Tag Archives: history

Whence Cometh PMAGs?

It occurred to me that there are plenty of folks who don’t understand how and why Magpul’s fantastic PMAGs became the standard magazine for AR-15 users both civilian and military. So let’s take a stroll down memory lane.

In terms of product, Magpul’s PMAGs1 hit a solid mix of reasonable price, reasonable quality, reasonable durability, and reasonable reliability of feeding (which is to say, function). They’re also pretty ubiquitous. Easy to find almost anywhere. While you can buy more durable magazines, they will cost you more. And mags that are cheaper by a large enough margin to care about don’t work as well.

Magpul wasn’t the first to come to market with a polymer magazine. Their first prototypes were made in 2006. They were among the first to come out with a polymer magazine that worked well, and they had built a customer base with some of their other quality products, like their magazine pulls (hence the company name).

Of course, the AR-15’s original magazines were made from thin aluminum. They were originally intended to be disposable after a single use, and this allowed the Armalite design team to make them very lightweight. However, the military did not go for that, and reissued magazines. Civilian shooters would also not treat aluminum magazines as disposable items either. However, the Armalite design team was not given a chance to redesign the magazines to make them more durable.

One of the things that will crop up with ‘USGI’ aluminum magazines is that the feed lips can deform, whether from being dropped or being smacked or whatever. And a property of metal is that when deformed with enough force, you’ll get “plastic deformation,” i.e. it will stay bent. If the feed lips get messed up, your mag isn’t going to work. These can be subtle problems. Your eye won’t know, but your rifle will. Like the princess and the pea.

Now, the military hates to throw things out, so mags that get bad from use and abuse (or stupid, stupid boots) are going to stick around. And civilians aren’t very likely to throw out bad mags either. They paid good money for those! That’s not to mention the affect of the 1994 Assault Weapons Ban, which allowed the sale to non-law enforcement civilians of standard capacity magazines made before 1994. So those aluminum mags were going nowhere. And those old mags were now worth a premium, so whatever crappy mag that a guy could dig up could be resold at a significant profit. Even if the mag was beat to hell.

I still have a folder of data on my hard drive of proper feed lip dimensions and instructions for retuning feed lips to get them close to original spec so that they wouldn’t induce double feeds. Ugh. Bad memories.

After the sunset of the ban in 2004, the market exploded with manufacturers making standard capacity magazines. Of course, the nature of the aluminum USGI magazines meant that it was pretty hard for the layman to tell if the magazine was made by anyone who knew what they were doing. Substandard materials or construction methods could lead to more problems. Or more rapid onset of problems. Or not; you could just get lucky.

Enter Magpul’s PMAG. Magpul hit the market with a good design, good materials (finally–remember this wasn’t the first attempt at a polymer AR-15 magazine), and good quality control. If you bought a Magpul PMAG, it would work, unlike previous polymer magazine efforts. And you didn’t find PMAGs in a box with a bunch of other curbstomped mags at a gunshow. Even if you did, they looked distinctive. Plus, they were cheap enough to buy a lot of.

Once they got the polymer magazines working well, Magpul’s choice of material brought other benefits. Polymer doesn’t deform like aluminum does; ironically it doesn’t do “plastic deformation”. It’ll either spring back to its original shape (elastic deformation) or break. And when it breaks it’s obvious. Maybe there’s a chunk of feedlip missing. Maybe there’s a big crack down the back of the magazine. Maybe the weld split. And it’s probably going to vomit bullets all over the floor when you try to fill it.

There you have it. Why we love our PMAGs.


  1. All caps, because Magpul spells it that way. And when I say PMAG, I do mean “Magpul’s PMAG” not something else. Not the imitators. And I like Magpul a lot, so I’ll happily oblige them on their branding. 

Resurrected Weapons: Project Babylon

Back in the 1950s, when rocketry was extraordinarily difficult, and TV was full of videos of NASA rocket tests failing miserably, Gerald Bull had an alternative idea: Use a giant gun to put a payload in orbit. This led to Project HARP, which got a lot of great research done. By the 1960s, we had figured out (mostly) how to make rockets that work. It was still hard, but now we could generally expect launches to work. And so the plug was pulled on HARP, but Gerald Bull still dreamed of using a giant gun to put a satellite in orbit. Eventually, in the 1980s, he found someone with money willing to back his dream once more. That man was Saddam Hussein.

