The Last Battle Of The Musket: Making The Never-Happened M16A5

When the Marine Corps began changing out their old M16A2 rifles for the newer M16A4s after the beginning of the Iraqi War, there was an internal contingent pushing for the compact M4. 

The M4 carbine not only has a shorter 14.7-inch barrel than those 20-inch Marine Corps muskets, but importantly, it features a collapsible stock. In fact, the major complaint about the M16A4 from those actually fighting on the ground wasn’t the barrel length but that lack of an adjustable stock. 

The longer fixed A2 stock combined with body armor and paired with an optic with an extremely short eye relief made everything harder. Not impossible, but needlessly difficult in the way the Marine Corps perpetually likes. 

When the rest of the world moved on first with the M4 and then with the improved M4A1, the Marine Corps continued to go full-bore with the A4. The official line is that the Marine Corps wanted to keep the better terminal performance provided by the longer barrels.

It’s true that longer barrels make antiquated ammunition designs like SS109/M855 perform better ballistically, but modern ammunition closes that gap. It’s also true that the old traditionalists at the top clutched pearls and decried that the pomp and polish of coordinated rifle drill couldn’t be readily performed with the shorter rifle. 

Something to keep in mind is that the Marine Corps isn’t always a rational actor; a place where parade and mythology hold as much weight as actual efficacy can come off as clinically obdurate. 

The idiom of generals always fighting the last war isn’t only historically true, it also applies to wars inside the organization itself. While fights can come from anywhere, they’re especially prevalent surrounding the development and procurement of new vehicles and weapons. The M16A5 was one such little war. 

The M16A5 concept was a way to add that adjustable stock but keep the generals who think we’re fighting in trenches happy with a 20-inch barrel. It would’ve been a natural progression, but the real swan song for the M16A4 came in the form of the much more versatile M27 Infantry Automatic Rifle (IAR). 

EARLY ATTEMPTS

While all sorts of buttstock/barrel/gas system combinations have been plastered together by individuals, Canada was the first to pair an adjustable stock with a musket-length barrel at an organizational level with the C7A2. (This wouldn’t be the first time the Marine Corps copied some Canadian homework; their MARPAT camouflage is based on CADPAT, after all.)

In the early/mid aughts, some armorers in Marine Corps Force Recon units were marrying adjustable stocks from M4 rifles to the longer-barreled A4 systems. 

Though these days there are a lot of known quantities, for most of its existence the AR has been a modify-as-needed system — with engineering challenges to overcome along the way. The entire AR/M16 platform is like an algebra equation: everything is A-OK so long as each end balances out. The gas system, barrel length, and action have to work well together. You can’t always just swap out parts and have it rock ’n’ roll. 

Ultimately, this takes more nuance than simply stock and spring swapping, at least if you want it to work. Many of those guns became ammunition-sensitive or suffered from problems like bolt bounce during automatic fire. So, a call went out …

THE A5 SYSTEM

Answering the call was VLTOR Weapon Systems, an Arizona developer known for their fresh approaches and conscientious engineering. It was an adjustable stock system that was more than a mere M4 stock. It was named the A5, because presumably that would be the designation of the coveted M16A4s that were converted.

Everything about the VLTOR A5 is intermediate, bridging the gap between the world of an M4 and an A4. The receiver extension tube is longer and has seven positions instead of six; when fully collapsed the A5 has a length of pull of 11.5 inches, which is about an inch longer than the M4 at the same. 

Fully extended it’s 16.25 inches — significantly longer than the old fixed A2/A4.

The buffer is similar story, longer than the carbine, shorter than the rifle, but maintaining rifle weight. 

The recoil spring is exactly the same as the A2/A4 rifle, but stuffed inside that smaller seven-position tube. This doesn’t mean that the spring is more compressed when used, quite the contrary: the correspondingly shorter buffer accommodates the recoil stroke perfectly. 

Though any Mil-spec buttstock will fit on the VLTOR receiver extension, the standard is the EMOD, Enhanced Modular stock. The EMOD is as adjustable as you’d expect with a lot of on-board storage for batteries and other small parts.

You end up with a smooth, reliable system with increased parts longevity compared to the M4 and even the old A2 — Marine Corps testing proved that out over thousands of rounds (the results of this 2010 publishing were online for under an hour prior to being pulled).

SO, WHY NOT?

This whole A5 experiment happened during a pivotal transitional time for the Marine Corps. The Iraq War was winding down, eyes moving east once again toward Afghanistan. 

Improved barrier-blind ammunition was adopted, negating the barrel length ballistic arguments. VLTOR and the M16A5 ultimately didn’t make the cut not due to design or reliability issues, but because of the M4 and M27 advocates correctly deducing that the VLTOR A5 system would lengthen the lifespan of a rifle they wanted away with anyway. 

The idea of a collapsible stock on a musket lived on in the Army. The M16 Hybrid Buttstock conversion was born, and it consists of a standard carbine stock system but with a bespoke recoil buffer named the H6. Curiously, the Army comics about this conversion first featured a Magpul UBR stock instead of an M4 stock, but only the M4 stocks shipped out. 

