The Low Maintenance Rifle Project

LMR project

Medium has published an interesting article on the Pentagon’s search, back in the 1970s, for a rifle that required little maintenance. Joe Trevithick writes ..

DARPA asked TRW for a rifle that would solve these continuing problems. The new weapon had to be simple to build and easy to use and must resist corrosion.

The gun also had to have “semi-permanent solid film lubrication.” Solid film lubes are effectively painted-on … and only require periodic touch-ups.

By contrast, soldiers had to regularly grease up their M-16s. Dirt, sand and other debris could cling to the lubricant and gum up the rifle.

The new LMR also had to be accurate, even when firing on full-automatic. Reports from Vietnam suggested soldiers were not shooting accurately, even if the exact reasons were unclear.

They were, of course, solving the wrong problem. It was far easier to simply fix the M16 issues. Still, I do wonder if concepts from the prototypes could be adapted into modern maintenance free survival-type semi-automatic rifles.

Thanks to Fred for the tip. 



Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


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  • Jabberwocky1

    LMR? I believe that’s called an “AK47”

  • Wayneregina

    Interesting how similar that concept rifle looks to the Keltec Sub2000

    • An Interested Person

      I would say it looks a bit more like an FG42.

      • the ammo addict

        It uses an M-60 pistol grip. I wonder what other existing parts are hidden inside. I would love some info on how this thing works. It looks very sleek and simple.

        • Tassiebush

          it’s roller locking with gas piston, fires open bolt in full auto only courtesy of m60 trigger group.

      • Tom

        especially the placement of the magazine.

        • Tassiebush

          it’s side mounted

          • Tom

            Ops replied to myself above. But yes the may is inserted horizontally to the left if the receiver just above the pistol grip.

          • Tassiebush

            haha we’ve all done that at some point. yeah it was a statement. more punctuation needed on my part.

          • Tassiebush

            I’ve posted a link to article on forgotten weapons about this gun which is awaiting moderator approval. it has a lot of technical details and the manual.

        • Tom

          Not sure if that’s a question or a statement but if it the former then yes the magazine is mounted to the left if the receiver straight above the pitol grip just as per the FG42.

      • spotr

        The number 4 LMR prototype is very similar in appearance to the FG42.

      • Sledgecrowbar

        I think it looks so much like an FG42 that I wonder just how much of the design is original. The M60 was designed directly from the FG42, so at least the trigger group suggests similar internals.

    • guest

      I thought that’s what the article was going to be about.

  • Tom – UK

    Answer to this problem is the AK-47/74/12

    God I want one

  • iksnilol

    I remember reading about this thing a couple of years ago. For a low-maintenance gun I was always thinking an open-bolt blowback in bullpup format (I know, I know, Doesn’t sound particularily safe). Would be short, have the full 50 cm barrel that is required for 5.56 and would be simple. Maybe the bolt would be a bit heavy but I was thinking telescoping bolt could solve some balance issues. And the bolt could be hollow and be filled with tungsten or lead to provide extra weight without taking more space.

    • Tom

      There is a very good reason you do not see blowback assault rifles, physics be a hard mistress. In order to have sufficient resistance to seal the breech you would need a very very heavy bolt which in turn would require one hell of a spring. You could of course go along the gas delayed blowback route but then you are moving up in terms of complexity and might as well just go for a piston and rotating bolt.

      • iksnilol

        5.56 requires a 3.2 kg bolt (7 lbs) according to Orions Hammer. That is for closed bolt, for open bolt blowback you can generally cut the weight in half. So while it wouldn’t be the nicest rifle it would be simple and it would work. Spring doesn’t have much to do with it, it won’t slow down the bolt enough to be a part of the calculation. There have been a deal of 5.56 automatics made that were open bolt. The designs use a telescopic bolt that sleeves around the barrel. So balance isn’t affected much.

        + I have been playing Fallout 3 lately and I am a bit annoyed at having to maintain my weapons.

        • Tom

          The problem with the spring as I understand it would be cocking the thing. I just can not see that by the time you have a rifle that heavy and with that much steel in it that you have saved a lot. Its not like a locked breech gun is that hard to make for any industrialised nation.

          Of course thats not to say there are not lesson to be learnt here. But that seems to be the way of the military industrial complex they identify a problem (that may or may not actually exist) spend millions developing and trialing a replacement only to decide its not sufficiently better to justify replacement but then nether do they look at incorporating those improvements into the current design. For example of the polygonal rifling of the XM8 was so great why not put it in the M4?

