US Advanced Combat Rifle Video

We had this video pointed out to us by reader Cris – a 1990 film put out by the US Army detailing the four rifles being put into testing to become the Advanced Combat Rifle. It was to replace the M16 as soon as 1996 – so we can pretty much tell that it all came to naught. The plan was one that had been around in fits and starts since the early 1960s: replace the single-bullet cartridge with a multiple-projectile round so as to increase the chance of scoring hits against fleeting targets in a  combat environment.

For the ACR program, the contenders were:

  • Colt ACR – Basically an M16 firing a duplex cartridge
  • Steyr ACR – A polymer-bodied bullpup rifle firing flechettes
  • AAI rifle – Advanced Armament Inc had participated in these programs all the way back to the 60s, and they entered a flechette-firing rifle as well
  • H&K G11 – A bullpup firing caseless ammunition with extremely fast 3-round burst capability

Anyway, I’ll let the video give you more details (they start talking about the ACR at about the 3-minute mark). Among other things, I found it interesting to see the emphatic recoil of the G11. Also, I want a testing range like the one built for this testing! 🙂

Thanks for sending the link, Cris!


  1. It is a damned shame they did not have that range set up when I went through Ft. Benning back in the seventies. That setup looked like one hell of a fun shoot!

    • In theoty, the oposing resistance/ stiffness of shoulder should not have mattered much. The free recoil of mechanism inside outer shell during 3round burst is supposed to ‘look after itself’ and it does. The outer manifestation you see as final kick is an ‘aggregated residual’ recoil after mechanism’s bottoming. At that time all 3 are already out and possibly in the target area.

      The solution chosen, being ‘caseless’ round was specifically to cut extraction and ejection phase, thus speed-up cycle time. Novadays this is often mis-interpreted as though the ‘caseless’ is meant as progress by its own existence. It cuts on weight of shot, true. Question is if this is worth of gain in pursuit of such complex technolgy.

      • The caseless round reduces raw and processed materials requirements, i.e., the cost and weight of a cartridge case, and is additionally more compact (much shorter but slightly larger in diameter) since the projectile is recessed in a blind-ended hole in the formed propellant. Caseless ammunition really belongs to the family of so-called Telescoped Ammunition, which features both Caseless and Cased Telescoped Ammunition (CTA), which latter uses the same basic technology in conjunction with a hard cartridge case instead of formed propellant.

        In an interesting aside, both H & K and GIAT apparently exhibited prototype drawings for caseless machine-guns in various calibers at assorted defence expositions in the 1980’s and/or 1990’s ( SATORY, etc. ).

        • Yes Earl, I am familiar with the subject. What may be added is that there are 3 distinct issues (of better difficulties) when handling CT or/and CL. First is awkward shape – it cannot be just stripped from mag in conventional sense. Another 2 are specific to CL: very difficult to seal-off in reliable way in long term and finally no means to remove heat from chamber thru ejected casing. I am very skeptical about future for this technology in small arms.

          Designers are looking for ways around it. One such case in AN94 (Avtomat Nikhonova).

    • It’s because the shooter is firing in burst. The barrel and breech in the G11 recoil during the burst, which delays the recoil on the shooter. This also means that the recoil is the recoil of all three shots, “stored up” to hit the shooter at once. 4.7x33mm is about equal to M193, with a bit less recoil from the slightly slower bullet, and probably a bit more recoil from the propellant gas, since telescoped ammunition tends to be less efficient in this regard.

      3x M193 recoil in a nine pound rifle is going to be a handful.

      • Exactly. And unlike ordinary rifles the recoil arrives at the shoulder only after the third bullet has left the barrel.

  2. Does anyone have further information on how the AAI entry worked? The Colt entry is just an M16 with go-faster stripes painted on it. The Steyr is interesting, and information is readily available from the European Patent Office. Information on the HK design is easy to find too, but it makes my head hurt.

      • I don’t know what definition you use. There might be discrepancies. In the SPIW program a “Serial Flechette Rifle” or “Serial Bullet Rifle” was a rifle that fired its (lightweight) bullets/flechetes at a very high rate. The COLT ACR fires a duplex or a conventional cartridge at a rather conservative rate of fire.

    • There is very little known about AAI contender’s internal mechanism. It is closely related to previous generation of ‘small arm innovation’ – this being Salvo project from 1960’s. According to my info it was percussion fired in selective mode.

      There was book named “The SPIW”, published by Collector Grade Books (1984) authored by R.B.Stevens and E.C.Ezell which describes that part of history.

