Differences Between Canadian C7 and US M16

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According to user “RebelRouser” on AR15.com, the Canadian C7 rifle is a markedly different from the standard M16 issued to US armed forces. While the C7 is built off of the Technical Data Package from Colt, the Canadians claim to have made over 150 changes improvements to the basic rifle prior to entering production.

The most interesting nugget is the claim for barrel life. The Canadian design utilizes a proprietary steel that claims to increase barrel life 2-3 times over a chrome-lined 4150 barrel in US rifles. Further, the barrel has squeeze (reducing bore diameter over the length of the rifling) to increase accuracy.

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Hi Steve 
I apologize for not answering sooner. I‘m afraid I have been avoiding the 
alligators chewing on my ankles to take care of the ones feeding higher up. 
To answer your questions as presented: 
The effective range published does not have much to do with the barrel but 
is an infantry doctrine distance to do with the whole system including the 
man, sights, weapon ammunition and expected employment. So when you see 
effective range, it is almost always a subjective assessment of the system 
capability derived by the user instructor (CTC) and rifle requirements 
office (DLR), usually before the weapon is even bought. In the case of the 
C7 it included iron sights and was extended (I think) when the C79 sight and 
the C7A1 came along. The reference to the rifles origins (M16A1E1) is in 
reference to the sight option first chosen by the CF. The heavy front 
profile, 1 turn in 7inch barrel is definitely M16A2. As is the cartridge 
deflector, handguards and many other changes. 

Now lets talk barrels: 
The C7 barrel is not the same as any M16 barrel except for the exterior 
profile which is M16A2. The Material is to a formula developed here in 
Diemaco (under Gov‘t contract) so that the entire bore and chamber 
configuration can be integrally formed in one operation on a rotary hammer 
forge. This process produces a barrel that is much stronger than the US 
M16A2 barrel. The bore dimensions were developed to fire C77 ammunition, 
(Chamber, bullet lead, diameters) the bore has dimensional reduction as the 
bullet moves forward (squeeze) to increase life and accuracy. The bore is 
plated with harder chrome than the M16. This allows greater wear life (2 to 
3 times M16) and lets us machine C9 barrels from the same barrel blank. The 
SFW was recently tested and purchased by the UK special forces and won in 
competition against the Swiss SIG series rifles and the H&K G36 rifle. This 
barrel is now in use by the Special Forces in five countries and the US Navy 
Seals have expressed interest in putting them in the M4 Carbines that they 
have. 
We have just completed a C8 Carbine upgrade program for Canada which is a 
new barrel with an improved chamber and stronger extractor spring assembly 
and a weaker ejector spring. These are the same internal configuration as 
our very successful SFW barrel. 

Differences: 
The C7 rifle and C8 Carbine is made under license with a Tech Data Package 
provided by Colt to the Canadian Gov‘t. Diemaco reviewed the design and 
made about 150 changes to the drawing package before Canadian production. 
These are to numerous to mention her but include things like materials and 
processes as well as a different barrel configuration and manufacturing 
processes. 

The improved handguard we designed here after CWO John Ginn kept beating the 
Colt version off the weapon on the parade square. You probably can‘t tell 
from the outside but if the you take the handguard off, you will notice two 
types. The improved version has two large ribs under the heat shield and 
three interlocking ribs on either edge as well as different material. These 
were introduced late in the program so they had to be interchangable and be 
a good match with the old handguard. 

Another change you may notice is the small diameter front sight post that we 
developed when soldiers complained that the US large square one actually 
obscured the target at ranges of 300 and greater. 

I hope this helps you with the discussion and thank you for your interest in 
the C7. 

Ian Anderson 
ILS Supervisor 
Product Engineering Dept. 
Diemaco a division of Heroux- Devtek 

Please note: Any opinions expressed or implied in this email are personal 
are not necessarily those of Heroux Devtek or Diemaco 



Nathan S.

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

Nathan can be reached at Nathan.S@TheFirearmBlog.com

The above post is my opinion and does not reflect the views of any company or organization.


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  • Azril @ Alex Vostox

    Canadian C7, C8 series were chosen by the UKSF instead using the American M4 series. Enough said.