          As for Fallout just get a zero degradation mod. Its not like its cheating as the weapons degrade far too quickly. Especially when you consider that according to Fallout lore many weapons are newly manufactured. Then get a realistic weapon damage mod and have some fun 🙂 Also I have to recomend the classic Fallout weapons pack – the 14mm SIG pistol is actually a good weapon!

          • Tassiebush

            For straight blowback it seems that cocking weight isn’t the issue you’d expect it to be if bolt weight is heavy enough. Apparently the vg1-5 in 7.92×33, which is meant to be gas delayed blowback actually works just as a blowback albiet with 6lbs of reciprocating mass. If the bolt were lighter then the spring would have to be much heavier. Another few cool straight blowbacks are winchester 1907 and 1910 rifles. As Iksnilol says too if it’s an open bolt blowback forward momentum negates need for as much bolt mass.

          • Tom

            As I understand it 7.9mm Kurtz is quite low pressure which would help in a blowback. But I just can not see a blowback in 5.56 working that well. Even using API to lighten the load.

            As production changes so do the economic of things and thus I do not see how a blowback assault rifle would be any cheaper to make than say an AR18 or AKM. And whilst its a simpler system that does not make it necessarily more reliable or reduce the need for maintenance. Plus accuracy would suffer. But having said all that it would be great if someone made and oversized Sterling SMG in 5.56 you know just for the giggles.

          • Tassiebush

            I agree there isn’t really a good cost argument for a blowback especially once you factor in performance and modern manufacturing. Another big factor is that at the economy end of market there is lots of more sophisticated surplus stuff which would outperform a purpose made cheap blowback without costing any more. I totally agree it’d be cool to see it made for the giggles though. the pressure of a .223 would have to be higher as you say and it might not agree with direct blowback. I’m guessing fluted chambers would be required.
            the sole niche for a blowback 5.56 would be where other guns were unobtainable.

          • Tom

            I think fluted chamber and API would be the way to go. Just stand well clear when its fired :).

          • Tassiebush

            haha or a kevlar curtain over ejection port to take the edge off and make up for lack of design finesse!

          • Bert

            Here’s one in .308 courtesy of ForgottenWeapons:

          • I believe that is lever-retarded blowback.

          • Tom

            I believe sir you are correct. Firing from an open bolt. It was designed as an emergency replacement for the Bren in the event of the Cold War turning hot.

          • dan citizen

            The “R word” is a hurtful term…. It’s now preferred to call it “lever enabled blowback”

          • Tom

            If the magazine does not feed from the side its not a Sterling 🙂 also thats more of an LMG than an assault rifle.

        • Blowback doesn’t really simplify maintenance all that much, it mostly just makes the gun cheaper.

  • echelon

    So that’s where KelTec got the Sub2k design…

  • iowaclass

    That looks so “Empire Strikes Back” prop department.

    • Marc

      Blaster rifles were built of FG-42 props.

      • Tom

        Lots of real steel weapons were used in Star Wars mostly WWI and WWII era ones. But I think the FG42 was not one of them. The Imperials mostly used Sterlings with Lewis Guns, MG34 and MG15s as LMGs.

        I think you may be thinking of the Rebel blaster used on Hoth which was based on a casting of the STG44.

        • snmp

          FG-42 is base on the Lewis Guns

  • Pedro .Persson

    I can think of something along the lines of a simplified and more modular G3 would be ideal. A roller delayed blowback is the simplest form of cycling mechanism that is viable on an intermediate/full-power rifle cartridge (no gas system at all and a fixed barrel.) It’s not the nicest system, it recoils hard, fouls a bit and is picky with ammo selection… but it’s extremely simple to manufacture, care of, repair at the field level, very accurate due to the fixed free floating barrel and very, very reliable WITHIN its design parameters of ammo… which is a non issue if we are talking about a military rifle with a supply of a specific palette of variations of a given round. Now if you want something a bit more flexible and less dirty, a roller locked system, be it recoil or gas operated, fits the bill nicely while still being simpler to manufacture than a proper rotary bolt. Now if you want something “nice” outside of a niche semi-auto precision rifle, go look somewhere else… a rotary bolt is not that much more expensive or hard to make and does everything the RL does better (stronger, better locking, less parts to loose, less wear on the locking mechanism, no issues of synchronization/symmetry that can lead to a catastrophic failure, etc) that is why the RDB was born in the first place. It was truly cheaper to make and objectively better for the intended role. Probably one of the thing that helped to kill this rifle: Not cheap enough.

