ review, we don’t know if they took it or it’s a factory shot):

ArmaSpec MR close-up

As they do note, it’s a well-made small unit, but by installing it, we not only have resurrected the inadvertent mag-drop failure mode, the one that was supposed to be laid to rest in March of ’66, but we’ve also introduced a new failure mode, in that foreign matter can potentially get stuck between the large pad of the TCB and the side of the receiver. In fact, the receiver boss/fence could actually help entrap a vine, stick or other junk right where it keeps you from pressing the mag release down.

This is apart from two of the cons noted by the 248Shooters reviewer, that the screws need to be Loctited, and that, “Like most extended mag releases it does fall pray [sic] to having a bit of wobble.” Against that, we dragged M16 series rifles through Arctic and Alpine conditions in places like Canada, Norway, all over northern New England, and some of the 20k peaks of the Andes, and the factory release is readily manipulated with gloves and even with mittens.

One reason we harp on this design history is that you have to know why the designers designed features into the platform before you go redesigning them, lest you bring back failure modes that engineers thought they banished fifty years ago.

Just like when you hot-rod a car, you may change characteristics that were designed into it for a reason, you need to think before you hot-rod a rifle. If you’ve ever had to drive an undercooled, over-cammed, 12:1 compression race car in traffic, with a did-you-do-your-squats-today clutch and square-cut gears, you know what we’re talking about.


This sort of post is the kind of technical information we most like providing. But the US Department of State has moved to require prior restraint — Censorship, with extremely expensive licensing subject to arbitrary terms — on firearms technical information, in a wild grab to stretch the International Trafficking in Arms Regulations far enough to snuff out freedom of speech. (We’ll have more to say about that soon, including suggestions for how you can help, but from now on until this monstrous and deviant interpretation of the law is put down like a rabid coyote, every technical post will incorporate a note on this subject).

Quick Kill — Useful Skill

The Quick Kill instinctive shooting method that was once taught in the US Army remains a  useful combat skill. It has been supplanted in the training world by improved sights and a focus on extremely rapid use of sights, but we believe it still has a place in the training and combat world.

It’s faster to show than to explain this skill. Unfortunately, there are few quick kill videos digitized at this point, and none fell readily to hand.

Quick Kill traces its roots to the “trick shooters” of the 20th Century, men like Ed McGivern who had so mastered firearms that they could pretty much hit anything with anything — fast. In the 1930s through the 1950s there were many articles on what was then called “point shooting” or “hip shooting,” driven in part by the stylized cowboy acts of the era. A technical/training book called Instinct Shooting by Mike Jennings appeared in 1959 and sold mostly out of ads in the back of gun culture magazines. Frank Connor, an author of many shooting and hunting articles, espoused similar techniques, as did “Lucky” McDaniel who brought the skill to the Army.

The Army initially called this Quick Fire, but in the second generation of the unofficial training document had progressed to calling it Quick Kill. This was not something that was just taught to Special Forces: it was part of infantry training for several years, as the peacetime training base of a large and slow-moving army reluctantly assumed a war footing during Vietnam.

There were three phases to Quick Kill, which was, during its brief life, normally the second phase of Basic Rifle Marksmanship training, after the trainees were taught to clear, disassemble, maintain, reassemble, and function-check the service rifle, but before they were taught such marksmanship fundamentals as sight picture, trigger control, and steady-hold factors. Those three phases were:

  1. Firing with an air rifle with no sights. This was a block of three hours of instruction. Initially these were just Daisy BB guns stripped of sights. Later, the Army’s own Training and Audiovisual Support Centers (one on every post, they made and supplied training aids) made one by glass-bedding a Daisy in an M14 stock.
    Quick Kill TASC

    US Army photo from the David Albert collection.

    Later still, a special Daisy that was mocked up to resemble an M16, but with the sights blanked off, was made. Any of these modified Daisys are extremely rare today. This one was sold by Rock Island Auctions in 2011:Rock Island Daisy Quick Kill rifleThere are at least a couple of variations of this air gun, which is not surprising, as they were locally made in individual TASCs. There were probably rudimentary plans, possibly just a single undimensioned sketch. One thing they have in common is lack of any actual sights.

    Quick Kill M16BB

    Photo from the David Albert collection.

  2. Firing with a service rifle with blanked-out sights. For the M14, a “training rib” was created that did this and provided a shotgun-like “sight picture” (although the rifle was held well below the sight line in this training).
  3. Firing with the service rifle, but not using the sights. Three distances were used: 15, 30 and 50 meters.

Yes, in the late 60s and early 70s, your basic grunt learned to hit stuff with his rifle, then he learned to use the sights. Heresy, today. But a look at old AARs shows that our guys generally won the meeting engagements with their conventionally-trained PAVN opponents, so it might just be heresy that works.

