I want to be clear, there was never an official designation of the M16A5 rifle. The image in the cover of this very article is actually the Canadian C7A2. As much as I appreciate the design we’re talking about today, the M16A5 isn’t a rifle for clone dorks to obsess over.
The US Marine Corps discussed the M16A5 concept circa 2013, and VLTOR put their version of it on display for a short time. But nothing came of it.
The Marine Corps ultimately decided to field the M4 carbine across the service in 2015, and later the M27 IAR, killing any hope of the M16A5 actually coming to fruition.
Today, the “M16A5” is less about the proposed concept and instead colloquially describes any combination of 20” rifle barrel and collapsible stock.
So why do I feel compelled to write this article?
Just because the Marines chose not to field it doesn’t mean that the concept was invalid. In fact, the collapsible stock on a full-length upper is pretty common around the world. With this article, I’d like to walk you through some of the examples out there and share some pointers on building your own.
In the end, this configuration is extremely shootable. It’s one of my favorite rifles in the safe and works very well for a variety of tasks. To prove the point, it’s the one I chose to use in the NRA America’s Rifle match where I performed pretty well and was more hindered by my own lack of practice than the rifle itself.
History of the M16A5
Let’s talk about origins. The Marines were far from the first to toy with the concept of putting a collapsible stock on a full-length M16.
It wasn’t long into the fighting of Afghanistan and Iraq in the early 2000s before warfighters realized that a full-length rifle was less than ideal for urban fighting or riding around in vehicles.
You see, the M16 came about in an era of dismounted foot patrolling in expansive outdoor terrain. The troops wanted something more suited to their needs than the classic M16A2 and M16A4.
There also weren’t enough M4 carbines to go around.
During the same period, the Canadians ran into the same conundrum with their C7A1 rifles.
By around 2011, both armies came up with a solution. However, they approached it in different ways.
The US Army AAL M-16 Hybrid Buttstock Kit
By 2009, many individual soldiers were unofficially experimenting with the collapsible buttstock configuration. United States Army Tank-automotive and Armaments Command (TACOM) started fielding requests for proposals to make it official. They created NSN 1005-01-569-6938 in 2008 for the project, but never officially announced it as an approved accessory until 2011.
TACOM authorized the hybrid buttock for any M16A2 or M16A4 in service. The Army apparently ran it through a 200,000-round torture test before approving it.
The actual details are still locked behind approved access at dtic.mil, though.
The kit contained a standard M4 buffer tube, M4 stock, carbine spring, and specially-weighted “H6” buffer. Army units could purchase the kit for about $100 apiece for installation on their own rifles.
The hybrid buttstock kit still required an armorer to install it. Furthermore, it was considered a temporary modification and any rifle with it had to be returned to its standard full-length configuration before returning to the armory at the end of a rotation.
The June 2011 edition of the Army’s PS Magazine, #703, announced the change. If you aren’t familiar with it, PS Magazine is the Army’s monthly publication about periodic maintenance practices. It’s loaded with good information.
The image in the announcement, found on page 24 and seen above, looks suspiciously like a Magpul UBR. Don’t be fooled, though, the kit came with the standard M4 stock.
In a later edition, #771 from February 2017, a weapons inspector wrote the editor reminding readers that the stock from the hybrid buttstock kit was not interchangeable with the standard M4 buttstock. However, interestingly, the authors of the magazine “misinterpreted” the letter and instead talked about the buffers not being the same.
If I was to guess, the “inspector” wasn’t really a gun guy and was only looking at the stamp on the buffer to decide whether the whole stock was correct. Confusingly, though, the associated image once again depicted a stock that looks like the Magpul UBR.
The Canadian C7A2
Before the US Army approved the hybrid buttstock with the H6 buffer, the Canadians were already ahead of the curve. Faced with the same problem, they took a much more direct path than initiating an expensive testing program and fielding a new buffer weight.
Instead, they took the 4-position collapsible stock from the C8 carbine and stuck it on their C7A1 rifles with an H2 buffer. The new configuration was dubbed the C7A2.
In truth, the upgrade was slightly more involved than that. Rather than considering the collapsible stock as a temporary modification, the Canadian military chose to have C7A1 rifles rebuilt at the depot level as they went back to Colt Canada for maintenance.
This work included not only the new buttstock, but a new barrel, refinishing, a tri-rail adaptor at the front sight, and a few other elements.
Their original idea also included a KAC rail like the US M16A4, but they retained the plastic handguards as a cost-saving measure. The rifle also came equipped with the older ELCAN C79 optic, a predecessor to the SpecterOS found in my safe.
In all, Canadian troops took to the upgrade well. Though, like with the US military, the Canadian Army continues to steadily march towards issuing the 14.5” C8 carbine to everyone.
The USMC M16A5 Concept
That brings us to 2013. You see, both the US Army and the Canadians were already on the bandwagon with Collapsible stocks mounted to 20” rifles. Admittedly, the Canadians were more invested in the idea by turning it into a general issue weapon system rather than a temporary modification.