Project Babylon came in two phases. Stage one was “Baby Babylon”, a proof of concept model with a 350mm bore and a barrel length of 46 meters. This was initially used for horizontal testing, and was then erected on the side of a mountain. The full size “Big Babylon” would have been the biggest gun ever, with a one-meter bore and a barrel length of 156 meters. The original design was intended to be suspended from a steel framework by a system of cables.

Testing of the Baby Babylon cannon showed issues in dealing with seals between the barrel sections. While these were being fixed, Gerald Bull was assassinated outside of his Belgian apartment on March 22, 1990, which crippled the project. It would not be resumed after the First Gulf War.

Bull’s assassination was almost certainly not due to his work on Project Babylon. The superguns were massive, fixed targets. Easy to spot with aerial or satellite reconnaissance, easy to destroy. But Bull was also working on improving the range of Saddam’s Scud missiles. Those are much more effective than a giant gun. This was the project that most likely angered Saddam’s enemies enough to get an assassination. The most likely candidates are Israel or Iran, both of whom have intelligence agencies with lots of experience in liquidating potential problems.

Project Babylon itself is also extremely problematic. It’s a lousy weapon, as we’ve mentioned before. But I’m also extremely skeptical of their utility as a launch system. Even with a 156 meter barrel, the acceleration is going to be absolutely brutal. This is going to seriously restrict the payloads you can launch. A rocket is going to be far gentler on the payload, and much less likely to wreck a satellite. Plus, rockets can accept oversize shrouds to handle larger payloads, or be clustered to lift more weight. You’re pretty stuck with the weight capacity and payload diameter restriction here.

Verdict: Funding Request Denied by the Borgundy Ordnance Board

There Is No Milspec AR-10

Anytime I hear the words “milspec AR-10” my teeth get set on edge. There’s no such thing. I’m gonna repeat that.

There is no such thing as a “milspec AR-10”.

Got it? It should be pretty clear. No. Such. Thing.

Let’s start with what exactly is “milspec.” You may have guessed it’s short for “military specification,” and you’d be correct. For the US Army (and some others), they like to take ownership of certain products. Sometimes there are competitive bids. For the M4, there’s a specification of what exactly an M4 is, and then the US Army can have companies bid on how much it will cost to make a certain number of rifles to that spec. The milspec is owned by the military (in general).

So there’s no “milspec AR-10” because no major military adopted the AR-10 and cemented the design that way. Emphasis on the and. Merely adopting the rifle is insufficient. The AR-10 was used by the Sudanese, Cubans, and the Portugese, but none of those made a spec. All of those arms were built by Artillerie Inrichtigen, which wasn’t able to get more contracts and stopped making AR-10s ages ago. Still no spec.

Things got confusing in the 1990s. By that time, Eugene Stoner was working for Knights Armament, and they made the SR-25, a modern take on the AR-10 design for use as a semiautomatic marksman’s rifle. This used the gas system improvements worked out on the AR-15 and had a number of parts shared with the then-issue M16A2. The magazine design is also used in DPMS’ AR-10-pattern rifles, among others, and you can find these magazines as “DPMS/SR-25” pattern.

There’s another pattern of magazines currently in use for AR-10-pattern rifles. This one is made, confusingly enough, by Armalite. The original Armalite company ceased operations in the early 1980s. The rights to the name were bought, and Armalite was relaunched in 1996, with a new AR-10 pattern rifle (among other things). At that time the 1994 Assault Weapons Ban was in effect in the United States. This bill prohibited the sale of new magazines with a capacity of more than 10 rounds, but older magazines that held more than 10 rounds could still be bought and sold. So (new) Armalite made magazines that had a common design with M-14 magazines, so buyers of their rifle could use existing, common M-14 magazines with a couple easy modifications. These are “Armalite” pattern magazines, and they’re not compatible with DPMS/SR-25 pattern magazines.

And no, neither DPMS nor Knights nor Armalite are responsible for any current milspec “AR-10-pattern” rifle.

Competition Meets Tactical: SOF STI 2011s

I love competition shooting, and I love modern military gear. Sometimes, the two worlds collide, and I always find such events fascinating. Let’s take a look at a little bit of Special Operations history, courtesy of an old Gunbroker auction and the late, great Weaponsman.