  3. Here is some relevant reading on history of multiple projectile rifle shots. The Colt’s design was not first by any means. By some leaked news from the time of tests the separation of 2 bullets never took place; the basic idea is plausible however.

  4. I remember all this being covered by a long defunct magazine called International Combat Arms. Always thought the Steyr ACR was the best choice here.

  5. In 1990 the cold war was sort of still on. The Berlin wall had come down, but it was before Yeltsin. Given the long distance / non-urban combat scenarios it looks like they were looking for solutions to not quite the real looming problems. Streets of Somalia were to be a bigger issue than the plains of Europe.

    Can anyone shed some light on the flechette issue? Is there something to the concept, or just an interesting theory? I recall reading books published in the 1970s about them being the future.

  6. I’ve always been fascinated by the G11 and I wish more had come of it. I also wonder how many were made/still exist.

  7. As a follow-up to my comment to Denny above, a real problem with any kind of telescoped ammunition, caseless and cased telescoped ammunition (CTA) included, is that a lot of the propellant gases are wasted by venting through the barrel before the bullet becomes properly seated since the bullet itself is positioned at a distance behind the bore.

    Ares, Inc. and European consortium CTA International, which carried out extensive R & D on the CTA concept, used a secondary charge in the cartridge which effectively pushed the bullet into the rifling of the bore to create a gas seal before the main propellant charge ignited. This solution was, surprisingly, first applied to the German 88mm Flak 36, 37 and 41 AA guns of World War II fame, but for different reasons. The high chamber pressures and temperatures tended to erode the first few inches of rifling to the point that a lot of propellant gases were wasted since the projectile could no longer be seated firmly in the bore. According to Ian Hogg, the remedy was to install a small gunpowder charge immediately behind the shell and ahead of the primary smokeless powder charge, with a flash tube extending from the primer in the base of the cartridge. When the primer was activated, the gunpowder charge would be immediately ignited, pushing the shell into the rifling before the main charge exploded.

    In 1989, Ares introduced the gas-operated 50-cal. Telescoped Ammunition Revolver Gun (TARG), designed by Eugene Stoner. The cartridge case was made of plastic and the recessed projectile was basically the standard M33 ball round. The revolving cylinder had four chambers and a cyclic rate of fire of 2000 rds./min. The completely cylindrical and rimless cartridge case greatly simplified the extraction and ejection process, as these steps now only involved pushing the expended cartridge forward and out of the chamber while a fresh cartridge was pushed in behind it. The TARG prototype was 44.4 inches (111 cm)long and weighed 45 lbs. (20.46 kg) empty, a considerable size reduction compared to the service-standard Browning M2HB made possible by the telescoped ammunition. The last that was heard of the TARG was that a company called Alliant Tech Systems took over development in the late 1990’s, then shut down the programme.

    CTA International reportedly developed two CTA technology demonstrators, a 50-cal. HMG and a 45mm automatic cannon. The former was a four-barreled Gatling-style mechanical gun capable of 4000 rds./min. The latter was equipped with a transversely-pivoting chamber that enabled a fresh round to be fed from one side while the spent case was pushed out the other before the chamber swung back into the fore-and-aft (firing) position. There is a good illustration of this process on Page 233 of Ian Hogg’s “Machine Guns” (Krause Publications, 2002).

  8. The H&K G11’s burst system brought to mind the Russian Nikanov AN-94 with its similar high speed 2 shot burst mechanism. What ever happened to this rifle? I thought the Russians adopted it, but the last I ever heard was a 2,000 piece production run for troop trials.

    • From what I understand, the Russians have simply not had enough funds to entirely update their arsenal. One of the reasons Izhmash went bankrupt.

    • Not in production and not considered for it. There are 2 reasons for it – cost (about 2x that of AK74) and concerns with recruits/ drafties not being able to maintain it properly. (Russia has conscription military service).

      In simple terms it is just too complex; so was G11 and even more so.

      • I did some work in Portuguese speaking parts of Africa a few years ago, and inevitably ended up working alongside South African guys who’d got to know the places during the decades long “civil” (proxy) wars.

        They had huge respect for the relative indestructability of AKs compared to other rifles, regardless of the perceived qualities of the guys who were using them.

        I saw a few VZ58s too, but never up close.