    • Albert Einstein

      Stoner’s direct impingement and Kalashnikov’s long stroke piston systems are WAY more simple than G3 systems.

      G3 was only simpler on paper. G3 has way more parts than AK, and way more parts than AR-15 pattern guns.

      G3 also requires more maintenance than an AR-15 type weapon, since it fouls up far worse, and the roller bearings wear out, which means you need to replace them, or risk early unlock(the gun already unlocks extremely early) and a far more serious issue.

      On an AR-15, you just change out the bolt every 15K rounds if you’re running an SBR, and call it square. You can go ahead and not do that, while checking every 1k rounds for cracks/stress marks after you pass 15k mark.

      G3 also INTRODUCES an issue of symmetry when it comes to the rollers. There’s a reason why rollers and flaps/arms no longer used in guns: they’re too problematic. If one’s weaker than the other, it’ll take the whole load, break, and then you got a horrible week.

      The G3 also was never simpler to maintain. It was only “simpler” to maintain because you COULDN”T MAINTAIN IT AT THE USER LEVEL. Guns like the AR-15 and the AK were designed to be maintained by the users, while the G3 was designed to be maintained by an armorer.

      • Pedro .Persson

        That is mainly because the G3 was quite refined over the original concept (a proper service rifle), like the AR DI system is if you compare it to Ljungman. And more parts don’t always mean more cost or complexity, what matters is their geometry and manufacturing process, it’s not rare that at the end of the day that elegant monolithic part costs several time a collection of welded and bolted smaller parts of much simpler geometry. The RDB has this potential to be simplified to the extreme while still being a “useable” gun (you can use ball bearings if you insane enough.) Cleaning and servicing is mainly a matter of design than of the operating mechanism per se… but on a semi-disposable rifle anything beyond the most basic field strip is not really a priority but really a luxury.
        Remember the AK might be cheap and has a LOT of compromises in the name of saving a few cents, but it’s still a “nice” gun with all the qualities you mentioned. The AR can be made cheap… but the design does not fare well when you drop bellow Vulcan Arms quality… This LMR is basically a modern less crappy rifle version of a Liberator, but still ultimately a semi-disposable last-ditch weapon with a fancy name… not that it makes the concept good, or even feasible, but it’s what it is and the rifle needs to be judged for what it proposes itself to be. And that is why durability, fouling or even the bad apple that is going to explode on the face of Mr. Insurgent of the week… it’s not meant to arm a proper fighting force but to keep the miserable people you arming with junk not to die with empty hands tied and blindfolded against a wall before, for long enough until you actually send or care to send proper help.
        In the end you are right, a AK is not that much expensive and is actually a decent weapon (really great if well made and modified like the numerous derivatives to lesser or greater degrees prove) so a better investment.

  • derfelcadarn

    They were attempting to fix the M16 issues by replacing it, it would have required thirty years less time.

  • Adobe

    Those look 100% photoshopped.

  • the ammo addict

    Thanks!

    • Tassiebush

      My pleasure!

  • Harrison Jones

    Something like this for sub $250 would be awesome. To bad the concept didn’t go further.

  • Bob

    Maintenance? I just rub a little bacon grease on the rounds and I’m good to go.

  • Zebra Dun

    Remington M-66 rifles used nylon roller bearings I believe for lube.

  • dan citizen

    G3 or AK, that is all.

  • EthanP

    I believe this rifle was intended for indigenous personnel, not US troops. The theory was that these troops would/could not clean nor fix their weapons.

  • Markdown

    What about light gas gunpowder NH3-BH3 ?

  • fmike15

    Wow, fallout 3, Star Wars props, photoshop. Some serious comments here. Actually this gun got some mention in the 13th edition of Small Arms of the World back in the 70’s. Yes it’s a real gun.

  • hackenslash

    If manufactured with a detachable/replaceable barrel, would have made a useful LMG, especially for the guys in Vietnam.

  • Albert Einstein

    It’s like someone yelled “Kalashu akbar!!” and all the AK fanboys came out to play