My 2 cents on the AR system

Both Uncle and Tam linked to what seems to me like an excellent article on the failure mode(s) of the M16/M4 system, which cemented, for me at least, a great deal of respect for the platform. If you haven’t read the whole thing, Do Read it.

It concludes (after much explanation of HOW the conclusions were derived);

“How to Deal With Heat Limits
The Training Answer: First, every GI should see those Colt test videos [of firing them to failure] and know what his gun can, and can’t, do. While the Black Hills guys were correct in noting that SF/SOF guys usually manually fire single shots or short bursts, even most of them don’t know what happens when a gun goes cyclic for minutes at a time. A good video explaining “why you can’t do that” would be a strong addition to training, not only for combat forces, but for support elements who may find themselves in combat and feel the urge to dump mags at cyclic rate.

The Morale Answer: Every GI should see the same done to AKs as well. There is a myth perpetuated by pig-ignorant people (like General Scales) that the AK series possesses magical properties and that the American weapons are crap. In fact, nobody I know of at the sharp end is at all eager to change, perhaps because the laws of physics and the properties of materials apply just as firmly to a gun originally created by a Communist in Izhevsk as they do to a concept crafted by capitalists in California. If you’ve ever fired an AK to destruction, you know that it grows too hot to hold, then the wooden furniture goes on fire, then, if you persist on firing it full-auto, it also goes kablooey. Not because there’s anything wrong with this rifle, but the laws and equations work the same for engineers worldwide.

The Systems Answer: As you can see from the Colt videos, if you clicked on over to Chivers’s article, thickening the barrel nearly doubled the rounds to catastrophic failure on cyclic. An open/closed bolt cycle might have practical benefits. They wouldn’t show up in sustained heavy firing like the destruction tests, but they might show up in how a weapon recoups from high temps, and open-bolt autofire would eliminate cook-offs, at least. But any such approach needs thorough testing.

The Wrong Answer: Replacing the M4 with something like the SCAR or the HK416, something that is, at best, barely better, that is much more maintenance intensive, and that, contra Scales’s assertion that his undisclosed client’s weapon is “the same price,” is twice (SCAR) or three times (416) the money. (The 416 mags are the best part of the system, though).”

I’ve fired over a thousand rounds in a day, both from an AK and a Ruger Mini-14, and didn’t come even close to failure, or even serious degradation of the rifles. (I haven’t tried it with the AR simply because my business hasn’t made products for it as yet) But then I’ve WORKED WITH steel since I was a kid, and know first hand how soft and moldable it becomes at high temperature, and I’ve seen how it can be “hammer welded” which is welding two pieces together that are red hot, just by hammering them together). And just about anyone who grew up on a farm understands “instinctively” that even the best steel becomes soft enough to bend like a pretzel, using nothing but hand and arm muscles, at high temperature, because THEY’VE DONE IT over and over. And so, without even having to think about it, it was natural for me to avoid over-heating the weapons. I’ve never had so much as a cook-off (again; as kids we sometimes cooked off naked rounds on purpose, because it was interesting and fun). I have no doubt than an AR-15 would do as well in a thousand round, one day test, though it may need a little attention to keep it cycling with the carbon that gets into the action. My Colt AR has been known to stop after about 350 rounds unless I keep it real wet (and depending on the particular ammo).

That one of the M4s in the battle related in the article was able to get through ~600 rounds in a very short time is pretty awesome. The physical limits of the steel were exceeded at that point, and physics is physics.

Another quote from the article stuck out to me as great. It addresses the trade-off between the ability of a weapon to fire an enormous number of rounds quickly without failure, verses the operator’s ability to actually carry it (because it’s too heavy). This may be a paraphrase, but it’s really close;
“You can carry it all day or you can fire it all day, but you can’t do both.” Yup. Take your pick.

But then if you’re unfortunate and pathetic enough to have gotten your technical and physics information from Hollywood actors you might believe that, “Fire doesn’t melt steel”.

I found it interesting to look at the “service life” of a typical rifle in terms of actual bullet-acceleration-in-bore time. If we assume a nice round number of one millisecond to push a bullet through the bore, and if we assume a nice round number of, say, 30,000 rounds to wear out the rifle, that’s a “service life” of thirty seconds. Compared to your family car’s engine, the combustion system in a rifle runs at awesome power levels, and with no oil pressure. Your actual mileage may vary.


21 thoughts on “My 2 cents on the AR system

  1. An individual infantry arm simply isn’t going to successfully substitute for a crew served water cooled or exchangeable barrel medium machine gun.

  2. I’ve taken a couple carbine classes where it was 1000 rounds per day. 1000 rounds / 10 hours = 100 rounds/hr. Just over 3 mags an hour. It doesn’t really get hot like that.