        • The FAL is also pretty indestructible. It’s one weakness in GI-proofing, compared to the AK, is the magazine. Some of the poorest countries in South America still have their original FALs from circa 1959, with every speck of finish worn off from cleaning in tubs of mogas with wire brushes. But they’ve had to suck it up and restock on mags from time to time. A peacetime draft army is a pretty reasonable test of a gun’s durability, because “who ever washed a rental car?”

          Of course, the only reason there’s any rifling left in those barrels is that the 5 decades of draftees that have handled them don’t always get any ammunition to fire.

  9. I once skimmed through a .pdf of the research report which eventually spawned the .223 Rem and the M16. I didn’t save it and can’t remember the date and title.

    The central paradigm which the report presented and then worked from, was that analysis of encounters with the enemy (Korea, and maybe some early stuff in Vietnam) tended to occour by surprise, and in the frightened confusion of the short encounter, very little if any aimed fire took place, and any hits tended to be random chance.

    Based on that, and the (probably valid) assumption that beyond about 300 yards, the average soldier couldn’t hit anything anyway,

    the reasoning continued that hits were more likely if there were more lumps of lead in the air, and if the max effective range of the firer was 300 yards (or so, and working from some “stopping power” formula weighted heavily in favour of velocity) then, a .22 centrefire would allow more bits of lead to be carried to randomly throw into the air in a mad panic.

    In a single phrase; spray and pray.

    Implicit in this, appears to be the assumption that soldiers would be poorly trained and panicky

    That they would likely have been conscripted to be thrown (at minimal cost to precious military budgets) into the meat grinder.

    I know that sounds provocative, but I think that was the case.

    I suspect that the same thinking still pervades weapons research projects.

    • cont:
      Following from that; the G11 is an interesting bundle of contradictions.

      The lighter ammo would certainly allow either more to be carried or a lighter pack for the same firepower.

      The 3 shot salvo feature – is neither a spray and pray, nor with the final recoil which we saw in the vid, likely to produce a severe flinch in the assumed 19 year old conscript, is it conducive to calm, aimed fire, or to watching through the optics to see where the bullets went.

      I’d also be curious about the barrel heating effects of leaving the gun in 3 shot mode, especially when there is no brass case to carry most of the heat out of the gun.

      was it an example of saving weight on the ammo, only to have to add weight to the gun to provide a heat sink, and to add to the inertia of the stock/chassis assembly, to hold it steady during the burst and to soak up some of that recoil when the working parts hit their buffer?

    • You may have a good point there, Keith. Given that the 5.56mm x 45 cartridge and the M-16 rifle were adopted for U.S. service during the early 1960’s, during a period only a little over a decade after the Korean War and during the early stages of the Vietnam War, and that both wars involved extensive deployment of quickly-trained draftees, it would not be surprising if the military authorities had taken this into consideration.

    • I do not see it “provocative” at all, Keith. What you are saying is still very realistic and will likely remain that way. What appears as abberation of what was found in A-stan was because a) nature of ‘virtually empty’ countryside, b) dis-proportional character of opponet’s capabilities. Regardless of that experience, we can quite reliably state that more time available allows for more aimed fire and the opposite applies when there is action on spur of immediate response. In second case, capabilities of weapon when comes to accuracy go out of window.

      This knowledge probably led to concept which seems nobody mentioned yet and which will be of interest to many. This is the fact that one of initial contenders was E.Stoner thru ARES (maybe Earl mentioned something in that connection already). However, Stoner was in disagreement with specifications and withdrew from contest lately. His concept was a weapon closely related to doctrine you describe: lots of bullets in short order and up to 300yrds mode. This is very close to AK way of thinking you talk about. And yes, his conceived shot was of CT type, packaged in synthetic casing.

  10. As Denny has pointed out, one of the most significant problems with caseless ammunition is the lack of adequate heat dissipation. One can only make the barrel, chamber and bolt so heavy to act as a heat sink before the weapon becomes too unwieldy on the battlefield, and even the heaviest barrels are not entirely immune to overheating if firing goes on for long enough. In that light, if one must use non-conventional ammunition, Cased Telescoped Ammunition might be a better option since it confers the advantages of short overall length and a fully cylindrical, rimless profile that simplifies extraction and ejection while retaining adequate heat control and eliminating the other major issue Denny brought up concerning caseless ammunition — relatively poor durability of the exposed formed propellant vis-a-vis a conventional cartridge case.

    I suspect that the G-11’s Achilles heel in terms of overheating would show up fairly quickly if too many consecutive three-round bursts were fired in rapid succession, with all the attendant potential problems of ammunition cook-off and loss of accuracy.