Overall, the standard M4 carbine tubes, stocks, and springs beat out the VLTOR A5 system. It wasn’t because M4 stocks were more effective (both systems worked within parameters) but more administrative. One of the reasons the United States has the best military logistics in the world is because the U.S. Military pays attention to logistics. All that’s needed for the M16 Hybrid Buttstock conversion is the new H6 buffer, the rest being the same already-in-system inventory. Whereas with the VLTOR A5, the only already-official item was the action spring. 

The M16A5 would’ve absolutely been an improvement on the M16A4 in terms of individual handling, but also would’ve been just another Band-Aid before simply getting M4s or IARs like the people on the ground wanted in the first place. Let the ol’ generals keep their muskets, and then slip the M27 IAR through the hole of a precision rifle and automatic rifle roles before simply implementing everywhere. 

DOING IT YOURSELF

All you really need to do for a clone is take a Marine Corps M16A4 and add a VLTOR A5 stock/combo kit. So, we did that and it looks right, but it was boring and this isn’t a clone, not really — this is a gun that never existed. The concept of a plan. While you can colloquially call any rifle-length gas upper paired with a collapsible stock carbine lower an “A5,” here we tried to remain within the confines of the illogical logic of the Marine Corps. It must be plausible in form if not in actual reality; items can be contemporary and from anywhere.  

The base requirements for our M16A5 build:

• Genuine A5 stock system
• 20-inch 5.56mm barrel with A-frame sight
• Quad rail handguard 
• Bayonet compatible 

Of peak importance is a genuine A5 stock system, not something pieced together. Step number one is obtaining a VLTOR AEBK-A5 combination kit. Because if it weren’t for VLTOR and the subsequent testing, we’d be calling these C7s and not A5s.

The Aero Precision M16A4 Clone Complete Lower paired with one of their 20-inch A-framed 5.56mm uppers would be the base. We went with an Armaspec Victory charging handle because it’s truly ambidextrous and vents suppressor gas well. We successfully resisted the urge to swap the A2 pistol grip, but the rubbin’ nubbin’ was sanded off. A TriggerTech Duty Trigger was installed in lieu of the Mil-spec OEM for the sake of our trigger finger. 

Though the A4 would normally feature a Knights Armament or P&S rail, here a rifle-length Midwest Industries Combat Rail T-series serves as the handguard. Originally, the idea was to use a longer model and cut out a hole for the A-frame, but that would’ve required taking off the bayonet lug. 

The Marine Corps famously wants the ability to put a bayonet on everything, so that option was a no-go. A further kowtow to the bayo was that the A2 flash hider remained, though the crush washer was replaced with a peel washer to increase silencer compatibility. 

In actuality, the rear sight you’d most likely see on an A5 is a Knight’s Armament folding micro, but in the spirit of ridiculous, there’s an option for a full carry handle mounted to the rail like the earliest M16A4s. In that same flavor, there’s a B+T Unigrip (aka “chow hall kickstand”) installed. The weapon-mounted light is still a SureFire, but an updated Scout Light Pro. 

For an optic, an ACOG is the most obvious answer, or alternatively the VCOG that the Marine Corps is also now issuing. The Primary Arms SLx with ACSS reticle wouldn’t exist without the ACOG and is spiritually similar without being the same. 

Because there was a rail on top, we attached a micro dot sight; the Crimson Trace Rad Micro was the first we plucked from the pile. It’s also kind of fun to have the vertical grip or the flashlight cost more than the optic itself. Also pictured is the excellent EOTech VUDU 1-8x optic — the first optic is kinda trolling, but the EOTech is for rolling. 

Build List:

IN USE

No bones about it, the M16A5 isn’t exactly a handy rifle but the adjustable stock makes it a bit more bearable — especially if you’re sharing a rifle at the range. It still shoots and balances like a full-size rifle but it’s more easily accommodating to a bevy of different bodies. Though ballistically a 20-inch barrel isn’t that much better than a 16.5 (score another point for the M27 IAR), it does have an edge over the M4 carbine’s 14.7 incher.  

The VLTOR stock makes adding and removing a sling much easier than the parade stock attachments of the M16A4. The EMOD — with its on-board storage, ambidextrous QD sling sockets, and durable construction — is an improvement over both the fixed A2 and M4 stock with one large exception: the beard-grabbing design along the comb. 

This isn’t really an issue with conventional forces in garrison but was quite a literal pain for special units. Solutions ranged from something as simple as a piece of 100 MPH tape across the top to filling it all in with adhesive. Had it not been for the beard buster, the EMOD might well be wearing the same buttstock mantle as the SOPMOD. 

The rest is all bog-standard M16 stuff. It would’ve been nice to have it 20 years ago, but the time for the serious use of this system has now passed. 

LOOSE ROUNDS

These days it’s hard to imagine urban fighting with a gun as long and cumbersome indoors like the M16A4, yet we’ve done exactly that in the past. You can make the same argument about the M14, M1 Garand, and the M1903. Just because something isn’t perfect doesn’t mean it’s unusable, but let’s not pretend just because something is usable it’s ideal.  

Even though the M16A5 was never officially adopted, the A5 stock lives on not only in the civilian market but in the form of AR-10 carbine stock tubes. Which is appropriate, because ultimately the A5 isn’t dissimilar to putting an adjustable stock on a 7.62/AR-10. There are a lot of combinations that can be reliable, if you’re willing to put in the work. 

Or just hit the easy button and do what we did here: Get the A5 Stock Combo Kit directly from VLTOR. 

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