    • Zachary marrs

      That really doesn’t say much

    • Mr Mxyzptlk

      The C7 is barely better than the M16, it is pretty much just minor tweaks. UKSF had been using the M16 series since the 60s and the original M16s and M16A1s were absolutely knackered by the 90s so they needed to replace them. As they only needed a small number as they were only for UKSF, Royal Marines BPT and the Pathfinder Platoon, I imagine they didn’t mind the slightly higher cost for a weapon that is built to a better standard with slightly better reliability and longevity. They probably also got a good deal, what with Canada being in the Commonwealth and all.

      When they wanted an AR-15 carbine, the reason they picked the C8 SFW and CQB was that they had a pre-existing relationship with Diemaco and the SFW is a better weapon than the M4, in particular the barrel. I believe the C8 SFW also has a strengthened front sight block which is better for mounting the AG36 type launcher that the British wanted to use rather than the M203 type they had used on their M16/C7 rifles.

    • Joshua

      You must realise that the M4 was never submitted, just the C8.

    • phuzz

      Perhaps it’s because the plastic furniture is the *exact* same shade of green as on the SA80, and so they felt at home with it.

    • Joshua

      Oh yeah the rifles submitted were the C8, Sig 551, HK G36, and one other I forget.

      The C8 was the best performing entrant in the SAS trials and is the reason they adopted it, but at no time did Colt enter the American M4.

    • Bobbert91

      Bin Laden killed by German Hk416’s via SEAL Team Six. Enough said? Wait, what was the point to all this?

      • Joshua

        Because they adopted the HK416 back in 2004 when the MK18 was having problems(it was not yet a mature weapon) and instead of waiting for CRANE to get it working(took till 2007) they adopted the HK416 to speed up the process.

        You were saying? Although the 10th and 4th SFG as well as a number of units in SOCOM have done tests between the hk416 and the current Mk18(2010) and found no improvement and near identical performance between the two.

      • Anonymous

        A story ran in 2011 in the New Yorker claiming the SEALs who went on the raid to kill bin Laden were mostly armed with HK MP7 submachineguns rather than 5.56mm weapons of any type.

        http://www.newyorker.com/magazine/2011/08/08/getting-bin-laden

        Wikipedia contradicts this, saying the participants on the US side were armed with everything from belt-feds in 7.62x51mm to an assortment of M4, HK 416s, and SCAR-Hs, and suggests that any MP7s were carried solely as backups or sidearms, but I post the link here in the interest of completeness.

  • Canadian Vet

    Having used 3 different generations of C7’s and the C8A1, I can say a few things from experience.

    1- the C7A2 is very front-heavy since they replaced the solid stock with a collapsible one. When you start adding stuff like the PEQ-4 and a light, that muzzle can feel a but sluggish coming around.

    2- On the A2 variant, that ambidextrous mag release is a pain in the ass. I’ve lost track of the number of times I’ve had a mag clatter to the ground as a result of just carrying my weapon.

    3- The A2 cocking handle latch pin is a fragile piece of crap and I’ve also lost count of the number of times the latch stayed in my hand. Best guess, at the time they were using the same pin as they did with the original latch, but the added leverage from the extended one was too much for it.

    3- The C79 optic isn’t too bad, I’ve seen worse. But those backup/close-quarters rubber sights on top are completely useless on a good day and worn down to nothing at the worst.

    4- The sling swivels don’t play nice with single-point slings. The attachment tends to jam at the top of the loop and interferes with the cocking handle.

    However, I’ve never had any reliability or accuracy problems with either, so long as I did my part

  • Mr.T

    Diemaco was at least til HK416 the go to AR15 clone in SF community

    • Joshua

      Not really. The C8 and M4A1 are still the most popular AR variant in use.

      SAS still use the C8 as the L119A1 and are getting Colt Canade to upgrade the rifle to modern times.

      The only ones really moving to the HK416 are the ones who have had a long,history of using HK rifles and it is always easier to upgrade within a company than going to a new company all together.

  • mechamaster

    Good information. Maybe we need more information about how much commonality or part interchangeability between US and Canadian version. I love this kind of technical information. ( as long is not classified )

    • VolkCNC

      As mentioned in the article, most of the changes are in materials and processes. Parts commonality is near 100%. The most noticeable, and worst, difference is that the receiver rail on the flat top rifles is not true 1914 picatinny. The slots are a different spacing.