First, some competition background. In the USPSA Limited1 division, the dominant platform is the double-stack 1911, often called a 2011, which is the trade name used by STI for their pistols. Since STI is the biggest builder of these, and where to go for a factory-type solution, the name has stuck. While people use other guns in Limited, the 2011s are the most popular. Since it’s based on the 1911, with its expired patents, its wide open for people to play with, so you can get your gun customized to your heart’s content. While it’s the indian, not the arrow, that decides results, nobody wants to shoot a lame arrow. Plus the 1911-style, single-action, sliding trigger is super easy to make amazing. There are no better triggers than a tuned 1911-type trigger for shooting.

Around 2006-2007, one of America’s elite special operations units decided to experiment with these pistols. Here are a pair of them.
STI 40s

A few things to note. They’re chambered for .40 S&W, not 9mm NATO like you might expect. Being based on the 1911, which was originally designed around the .45 ACP cartridge, 2011s tend to be easier to make reliable with longer cartridges. .40 S&W is a bit longer than 9mm NATO, so that helps. Plus, the vast majority of 2011s are chambered in .40 for USPSA,2 that’s where most of the experience in keeping them running is focused.

From the auction description:

Both of these STI 2011 .40 caliber pistols saw actual issue and use in a US Army SOF unit in 2006-2007. One pistol is in 93%+ condition and the other is in 96%+ condition. They are consecutively serial numbered and are quite possibly the only consecutively numbered set to be offered for sale. This consecutively numbered set comes with the following items: *** individual letters of authenticity from Larry Vickers (www.vickerstactical.com) for each pistol— original, unedited versions will be provided to the buyer *** six 140mm 17 round magazines *** one 170mm 22 round magazine *** one issued Surefire X200A light *** issued Safariland 6005 light bearing holster with end user modifications *** two Eagle Industries pistol cases

These are standard STI magazines with STI follower and basepad. This doesn’t sound odd, but most competitors will swap the follower and basepad out to get more capacity. More capacity is great at a match, but it tends to make the mags a bit more fussy, and extra maintenance requirements are not the friend of the combat soldier.

What did SOF think of these pistols? They liked them, but found the maintenance requirements to be more than they wanted to deal with. Specifically, issues came up with fine desert sand from the Middle East. This makes some sense. These are tightly tuned competition pistols, built for maximum shootability. Competitors don’t mind having to do a bit more cleaning of their magazines. And of course, as a general rule, guns with a metal frame and slide need more lubrication than those with a polymer frame and steel slide.

That said, in Vickers’ letter of authenticity, he said that “these were the only pistols sold outside the unit” (emphasis added). So likely lots of the men chose to keep the pistols, because they are awesome and shoot really well. Even if they might not be the best choice for a secondary weapon out in the sandbox.


  1. No electronic sights, no compensators, no barrel porting, magazines no longer than 141.25 mm. 
  2. Because power factor. 

M1 CATTB

The Component Advanced Technology Test Bed was another late 80s American test program to investigate new systems for future tanks. As we’ll see, it looked quite a bit different from the TTB, and where the TTB was testing a very specific change (namely the unmanned, low profile turret) the CATTB tested a variety of new technologies in a more conventional layout.

CATTB

CATTB shared an Abrams hull, but the turret was new, and came with a bustle-mounted autoloader. The autoloader was very similar to the one on the Leclerc or K2. A new gun was tested, the XM291, which came in both 120 mm and 140 mm versions. The 120 mm version provided a lower-risk alternative to the 140 mm. The turret had rather large forward armor arrays, plus reasonably thick side arrays and a decent amount of roof protection. And I have no idea why they decided to mount so many smoke grenade launchers on there, but they did. This was before the advent of soft-kill active protection systems, but might not go amiss on a tank today with the right cueing system.

CATTB Rear view

As you can see from this rear view, the CATTB also came with a new engine: the XAP-1000 diesel. The Cummins/Allison XAP-1000 was based on the advanced Cummins XAV-28 V-12 diesel, a low-heat rejection engine. It used only oil coolant and has no water in the cooling system at all. Higher temperature exhaust gasses were tapped to run the APU. I don’t know a ton about this engine, but the US Army has a history of backing highly advanced diesel engines that end up being problematic. I would suspect similar things with the XAP-1000. Again, the project went nowhere. Later in the 90s, the Abrams was going to get a new engine as an offshoot of the Crusader project, but the proposed engine was not the XAP-1000. Instead, a gas turbine was chosen.

