AAI 2nd Gen SPIW Flechette Rifles

The SPIW program began in 1962 with entries from Colt, Springfield, AAI, and Winchester. The first set of trials were a complete failure, and both Colt and Winchester abandoned the project at that point. AAI pressed on, producing these second generation rifles – one for trials in 1966 and one after. Both are chambered for the XM-645 5.6x57mm single-flechette cartridge. Under testing, both showed multiple serious problems in reliability, noise, cook-offs, and accuracy. The company would struggle on for years continuing to develop the flechette rifle system, but would be ultimately unsuccessful.

Thanks to the Rock Island Arsenal Museum for allowing me access to film this very interesting rifle! If you are in the Quad Cities in Illinois or Iowa, the Museum is definitely worth a visit. They have a great number of small arms on display as well as an excellent history of the Rock Island Arsenal.


  1. A most harrowing experience for those on the receiving end of the bad results, especially if someone makes the “h” silent in “harrowing.” I don’t like the taste of arrows in the morning, or at anytime of day. It’s not like the project was going to succeed anyway, as conventional means of putting holes through victims are much cheaper and less likely to put powdered synthetic materials into your lungs. Okay, I will admit that sabot shot works with tanks and artillery, just not with your rifle!

  2. Blank-firing replicas of those guns would look seriously classy in your next sci fi movie. (Let’s see, what else can you say about them? Uh….)

  3. The whole SPIW program just goes to show how unserious and entirely delusional the US small arms development community really was, back then, and to a degree, how delusional it still is.

    Here’s why I say that: Nobody at that time, or any other, really articulated what the hell it was they expected these weapons to do, in an integrated fashion with tactics and operational art.

    Look at those things: Can you imagine hauling them around the battlefield, jumping out of helicopters or vehicles, clearing buildings…? Any of that? The weight is good, but the unwieldy nature of the whole SPIW program, with it’s attached or built-in 40mm semi-auto grenade launcher? Dear God, the head just hurts, thinking about it.

    And, Ian didn’t mention something with all that, either–The reason these two prototypes are so light is that there was still that 40mm semi-auto grenade launcher to consider. They had to be light, and the question might be asked about how that would affect the longevity and ease of control on full-auto for the flechette-firing component.

    The other issues with the flechettes come to mind–You’ve got a serious question as to lethality for this idea, especially as far as the single-flechette concept goes. Unless you manage to hit a bone, the tendency is to have them zip through and not really have much in the way of effect on the target.

    Acquaintance of mine used to love to experiment with exotic cartridges, and he went so far as to actually hunt with them. The duplex rounds he worked up seemed to have decent effect, but the flechette ones? If he hit anything, the deer just bounded off like nothing happened, and he had a hell of a time tracking them if he’d hit them. Granted, he was working with a .410 shotgun shell and home-machined sabots around his flechettes, but the results weren’t that inaccurate, and his velocities were not that far off the SPIW spec. His contention became that flechettes are simply not as lethal as bullets unless you hit something that deflects the things. He never got the “hooking” effect that the SPIW proponents said you would.

    You set out to design a world-changing small arms system, you’d better have a good idea of how to fight with it. I’m not sure that the SPIW guys ever even considered that question, because it goes well beyond the simple question of how the weapon operates on the range or in the laboratory. As well, if you’re going to try to put cutting-edge experimental technology into something you’re going to issue, there are two principles you need to follow: One, it needs to actually work, and two, you need to know how to take advantage of it, both tactically and operationally. The SPIW program lacked both of those guiding principles, and the point of the whole thing soon became highly questionable because you could meet the actual tactical and operational needs with the much cheaper and actually functional M16/M203 combination. SPIW wasn’t just a bridge too far, it was an entire series of them, leading nowhere.

    What’s interesting to note is the longevity of the concept; SPIW became OICW, and the whole OICW thing foundered on the same set of issues, with some new ones added in once they figured out that 40mm was too big to integrate as the indirect portion of it all.