The whole program consumed one or two training days for a basic training company. After that, the troops would move on to aimed fire. Initial controlled studies showed that trainees who experienced Quick Kill performed better at marksmanship, even at longer ranges, than those who had not. Instinctively, that seems a paradoxical result. The scientists speculated that increased self-confidence may have been at work.

A later survey showed that, yes, Quick Kill-trained soldiers had greater confidence in themselves and their weapons than soldiers who had not had that training. In the absence of any other logical theory as to why Quick Kill training improves hit probability at 300 meters, the confidence factor has to be the tentative conclusion.

In 1969, the Army and George Washington University researchers conducted another study on Quick Kill training (one of many sponsored by the Army’s Human Resources Research Organization, HumRRO), to see if money and time could be saved. Some groups continued to have three hours of air rifle training before moving on to a real rifle; some had only an hour and a half (this was not deliberately part of the experimental design, but the schedule happened to short some trainees; the social scientists welcomed this “found data” and incorporated it in the study). For the study’s sake, some training companies had the phase in which an attached rib is used to encourage instinctive firing deleted, and others retained it. The test showed conclusively that the Army was getting training value out of the air rifle and rib training: the groups that had the full training shot better than the ones that got the bowdlerized version. On the other hand, the test showed that they could make some changes to target ranges and reduce the number of rounds fired in the live-fire block of instruction, without compromising marksmanship quality. The key was reducing them together: if you reduced the round count while taking out one of three target distances (they went with 20 and 50m), there was no effect on training quality; if you reduced the round count, but stayed with 15, 30 and 50m, performance declined.

Remarkably, all trainees in this experiment at Benning were still being trained, even at this late date, with the obsolete M14 rifle. (Of course, National Guard units were still armed with WWII era weapons like the M1 rifle and M1919A6 light machine gun).

Quick Kill suffered the fate of many other Army innovations of the 1950s and 1960s — it became tainted by association with the lost war in Vietnam, and the Army banished it from its collective memory.

From time to time, someone tries to “rehabilitate” Quick Kill, as we suppose we’re doing with this post. The thing is, it works. You can train to hit targets at combat ranges without sights, and we firmly believe you should. (Think you’re hot stuff? Put some tape over your sights and run a Dot Torture or three. Spend a whole training session on it — and tell us if you don’t get better at it). Of course, the Army’s safe, simple, cheap starting mode — an airgun — is a great way to begin practicing Quick Kill.

Some more formal ranges, especially indoor ranges, won’t let you try this. They have their reasons. Your first few rounds will go unexpectedly high or low, but you will be surprised how quickly you can get on “minute of man” from a low position (pistol held centered at about chin height, long gun tucked below the armpit) or even from the hip. As with any practical shooting practice, start low and close in (if backstop permits; don’t do this if you’re shooting up on an indoor range or with an unknown range fan). When you’re hitting at smell-his-halitosis distances, then move the target back.

This skill does not replace aimed fire, but it supplements it in a potentially lifesaving way.

The facts are: you can learn to shoot accurately at short to medium distances without sights, with a lot of ammo, and a lot of practice. (But less than you might think it would take). Those mid-20th-Century guys, whether they were actual warriors or matinee idols, who blazed away with Colt .45s or Thompsons from the hip, are not as entirely incompetent as today’s training wallahs seem to think they are. In fact, today’s trainers are as stylized in their own way as the Western movie gunfighters of the 1950s were in theirs.

Here are some sources of more information.

Jim Keating describes some of the history on a nearly unreadable (gray text on black background, circa 1990) website, and will sell you manuals or training. He learned QK as a ROTC cadet in the 1960s.

Here is the 1971 version of the instruction “Training Text” (a document with less weight than a fully-doctrinal field manual). We apologize for the poor scan, it’s what DTIC had. The document describes a systematic and deliberate system of drilling rapid-fire point shooting just like the service drills any other soldier skill.

TT 23-71-1-Principles-of-Quick-Kill.pdf

Here’s one of the 1969 studies. There are more to be found on NTIS and DTIC.

Olmstead-Jacobs HumRRO 14-69 Quick Kill.pdf

This website has more detail, developed by David Lambert. Some of the photographs used above appear to be from Mr Lambert’s collection and we have revised this post to give him credit:



Repairing a Broken Firing Pin

Ever broken a firing pin? If you’re like us, you have, and then you either ordered a firing pin replacement, or had a gunsmith make one, if there was no factory or used firing pin to be had. Or maybe you just hung the weapon back in its place, your equivalent of the “too hard” file on our desk. This excellent video from the American Gunsmithing Institute (yeah, those guys that want to sell you approximately a million videos for approximately a million dollars) has gunsmith Ken Brooks in show-and-tell mode as he restores a firing pin — in this case, for a Winchester Model 1894 .30-30, but the principles apply whether your broken firing pin is in a Luger or a Lewis gun1.