CATTB is a lot more of a conventionally designed tank. I do really like its lines. The project which was supposed to lead to the Block III MBT ended up leading nowhere due to changing priorities. Though, it is not at a museum. It is in the long term storage section of the Sierra Army Depot in Hurlong, CA. Make of that what you wish.

On the 140mm Tank Gun

Let’s talk some more about the 140 mm tank gun, that late cold war weapon that never was. Perfect for killing Soviet Supertanks that never were. And making your new tank way cooler than everyone else’s. The fastest way to get more armor penetration is to just build a bigger gun with more muzzle energy. A lot more.

As you might imagine, a 140 mm round is quite a bit bigger than a 120mm round. Let’s take a look, because these numbers are damned hard to find:

First, a typical 120 mm APFSDS round for the era, the American M829A1. The legendary Silver Bullet that slaughtered the tanks of Saddam’s Republican Guard. Some variations in length and weight are to be expected amongst 120 mm rounds. Newer rounds are a little heavier, but the size is constrained by ammunition storage racks and the existing chambers. The M829A1 is also the round that was in service while the 140 mm was under development.

M829A1 120 mm APFSDS
* Length: 984 mm
* Weight: 20.9 kg (46 lbs)

And now, the round to replace it. Producing 23 MJ at the muzzle, more than double that of the 120mm. The mighty 140. Dimensions were fixed by the NATO countries that were all developing their own versions of the round.

140mm tank round

XM962 140 mm APFSDS
* Length: 1,482 mm
* Weight: approximately 40 kg (88 lbs)

The length and weight of the 140 mm stand out. This round would have been a royal pain to handle. It’s also a bit fatter, so autoloaders could handle fewer rounds. This explains why the K2 Black Panther, otherwise similar to the Leclerc, can only hold 17 rounds in its autoloader compared to 22 in the Leclerc. The K2 is ready for 140 mm, needing only a barrel change. Interestingly, the round count in the Black Panther matches those for the M1-CATTB prototype, which had a similar, belt-style autoloader in its bustle. Don’t worry, we’ll talk about the CATTB in a future article.

NATO-standard 120 mm rounds like the M829A1 are unitary rounds. One big piece, like an oversized version of the cartridges you load into your guns at home. Because of the large size of the 140 mm rounds, these were made as two-piece rounds. Unfortunately, while I can find dimensions for the round’s overall length, I don’t have dimensions for the pieces. Until I can find one to measure myself, we’ll have to make do with some pixel counting/scaling, which yields a length of about 1,024 mm for the upper part of the round, and about 461 mm for the lower part. Which is still big and annoying for autoloader development. Length of the upper part of the round is heavily influenced by the length of the APFSDS projectile. This also would affect a design using a carousel autoloader like the TTB, since carousel (and therefore hull) height and turret height are constrained by the requirement to lift and rotate the rounds into position.

Based on the standards of the day, the 140 mm gun made more than twice the energy of the 120 mm at the muzzle. Of those 23 MJ of muzzle energy in the 140 mm, 14 MJ goes to the penetrator. Running the numbers meant that the 140 mm APFSDS could punch through more than 1,000 mm of RHAe at a ‘battle range’ of 2 km. For comparison, we’ll pull some open source estimates for M829A1, which give it a penetration of 700 mm of RHAe1.

Now, those are some really good numbers2. Of course, there’s a price to be paid. Even with the two-piece construction, everyone working with the 140 mm designed with autoloaders. Which meant significantly reworked turrets for the British, the Germans, and the Americans at a minimum. Plus, ammunition capacity would drop.

Upgunning to a 140 mm round was the simplest way to get a lot more armor penetration capability into a tank. At least from a weapon/projectile design standpoint. It would have required some serious reworking of then-extant designs, but such is life. When the Soviet Union imploded, the armored threat of the projected Future Soviet (super)tanks evaporated, and the 140 mm gun projects were quietly shelved. 120 mm rounds are continuing to get more development and the latest are quite a bit more effective than the M829A1. Lower cost, likely lower capabilities, but this decision makes sense given the circumstances.