    Which goes to a thesis I’ve developed that no really bad idea in weaponry will really go away until it has demonstrably failed, killed off thousands of our own troops, and then become a “well-known impossibility” that no one will ever try again. At which point, the enabling technologies will be developed, and nobody will ever take advantage of them to make something like SPIW or OICW work, because “discredited in the conventional wisdom”.

    There’s also the “blue sky” problem, in that the idiots in the American small arms procurement system keep going for the ultimate, end-all, never to be purchased ever again solutions, instead of going “Hey, let’s incrementally improve things based on the current state of the art…”. They are in love with the “game-changing” “paradigm-shifting”, and never bother to look at the idea of gradually evolving existing technologies to make better weapons that are more durable, effective, and more affordable.

    If they’d have done that with the M16, continuing past the point where the crisis-mandated fixes were done, we’d be looking at a weapon that looked the same, yet was nothing like the originals. There’d be stainless steel parts in the bolt carrier, better coatings, improved cold hammer-forged barrels with longer lives, and a whole host of other things that have been neglected. People don’t realize it, but the M16A2 and M4 have legacy Technical Data Packages that preclude doing any of these improvements, most of which would have no impact whatsoever on the needs of interchangeability and fitment. The reason that the Canadians have dominated the export market for the M16 has little to do with Colt USA, and everything to do with those damn barrels–Diemaco invested in what was then the only cold hammer-forging equipment on the North American continent, and accrued all the benefits. FN wanted to go to the same sort of barrel they put on the M249 or M240, which are CHF, but they were told “No, build the TDP…”. Part of the problem with the early FN rifles was that they tried doing the button-broached rifling in-house, and didn’t have the expertise with it that they needed, so they were producing sh*t barrels for awhile. Rumors told me they sub-contracted, or figured it out for the later ones.

    What’s interesting about that? There was a guy producing sniper and match rifles for small-scale customers, and he was using the same barrel blanks that FN was building for the M240–All he did was machine them down. The MG barrels were that accurate.

    • “Which goes to a thesis I’ve developed that no really bad idea in weaponry will really go away until it has demonstrably failed, killed off thousands of our own troops, and then become a “well-known impossibility” that no one will ever try again. At which point, the enabling technologies will be developed, and nobody will ever take advantage of them to make something like SPIW or OICW work, because “discredited in the conventional wisdom”.”

      I would say there’s a caveat needed in your thesis, that “demonstrably” should be changed to “supposedly.” There have been more than a few instances where weaponry was wrongfully blamed, or blamed for the wrong reasons, and went on to color development. Opposite side of the same coin, so maybe it’s a corollary; inventor’s optimism and bureaucratic inertia both keep bad ideas alive longer than they should be, and unfounded skepticism & simple politics kills many good ideas. In short, centralized product development is inherently irrational.

    • “(…)flechettes(…)”
      Soviets also tested prototype flechette systems in 1960s namely АО-27 (fire-arm) + ОПС (cartridges).
      As development T-12 Rapira (100 mm smooth-bored towed anti-tank gun) ended in success it give motivation to test feasibility of using similar projectile (dart with sabot) in small arm system, thus this one was developed. Following tests revealed that АО-27 has milder recoil than then current issue 7,62×39 weapons, smaller spread than AK, and projectile have flatter trajectory not only than 7,62×39 but also 7,62×54 R however lack of knock-power was noticed together with excessive price of cartridge used, so it remains only prototype.

      “(…)He never got the “hooking” effect that the SPIW proponents said you would.(…)”
      This problem was noticed during АО-27 trials, some time later Dvoryaninov developed special dart to solve this, see middle part of image:
      notice cut into middle, which caused it to break apart after hitting targets.