    • Good point. We did our “torture testing” in rather less time than that, being as our main objective was a high round count (product testing). We got ’em pretty hot – just not too hot. One test, which we repeated several times, was a 75 round drum followed by one or to 30s, semiauto just about as fast as one can jerk the trigger, reload, and keep going. That’s beginning to push it in my book. ‘Course the linked story was of a life and death battle– a whoooole different matter.

      So how did your AR hold up (if that’s what it was), as far as stopages/cleaning?

      • It’s a S&W M&P15, just a working class gun. The foreend is well ventilated which helps. And the last class would up being a total of 1060 rounds in one day with zero malfs. It started the day clean and at lunch all I did was spray a little Breakfree into the BCG. I shot it another 300+/- the next day with no malfs and didn’t clean it till I got home.

        • I would think you’d want to swab the bore a time or two before raking up ove a thousand rounds, but that is pretty impressive reliability. My Colt HBAR has never gone much more than 400 rounds without starting to need the forward assist to chamber. Maybe it just needs the Breakfree or something similar.

  3. “You can carry it all day or you can shoot it all day”
    Come to think about it you never hear about ship’s guns cooking off rounds. They aren’t built so much with weight in mind, anyway.

    • You didn’t read the WeponsMan articles and comments carefully enough. There’s a specific example of a navy 5″ gun cooking off, exploding (out of battery?), and killing several crew members on a destroyer during a Vietnam engagement.

      • You’re right, I missed that. That has to be a lot of shooting. I only knew about the one more recently on IIRC the Iowa.

  4. It should be noted that the H&K Infantry Automatic Rifle recently adopted by the Marine Corps is an AR that fires from an open bolt while in group therapy mode, and switches to closed bolt when switched to one shot per squeeze. It also has a heavier barrel profile than standard to deal with the heat better. Not old school Colt .950″ HBAR thick, but thicker than standard Government profile.

    • I have to re read “To Ride, Shoot Straight, and Tell the Truth”, I think the open bolt/ closed bolt switch like that was an item on Colonel Cooper’s Wish List.

        • ‘Twouldn’t be complicated to this 40 year musical instrument technician. Just one more “sear” and disconnector.

          Ever checked out the mechanism of a “Full Conservatory” oboe? No firearm comes even close, and the oboe must be able to “run” for hours on end, being humidified to the point of dripping wet and then drying out, often several times per day. They don’t run at 50,000 psi, sure, but they have to do a lot, and they can do it well and reliably.

          • I remember being shown an oboe by a professional, when I was a kid learning a simple instrument. Mind boggling. I’ll stick to my flute, a far simpler device.
            Then there is a pipe organ… 🙂

  5. Ooops, the H&K version does not use open bolt, the competing submission for the contract did, but was not selected. The H&K is a piston gun, though, so it does run cooler, and has a beefier barrel.

    • The 416 doesn’t run cooler, it just heats up different parts. While the ad rep is showing you how cool the bolt carrier is, he’s not showing you how hot the piston is.

      Plus if piston solved everything, then the M240 and M249 should never malfunction.

      Heavier barrels aren’t a complete solution. Although they have a greater heat capacity, they also take longer to cool down.

      • Greater diameter does equal more heat capacity, yes, and it also has more dissipating surface area, (by the increase in diameter x Pi, which is pretty significant) so it does dissipate heat faster, all else being equal. That it also holds more heat due to greater mass is not a bad thing. The only downside is in packing it around.

  6. Great article, and I agree.

    Still one VERY minor point. Do you think a SCAR-16 would still be twice as much if bought at replacement volume for the .gov?

    Again, I agree that the SCAR is only academically better than the AR series, and possibly could have a whole host of new problems because of the design differences (like issues with the reciprocating charging handles, or the polymer frame not reacting well to heat).

    • No idea, but these things are not difficult to test. There is a lot of “the AR is a proven design, with a proven supply chain, with current inventories, with current training doctrine, etc” to overcome. It would take more than a possible, marginal, or “academic” improvement to make a change worth doing.

      We’re probably doing something of a disservice by concentrating so much on the hardware. There’s been a lot of very good hardware around for the last 50 to 100 years or so. Things like principles, state of mind, awareness, coordination, communication and commitment probably go more toward winning a war than anything else. If you have all of that, your grandpappy’s gun hanging over the fireplace there is probably enough. Being on the right side is the first point, IMO. If you don’t have that, nothing is going to save you.

      • “Things like principles, state of mind, awareness, coordination, communication and commitment probably go more toward winning a war than anything else. If you have all of that, your grandpappy’s gun hanging over the fireplace there is probably enough.”
        thats what i say about our special forces when the argument of well this rifle is better because the bla bla bla uses it. If a group of seals, or deltas walked in to battle with 1903 and SSA no body is going to question them about it because good training and tactics can make up for the short comings of your weapons.

  7. Pingback: SayUncle » The AR-15 still doesn’t suck

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