  1. There’s some variation in this estimation depending on source. Open source disclaimers apply, etc. 
  2. They’re also a trifle disingenuous. Nobody is armoring their tanks with a meter of rolled homogenous steel. Literally nobody. A more advanced penetrator design can exploit effects on the not-steel that people actually armor their tanks with. Similarly, the armor might be designed to radically degrade (read: break up) the penetrator, which can be sort of but not really captured in RHAe estimations. So the RHAe numbers don’t actually tell the whole story on either side of the design puzzle. Oh, and the numbers themselves are the usual open-source estimates3, so they’re probably all wrong. 
  3. If you’d like to try your hand, start running through the Odermatt equation. And then remember that Odermatt wrote for tungsten-based penetrators, and M829A1 is depleted uranium, so you’ll need to tweak it. 

M1 TTB

The M1 Tank Test Bed (TTB) was a late-80s prototype to test unmanned turret design concepts and compare them to a modern, manned-turret design: the then-state-of-the-art M1A1. The TTB was not necessarily intended to be what the next MBT would look like, but it was intended to shake out some design concepts and see if they were worth considering in the future. So let’s take a look.

m1 ttb

Some of you may notice a resemblance to the T-14. Both use similar unmanned turret design concepts. Such designs have been kicked around since the 1950s by many different groups of tank designers, and all for similar reasons of being able to reduce protected volume (and hence reduce design weight for a given standard of protection). The M1A1 weighs about 57 tonnes. The TTB, with a similar protective standard and the same 120mm gun (and a similar ammunition capacity) was reckoned to weigh about 15% less, for an approximate TTB weight of 48.45 tonnes. Interestingly, this is very close to the published weight for the T-14.

TTB also, of course, reduced crew to three men and put in an autoloader for ammunition handling. The design was intended to improve crew safety by completely isolating the crew from the ammunition. The autoloader itself was a large carousel, holding all ammunition below the turret ring. Let’s look at some pictures.

ttb autoloader

It’s sort of like the autoloader on the T-80, though NATO 120mm ammunition is one-piece, and is therefore a little more annoying to design an autoloader for. The autoloader built for the TTB held 44 rounds and this could be expanded to 48 or even 60 rounds with minor design changes. All of the ammo was stored in a ready configuration because the crew would be unable to move ammunition from a reserve magazine to the autoloader’s ready magazine (as on the Leclerc for example). The TTB autoloader was extensively tested, and could manage a rate of fire of one round every 12 seconds. Spent case bases or misfired rounds were ejected out a small hatch the back. The autoloader could be supplied through the rear hatch, and also had an unloading mode where it could slowly present rounds for removal. The autoloader weighed about 1,400 lbs. empty.

Some might question the vulnerability of such a design. However, statistically the vast majority of tank hits occur to the turret. Tanks like the T-72, for example, ran into trouble because of the ignition of their unprotected reserve ammunition stowage in the turret, not hits that set off ammunition in their autoloaders. And again, complete isolation from the ammunition should keep the crew relatively safe.

The TTB program was dialed back with the end of the cold war and was finally cancelled in the mid 90s. The autoloader design was used in the M1128 Mobile Gun System version of the Stryker.

As for the TTB prototype, it’s at the National Armor and Cavalry Museum at Fort Benning, and has recently been restored and repainted.

Night Vision Equipment

History is a great thing to learn from. And one of the details that we can look to history for lessons on is the basis of issue: how many of what things a given unit should have. This is often hard to work out without any kind of experience, so let’s look to some troops with experience. The following is based off of notes from Marines in Iraq circa 2003 or so and the related Marine Gunner’s Conference, so some of the equipment may be a little out of date. I’ve noted alternatives where applicable. These marines saw combat and used their equipment heavily. The overall base unit here is a rifle company (182 men), so the numbers for items will be referenced on that basis.

PVS-14 (Night Vision Monocular): These should be issued one per man (182). Monoculars are liked because they allow one eye to remain open for peripheral vision or shooting if another optic is mounted on the weapon. PVS-14s are Gen 3 light amplification devices and are still pretty good. There are alternatives that integrate thermal at present. One other thing noted in the report: helmet mounts are required. The strap mounts aren’t very good, and don’t work well with helmets.