It was rather eye-opening to us that he applies no heat-treating to the finished part. The spring-steel stock he uses is already heat-treated, of course.

The most valuable information in his entire presentation (which we watched raptly from end to end) was his description of the specs for firing pin fit and protrusion, and his reduction of these to simple rules which work not only for low-pressure blackpowder-era cartridges like the .30-30, but also for high-pressure modern rounds.

Next was probably his warning of the necessity of washing off soldering flux. Fine and good to solder the new pin in place, but his description of what happens if you let your customer go tripping out the door of your shop

You can extrapolate from here to some common firing-pin related problems you may have encountered. Light strikes or no strikes? check protrusion. You could have a short tip, or a firing pin held back by corrosion.

On some frequently-broken firing pins, Ken’s techniques won’t apply, for example on the simple turned firing pins in Tokarev rifle and pistol designs.  (Both firing pins have a design weakness, in that they have a large cutout for a retaining pin. Coupled with wartime manufacture that short-cut deburring and polishing, they are very prone to breakage at the corners of that recess. A little bit of bench work is in order if your firing pin has sharp edges or other stress risers in this area). But those pins are relatively easy to make, if you have a lathe.

Yet it turns out that this kind of pin is, if not easy, quite straightforward to repair. Repairing an original part detracts less from a gun’s originality than replacing a part, which may be a factor

Hat tip, the NRA.


  1. Hmmm, we might have overstated that. We’re not sure there’s enough material in a Luger firing pin (which is mostly hollow) to replace the nose and meet Ken’s at-least-half-inside requirement. And a Lewis gun’s firing pin is part of the operating rod, and if it does break, may break where a soldered-spring-stock repair is not practical. Fortunately, it’s overengineered and seldom breaks.

Update, surprisingly related:

The NRA reports that the State Department is trying to ban the internet publication of technical information like this and other material hosted at this blog. This is not surprising from those Game of Thrones wannabees. We intend to carefully read the proposal (.pdf; the State Department wall of verbiage begins in the lower right corner), run it by our ITAR consultant in the day job, and react accordingly.

We guess: the gun-banners in striped pants at Foggy Bottom are not going to like our response.

Did The US Adopt the FG42 After All.. as the M4?

“Hognose,” you are thinking, “has lost his ever-lovin’ mind.” Unless you were long in the service, in which case you will substitute a stronger term for “ever-lovin’.” Because, after all, the low-production FG42, which had a great influence on US postwar weapons development, is miles from today’s modular M4, which developed from a completely different concept, the SCHV (Small Caliber High Velocity round) and the selective-fire assault rifle.



Let’s go back to one of the earliest versions of the US reaction to captured FG42s, written by T/5 (a wartime grade for technical specialists, called “technical corporal” and paid a hair better than a “mere” corporal) John E. Holmes of the Foreign Material Branch at Aberdeen Proving Ground on 8 June 44. According to Dugelby & Stevens, this was “the first American appreciation of the FG42 to appear in print… therefore a most noteworthy document.” After describing the general arrangement, production characteristics, handling and originality vs. derivation of various FG42 features (the example(s) Holmes had was/were the “E” type or first model FG with the stamped metal butt and pistol grip), he suggests that its advantages might be well considered in future US martial-arms design:

Advantages of Design

The combination of advantageous features included in the design of this weapon has made it a very interesting piece which should be studied with future weapons in view.

The following features are suggested:

a. The method of reducing required by using buffer spring sliding shoulder stock system.

b. Reduction of muzzle climb due to the action and stock design.

c. The method of loading empty or partially empty magazines with standard rifle clips, cutting down the number of necessary magazines which must be carried.

d. High line of sight prevents distortion of target due to heat waves.

e. Folding sights prevent damage as the weapon is carried by paratroopers, or when not in use.

f. Reversible bayonet.

g. Telescopic bayonet.1

Do you see what we mean? The only ones of these that are not present in the modern infantryman’s M4 are the spring-loaded shoulder stock (not necessary on the light-recoiling 5.56mm cartridge, perhaps), and the “reversible” spike bayonet. In point of fact, the US already tried that with rod bayonets on the Springfield rifles of 1880-1888 and 1903, which were extremely unpopular with troops (and ultimately, overthrown by President Theodore Roosevelt as “as poor an invention as I ever saw,” leading to the familiar M1905 knife bayonet of the World Wars).

So no, we never adopted the FG42. But over the years, we did adopt most of its impressive features. So did almost every major military in the world. And that is why the FG42,  despite having been produced in a quantity of only 8,494, maximum2, is, legitimately, considered one of the most influential weapons in history.


  1. Dugelby, Thomas B, and Stevens, R. Blake. Death From Above: The German FG42 Paratroop Rifle. New Expanded Edition. Coburg, Ontario: Collector Grade Publications, 2007. pp. 119-120.
  2. Ibid., p. 121.