      • Paladin

        That’s because it’s a Weaver rail which we developed first, and the Picatinny rail was based off of it.

  • Interesting bit about the barrels. HK also advertises the 416 as having a taper-bore barrel and that it improves accuracy. I wonder what foundation that claim might be based on.

    • Paul Epstein

      The only explanation that comes to mind is that since the bullet is reduced in diameter and lengthened, that it would have a higher ballistic coefficient and thus shoot flatter and have a longer effective range (in theory). But if someone has the actual answer I’d be interested in hearing about it.

      • Rob

        The concept of having the smallest diameter of the bore at the muzzle is well known in rimfire target shooting. If there is a tight spot midway down the barrel, the bullet is sized down and once the bore opens up again gases can escape around the base of the bullet erratically as the bullet exits the muzzle. Having a mild taper towards the muzzle insures that the tightest point is near the muzzle. The taper will only be a few thousands of an inch.

        • Anonymous

          This.

          Colt Python barrels, once upon a time, were likewise made to be a thousandth of an inch or thereabouts tighter at the muzzle end.

          Hammer forging a barrel over a spiral mandrel is an old technique. Steyr has used it for many years. I have not yet heard of any benchrest records being broken with such a barrel, but that it appears to be a better way to mass-produce high quality barrels at low per-unit cost than cut rifling or button rifling cannot be denied.

      • John

        I don’t know too much about the science behind it, but the process of having the bore gradually reduced over the length of the barrel has been done for hundreds of years specifically for target rifles, and if they’ve been doing it this long there must be something to it.

      • Anonymous

        It might have some theoretical basis…but it’s utterly worthless if you’re shooting standard-issue garbage ammo.

        Manufacturers like to make endless claims about accuracy, and people eat it up, but no one seems to ever think about the harsh reality that a rifle system can only be as accurate as its least-precise component. Be it the shooter, the sighting system, the rifle, or the ammunition. Issuing a sub-MOA infantry rifle is, quite literally, a waste of money spent on higher-quality components and manufacturing processes to produce a rifle capable of shooting several times better than the ammunition that will be put into it.

        Conveniently, this also means that manufacturers have something of a free pass when it comes to claiming enhanced accuracy. After all, if it doesn’t work and the user sees no improvement, blame the (INSERT OTHER COMPONENT HERE). If it does work and the user sees better groups, then our wonderful new material/process/widget is a success! Given that you can safely assume 0.00% of the end users will have the knowledge or resources to conduct a proper evaluation of any given accuracy claim, you’re pretty safe saying whatever you want. Make the rifle heavier? Increased accuracy! Make the rifle lighter? Increased accuracy! Put purple polka dots on the handguard? Even more good better!

        • Tyler

          I have routinely seen guys shoot under 1inch with an issued C7A1/2 with regular C77 ball ammo. That was right from the butts looking up at the target. The weakest element is almost always the shooter.

    • Zachary marrs

      Lol, hk 416 improved accuracy

    • pete

      During ww2 the Germans created a 20mm cannon that could penetrate Soviet tanks by using some kind of tungsten tipped projectile fired from a tapered barrel, the theory being as the bullet is squeezed tighter the pressure builds increasing the velocity, as to improving accuracy, maybe if a 5.56 bullet is tight in bore for the last few inches before it leaves the barrel, it could make the flight path more predictable.

  • Pat

    Interesting that Colt Canada / Diemaco went through all this trouble to select a very high-quality barrel that is supposed to improve accuracy, and then the CF goes and mounts the Cadex Tri-AD directly onto the barrel as part of the A2 upgrade, which changes your zero and affects barrel harmonics every time something is attached / detached from the system (PAQ-4 / Insight M3X etc).

    I will second Canadian Vet’s comments, although I didn’t have too much trouble with the ambi-catch. Any stoppages I had were magazine-related due to damaged / worn feed lips or the awful black followers. Why the CF hasn’t kept pace with magazine follower updates is beyond me.

  • dan citizen

    I was disappointed when the phrase “a subtle scent of maple syrup” was nowhere to be found.

    • 1leggeddog

      That one is a natural “musk” inside of Canadian Armories

    • C.

      The C7 and C8 will also chamber poutine and when it fires, there’s no bang, but a very loud “eh”.