    • Right, managing heat is key in auto weapons development and failure to manage heat leads to lots of problems, from barrels that expand and lose accuracy (the very first result of long bursts) to various mechanical problems (especially with dissimilar alloys in the gun, that usually have dissimilar expansion rates and ratios), to the mother of all heat problems, cook-off.

      One part of US Army auto weapons testing has been probing for what conditions produce cook-off. This is done with lots of safety measures in place — definitely one of the “don’t try this at home, kids” tests because while a cook-off in a locked breech is merely a data point, a cook-off before lock is achieved can get ugly. (I suspect some of the kB!s we see on the boards are this).

      I think caseless ammunition is a dead end, given present technology. The G11 was a fascinating failure. The brass case serves several purposes, but two of the most important are seal and heat sink. Current boffin thinking seems to run to cased ammunition (telescoped or not) replacing the brass with a lighter material, a polymer of some kind, which might mimic the obturation of the case and answer the gas-seal use case.

      But I can’t think of any polymer material that will replace the case as a disposable heat sink. As anyone who’s ever had a fresh hot casing down his collar can attest, a lot of waste heat exits the gun embedded in those things.

      • It was always one of those difficult to broach subjects;

        when someone brought the new lady in their life to the range, and she was wearing a low cut top…

        How to incorporate some ammonium salt (which is non corrosive and which won’t leave any residue) either into a plastic case as a filler, or as a layer in a plastic case, so it doesn’t absorb heat from the burning charge until the propellant gasses have completed their work?

        a much more difficult subject…

      • The secret of polymer cases is that they act as insulators that prevent heat from going through the case at all and thus reduce the heat transfer to the gun. They are also very cheap to make compared to brass or any other metal cases.
        However, you are very wrong about the future of caseless ammo. It is coming for Armies the world over because it has so many logistical advantages that they can not afford not to do it!
        Regardless of all the speculation on the G-11 and it’s ammo, the Germans had bought the gun and ammo, hook line and sinker! There were o problems as mooted in this or any other thread!
        For two interesting tid-bits of info see these links; By the way, this is not the one I was looking for, that one fired 1,050 rounds with one pull of the trigger!

    • Because the G-11 used Moderated RDX plastic explosive for the propellant, it did not cook off nearly as easily! In fact if you only used the 3 shot burst and fast singles, you could not carry enough ammo to over heat the gun to the point it would start “cooking off”! The barrel and chamber reached “Equilibrium temperature” long before the ammo reached it’s critical temp.
      In addition, the ammo resembled a small block of hard plastic that you would have to use tools on to damage. The Germans had put several thousand G-11s in to troop trials for a year or three and had made the choice to buy them for the whole Army when the wall came down and they were broke absorbing the East Germans back into the fold. There were no significant problems with the G-11, or it’s ammo!

  11. Thanks Earl, I guessed that was what you were replying to.

    I really should be trying to find that report again, I didn’t bother to save it, but I’ve been thinking over some of what it contained for the past few months.

    One thing which struck me was the implicitly very low opinion of the authors towards the young soldiers who’d be using the weapons, expressed in a report for a military readership, compared to the material which was produced for consumption by the general public, which never failed to sing the praises of the brave young men.

    admittedly they did present a historical and an empirical basis for that opinion, and their remit was to recommend future directions for individual weapon development – rather than recruitment and training policy

    it’s still a chilling thought.

    and I suspect, watching the video, that the same thinking still permeates: that soldiers will be conscripted and thrown into the meat grinder to panic when they encounter a fire fight or put another way, lead and conscripts are available cheaper than good selection and good training.

    On a brighter note, I do think that a handy, light rifle with low recoil, flat trajectory and an emergency full auto capability – like the M16, was a good decision.

    • That is where I think the British Army did the right thing for many decades with its infantrymen — training them to put the emphasis on effective, well-placed shots with rifles like the 0.303″ Lee-Enfield and L1A1 SLR. This philosophy even extended to the Royal Armoured Corps, as witness operation of the Rarden 30mm cannon on the Scimitar AFV and Fox armoured car ; instead of using a high-speed belt feed like most contemporary weapons in other armies, the Rarden uses a hand-held 3-round clip, the emphasis being put on extreme accuracy from a well-made gun, accurate shooting from a well-trained crew, and devastatingly effective ammunition design.