In January of 2013, Military Times’s Gear Scout blog published a blurb on a “unique” concept dubbed the M16A5 Armorer Conversion Marksman Rifle (ACMR) spotted at SHOT Show. The original article quickly disappeared, but the internet being what it is, the word quickly got around.
Howard at Loose Rounds captured the important bits.
Apparently, the USMC experimented with the Army’s H6 configuration but the commandant didn’t like it. They contracted with VLTOR to produce a product-improved M16A4.
The new concept had two primary differences.
The A5 Buffer System
First, VLTOR used their EMOD stock on top of their A5 buffer system. This tube was longer than the standard carbine tube but shorter than the full-length rifle version. It also included seven adjustment points for the stock.
This intermediate-length buffer tube was ¾” longer than the carbine tube and intended to accept a full-length rifle spring rather than the carbine spring. Similarly, it also used an intermediate-length A5-buffer that had some unique internal characteristics.
AR Build Junkie caught up with Nick Wantland, head of Marketing and Sales at VLTOR to ask some questions about the A5 system. Here’s a short excerpt, but check out the whole interview at the link.
The bottom line is that the use of a rifle-length spring alters the timing and recoil impulse of the system to be closer to that of a fixed-stock rifle.
In the end, that produces a smoother and more reliable weapon.
The Monolithic Upper
The other major change for the M16A5 concept was VLTOR’s use of a monolithic upper equipped with the newly-designed keymod interface. In 2013, the gun world was ablaze with monolithic uppers.
The idea focused on improving rigidity and accuracy by having the upper receiver and rail all machined out of a single piece of aluminum.
The idea was sound, but never caught on. There was the obvious hazard of damaging the rail meant replacing the entire receiver, but ultimately I think this time period in AR history was so full of innovation and “flavor of the week” accessories, as Howard at Loose Rounds put it, that people didn’t want to lock themselves into only one option.
VLTOR still markets their monolithic upper system as the VIS.
Your own M16A5 Build
Now that you know the history, let’s talk about building your own.
As I said earlier, the “official” M16A5 never came to fruition so there is no specific model to clone for yourself. That said, there are several concepts you can borrow from the design, as well as the Canadian C7A2 and US Army’s Hybrid Buttstock accessory.
The moniker of “M16A5” really applies to any combination of collapsible stock with a 20” barrel.
The Barrel and Rail
So the first rule of this game is that you need to start with a 20” rifle upper. My own version uses a BCM 20” Government profile upper that I reviewed earlier. Really any 20” barrel will do, but I think a lightweight profile will balance better with a collapsible stock.
Something like the Faxon 20″ Gunner would work great here for a field rifle.
There is no requirement for a free-floated barrel here.
The C7A2 uses the classic plastic handguards, and the Army’s H6 rifle came mounted on both the M16A2 and M16A4- neither of which was free floated. That said, there are some obvious benefits to giving yourself some rail-estate for accessories like vertical foregrips, bipods, lights, and lasers (if that’s your thing).
The real business happens at the rear end.
Both the US Army’s version and the Canadian model use standard carbine buffer tubs and springs. The Canadians use a standard H2 buffer while the US Army used a propriety “H6” buffer.
If you want to go the latter route, Damage Industries makes a commercially-available model.
Of course, the other path here is the VLTOR A5 system. That’s the most expensive “package,” though.
Since the M16A5 concept became widely known, a few more companies have jumped on the wagon. BCM makes their own intermediate-length buffer tube that’s compatible with rifle springs and VLTOR A5 buffers. The Magpul UBR 2.0 also grew in length to accept these components.
You can use a standard M16 rifle action spring, but I generally recommend the Sprinco “Green” spring as it has a longer life and just flat out works.
Like many things with the AR-15, the stock you choose for your M16A5 is pure personal preference. The US Army and Canadian versions used the standard M4 carbine stock. VLTOR’s concept for the USMC had an EMOD. The PS magazine cartoon version seemed to have a UBR.
So really, if you’re trying to be “correct,” any of those will work.
Beyond that, really anything will do. Keep in mind that not all stocks will collapse all the way down to be flush with the receiver. I know my MOE carbine stock does not, leaving about a half-inch of space. My ACS and EMOD go all the way down, though.
As you can see in the cluster of photos above, I personally ran with an EMOD for a while before switching to the UBR 2.0. I find the extra weight of the UBR helps balance the full 20″ barrel a bit better than the EMOD did. Both work great, though.
So there you have it. This M16A5 build guide was fun to research.
Even though I’ve had this configuration in my safe for a long time, I never really dug into its history at all. The collapsible stock on a full-length upper is one of my favorites to shoot, and I’ve run it in competitions and tactical classes alike.
Would I take it 100% of the time over something like a lightweight 16” barrel? Probably not.
As much as I enjoy the 20” barrel, I have to keep in mind the tradeoffs with weight and balance. The configuration came about for a place and time as a way to offer just a little bit of help to warfighters who were not issued shorter carbines.
If you have the option to use whatever you like, then this reason isn’t really a strong one for you. However, that still doesn’t diminish the fun of the configuration.