  • dp

    Hundred something changes? No way. Yes, new barrel (due to process), sight post and hand-guards (later on). All the mechanics plus both receivers were exactly the same as licensed. There was plenty of experimentation with plastic (Thermold) magazines with rather unsatisfactory results.

    • Rusty Shackleford

      With the Thermold mags, Supposedly the company that designed them used a special Dupont thermoplastic for its construction and suggested they be made the same way when licensing the TDP to Canada, but some bean counter decided to go with a cheaper plastic which caused poor performance.

  • Paladin

    There is also a thread on CGN where one of the Diemaco reps explained some of the changes made for the C7 and C8 rifles.

    For example, the C8 is built with a 15.7″ barrel rather than a 14.5″ or 16″ as is otherwise common, because through testing they found that 15.7″ is a vibrational node for the specific barrel profile used, which enhances accuracy.

    • Sam Schifo

      Manufacturers always seem to forget about barrel harmonics. They usually just cut the barrel to an arbitrary length, when an inch longer or shorter will make a significant improvement in accuracy.

      • Paladin

        Indeed, I was actually quite impressed with the amount of effort Colt Canada (Diemaco) put into barrel length selection. Because of the way they do the CHF they couldn’t simply take a reference barrel and trim it down until they found the vibrational node, they actually had to forge entirely new barrels for each length tested, then mount them and test them for accuracy. It’s that kind of dedication and attention to detail that leads me to believe that the C7/C8 family may well be the best AR15 pattern rifles in military service.

        • Sam Schifo

          I completely agree. Diemaco has put more thought into the design than anyone else, and it really shows in the final product. Now if we could only get some civilian versions down here in the US.

          • Paladin

            I’m sure Diemaco would love to sell them in the U.S. market, but you guys would have to deal with that pesky 922(r) thing first.

          • Anonymous

            Perhaps someone brighter than I could bring suit, claiming that NAFTA overrides 922(r).

            …well, it was just a thought. I am not a lawyer.

          • floppyscience

            We have plenty of lower receivers. Maybe they could just sell us some parts kits. 😉

  • Bunglezze

    Hey, why do we care what guns a bunch of hosers use in the great white north? Take off!

  • idahoguy101

    The Danish and the Netherlands militaries bought their rifles from Canada. Why from Canada versus from Colt? IDK… Price? Maybe…but I bet the Canadians were polite and the Colt executives were jerks. Anyone else have that opinion? If I were to buy a new Honda from one of two dealerships for the same price, I’d prefer the dealership that treated its customers with respect.

    • Joshua

      Because sometimes dealing with other countries export laws is easier.

  • GeniusBandit

    One is green, the other is black. There, thats all you need to know.

  • Wetcoaster

    You know, now that Diemaco is selling to civilians, there isn’t actually need for speculation. You just need to find a Canadian reader with a 6920 and a C8 with the right instrumentation to compare them. It’s probably just a matter of time at this point since both rifles appeal to the same demographic. (New 6920s used to retail for $2900 CAD and seemed to have no shortage of buyers, so the new C8s are already starting nearly a third cheaper than 6920s used to be. 6920s are cheaper now, but that’s another story.)

    • Ge

      I wouldn’t mind having a Semi C7 near-clone. Canada can keep its thermold mags though

      • Wetcoaster

        I think they’ve switched to USGI style magazines. All the pictures of troops in the field seem to show them.

        • Ge

          Yeah, if I recall correctly, the Canadian Thermolds were intended to be another attempt at Stoner’s idea of a disposable magazine.

          They came preloaded in a wrapper and were intended to be tossed once empty. Of course logistics got in the way and soldiers needed to keep reusing those magazines.

          The thermolds weren’t intended to play the role of constantly abused magazines, which led to reliability problems. Hence the switch to USGI style re-usable magazines (which is funny since those were also intended to be disposable)

  • n0truscotsman
  • Rusty Shackleford

    Didn’t Colt buy Diemaco, now called Colt Canada? Why doesn’t Colt use these barrels on U.S. made AR15s if they are superior?

  • Holdfast_II

    Also, the C-7 is full auto, despite being otherwise A2-like.

  • smith934

    When was this letter written? Diemaco has been owned by Colt since about 2005, I think.