    • Keith, the “attitude” is based on experience. Everybody misses in combat. SLA Marshall wrote stuff about this (chiefly in Men Against Fire) that is still widely accepted by combat vets today, even after Hackworth (a guy who had his own credibility issues) exposed Marshall’s “data” as, essentially, academic fraud and all-but-nonexistent.

      We do know a few things that work. Drill, drill, drill in the principles and practices of aimed fire, and stress inoculation so that you can still run your drills when your heart rate has gone from 72 (usual walking around) to 145 or so in about a second — that’s something that can’t really be replicated, even with the well-thought-out measures used on Buckner Range here.

      While current SOF uses aimed fire on rapid-acquisition sights (Aimpoint or EOTech, basically) even at point-blank, the Vietnam-era unaimed, pointed fire then called quick kill is also acceptable for short range. If you drill in hipshooting you can hit the man-sized E silhouette consistently at 100-150m from the hip. It’s out of favor now.

  12. A few comments on this.

    1.They were very forward looking, but they saw dimly. Today’s weapons aren’t what they envisioned at all, and tomorrow’s go in different directions entirely.

    2. Interesting to see that the Colt had an ACOG and one entry (AAI?) had what looks like the Elcan M145.

    3. An instrumented test range is reasonably constructible. So would be a moving target range, based on the practices here. Computer control is far more advanced. So is data collection (look at the stuff than National Instruments or Venturi makes available for high school physics classes, even). One thing the moving targets on this range don’t do, that real pop-up-shoot-back targets do do, is change direction erratically, and another is move forward and back — towards you and away. A 75 meter target that will be a 10 meter target in a minute in a series of 4-5 second rushes between covered positions — at night — would be a realistic one.

    If you did it right, the use of the range for competition and practice (4-day weekends?) would pay for its testing use during the remaining days.

    • Very good ideas for an automated test range, Kevin. A combination of multiple assymetrical trackways ( to simulate moving targets going in different directions ), random computer programming ( to simulate erratic course changes as on a real battlefield ) and multiple pop-ups ( to simulate unexpected opposing forces appearing in different areas of the battlefield ) might just be the ticket. It probably won’t be cheap, but with careful planning, there is no reason it would be excessively expensive either. A properly-integrated modular design approach could result in a very cost-effective battlefield firing range that lends itself to easy modifications and upgrades to meet changing needs.

  13. This is very unique opportunity to communicate ideas of interest and I wish to give my thanks to all who added to (or corrected) my knowledge. This is really great forum!

    Just a couple of final thoughts on my part.

    1) The G11 is a phenomenal piece of work and I would not venture to call it ‘failure’ in convetional sense of the word. But, I also spoke to a man who was able to see it in action. His take was: “once dismalteled it looks like dog’s breakfest” and “to replace magazine is awkward, at least”. Since I first have read about that venture sometimes around 1970, I kept keen interest in it.

    2) Most of what comes to public awarness as ‘new projects’ is driven top-down, from desks of procurement bureaucracy, very rarely on request from grunts. Just as so aptly said in one video by Mr. Jim Sullivan; “…those guys do not care what soldier has do fight with, they care for their warm spot”. In that category belongs LSAT as well; it will be rendered useless.

    3) I believe something is still possible before we throw towell in the ring. Personally, I can see new casing material as a possibility. Also, the pottential of multiple shot was not fully materialized yet. I do gather, that there are many factors in play in background, but some compromise can be and should be entered.

  14. There is a speculative article from about the year 2000, drawing on discussion of using plastic cases and Becker/Oerlikon advance primer ignition blowback actions from 1990 onwards, over on the Gunwriters connect page.

    It might be of some interest.

    There is some good info over there – unfortunately I only discovered that site after Peter Kekkenon, the main author, had passed away.

  15. It’s too bad the G11 project got canned, it’d be interesting to see how it would’ve progressed.

  16. As mentioned the G11’s main fault was heat build up. During testing there were more than a few KB’s due to overheating of the gun. The ammo also had issues with anything but delicate handeling and storing. It was prone to breaking and cracking.

    There is a .PPT out there showing all the failures of the G11 that was made by one of the higher ups of HK.

  17. I just watched the video, and noticed very strange trigger manipulation by the soldier who fired AAI rifle. To my inexperienced eye it looks like either rifle refused to fire every other time, or he checked dead pull every time (seems unlikely), or the rifle had some kind of trigger safety that demanded a full pull before each shot. Also, when he pulled the trigger back before shots, every time a click was heard – maybe the salvo assembly had to be re-set with the trigger to ready it?

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