3X Magnifier: None of these were listed on the table, and our veterans differed a little. The 3X magnifier is a useful observational tool, especially in the desert. The panel recommended at least enough magnifiers for stationary gunners and forward observers (40), if not enough to also equip the fire team leaders (67). A handheld magnifier is useful for observing without necessarily orienting one’s weapon toward the target. Note that there are also 6X magnifiers available at present.

PEQ-2 (IR Laser sight): The PEQ-2 is a laser sight to aid in aiming with night vision devices. The findings were that every weapon that could mount a PEQ-2 (i.e. basically everything that wasn’t a pistol) needed a PEQ-2, which works out to 176 units. The PEQ-2 is heavy and bulky. It is outmoded, if not obsolete. Much better choices exist today, including the DBAL, ATPIAL, and the MAWL. The MAWL is best of breed as I write this.

VLI (Visible Light, i.e. flashlight): The standard flashlight, capable of being used in the hand or being mounted on a weapon. The findings were that every rifle needed a light, especially for urban operations. This works out to 134 lights. Additionally, the marines agreed that the VLI itself was too big, too heavy, and needed too many batteries. They requested a smaller, lighter flashlight. The Surefire M600 Scout Light comes to mind as an excellent long gun weaponlight choice today.

If you’re curious about IR illumination for use with night vision devices, there are variants of the M600 (and other flashlights) that can output infrared in addition to white light. Also, many laser sighting units come with a built-in IR illuminator.

PVS-17B (Night Vision Weaponsight): The PVS-17B is a dedicated night vision weaponsight, complete with reticle and 2.5X magnification. This was found to work well on support weapons, including the M-249, AT4, and SMAW. This works out to 39 PVS-17Bs. It was not favored on rifles, because a PVS-14 could be mounted in front of the RCO, giving similar capability for less weight and hassle. The PVS-17B is pretty heavy and bulky. These days, the PVS-22 is often preferred. The PVS-22 is designed to give night vision capability to an existing optical sight rather than replace it like the PVS-17B. However, given that the PVS-17B is also a 3rd Generation light amplification unit, it’s not outmoded.

PAS-13 (Thermal Weapons Sight): The PAS-13 is a thermal imaging weapon sight. The original model was quite heavy and bulky. It was favored by the committee only for machine guns (M-249 and M-240 gunners), which works out to 33 units. The committee did suggest that machine gunners carry both PAS-13 and PVS-17B sights. Since Operation Iraqi Freedom, newer versions of the PAS-13 that are significantly lighter and less bulky have come out. The PAS-13G is even reasonably sized to mount on a rifle.

RCO (ACOG): The Marines RCO of choice is the ACOG. They favor the TA31F, which has the red chevron reticle with fiber optic and tritium illumination and fixed 4X magnification. Marines love ACOGs, and the Gunner’s Committee was no exception. The magnification is very useful for target acquisition, identification, and discrimination. They sought one per rifle, or 134 ACOGs for the company.

IR Beacons: This is a little blinking IR light used for identification. While none were on the allocation table at the start of Operation Iraqi Freedom, they are very useful for helping identify friendly units and avoid blue-on-blue incidents. The committee figured every fire team and every platoon sergeant should have an IR beacon, which comes to 5 per platoon, or 25 per company.

Laser Boresight System: Not a combat weapon, this is used for boresighting. Duh. It is also useful for boresighting the aforementioned night sights and rocket-type weapons like the SMAW or AT4. Every squad needs to be able to boresight its stuff. They figured 20 boresighters per company would work well.

PEQ-4: This is a powerful IR laser pointer. For pointing while using night sights. It’s powerful and can be distinguished from the PEQ-2 lasers. PEQ-2s aren’t really able to be seen well by vehicles or aircraft if they’re not right on top of the user. The committee recommended 10 per company for platoon leaders, company leaders, and machine gun leaders. The aforementioned laser sights that have replaced the PEQ-2 are also a lot more powerful, and have obviated the need for these.

M-24 Mini Binoculars: Not night vision equipment. These have 7x magnification. Despite having ACOGs on their weapons, squad and team leaders found binoculars to be very flexible and useful. The committee recommended 27 per company.

The committee also realized that the above recommendations are not without their own issues. These devices add quite a bit of weight to the Marine’s rifle. These devices have their own switchology that requires training, require batteries (other than the RCO–ACOGs don’t need batteries), and add maintenance requirements.