      Interestingly, no special weapons were developed – instead re-barreled SVD and PK were used, with first firing tests in 1973, see 2nd photo from top here:
      this allowed better comparison of cartridge vs cartridge rather than system (weapon + cartridge) vs system. Results were great with much more frequent hit scores during tests.
      Although following tests confirmed that such cartridge provide greater chance of scoring hit, Zeitgeist in Soviet Union (1980s) was against it and… there was not pressure to field such system as NATO members did not have and did not planned introduction of anything similar. Finally, decision was to invest into development of optimal ballistic 6-mm cartridge of classic design, which would finally become 6 x 49 and… never got into service due to Fall of Soviet Union.

    • This explains some of the Ordnance Department hate for Project Salvo, which originated with the Infantry School and culminated in the M16. So we have a program that started outside the Ordnance Department and adopted a commercial weapon completely outside of the arsenal system. While the SPIW was a continuation of some aspects of Salvo it became a typical overcomplicated mess in keeping with M14 era Ordnance Department performance.

    • “(…)longevity of the concept; SPIW became OICW(…)”
      And do not forget about off-springs, namely
      PAPOP (France, 1990s) combining 5,56×45 mm NATO cartridge with grenade launcher with fuse-time-setting ability (calibers 25 mm 30 mm and 35 mm considered). Ended at mock-up stage, as it was concluded that such weapon would be too heavy. (I am wondering how many time they needed for finding that, nonetheless it seems to take less that in U.S. case)

      K11 (South Korea, 2000s) combining 5,56×45 mm NATO cartridge and 20 mm, produced since in 2010, but apparently it has so serious problems production was halted until solution was developed

      80.002 (Soviet Union, 1970s) combining 5,45×39 mm cartridge and 12,7 mm grenade, see photos: http://www.dogswar.ru/oryjeinaia-ekzotika/strelkovoe-oryjie/3952-dvystvolnyi-avtomat-.html
      Grenade launcher was self-loading and feed from detachable magazine of capacity 10. There was one common return spring for automatic rifle and grenade launcher. Beyond using built-in grenade launcher, possibility of firing rifle grenades sticked on muzzle device of 5,45 mm part was provided. It was in development until early 1990s.

    • “(…)duplex rounds he worked up seemed to have decent effect(…)”
      It basically acts like 2 hits very near each other (both in terms of space and time) of “normal” cartridge, so it is not surprising.
      It is worth noting that this is very old concept, reappearing from time to time, one example might be (strictly speaking triplex) made by Greener in 1920s:
      Soviet Air Forces actually used duplex cartridge, namely in quad-barrel 12,7-mm machine gun used in Mi-24D. See chapter Double bullet cartridges 12.7 1SL (9-A-4012) and 12.7 1SLT (9-A-4427) here http://gunrf.ru/rg_patron_12_7x107_eng.html note dimples into case holding second bullets.

    • True enough. Yet what explains the fate of the 5.56mm LSAT project?

      There you have an US Army development program that actually succeeded, and it could make a real world improvement in the effectiveness of an infantry squad, yet the US Army refuses to proceed any further towards fielding that LMG. And the reason the US Army provides for such an inexplicable choice seems to be that the improvement isn’t great enough for them.

      • The 5.56mm LSAT was a technology exploration program, exploring the MECHANISM, while exactly duplicating the ballistics of the M855 round from the M16, M4, and M249 — even using M855 projos. That way, when looking at performance, weight, cost, etc. of the new system, a direct comparison could be made against known quantities that had IDENTICAL performance down range, so evaluators weren’t misled by differences caused by using different size projectiles or different ballistic performance. There was NEVER an intention to field it in 5.56mm.

        As I understand it, the current spiral is to decide what the optimum projectile and ballistics are, and scale the mechanism to that, and then see if that is still feasible.

    • “(…)idiots in the American small arms procurement system keep going for the ultimate, end-all, never to be purchased ever again solutions(…)in love with the “game-changing” “paradigm-shifting”, and never bother to look at the idea of gradually evolving existing technologies to make better weapons that are more durable, effective, and more affordable.”
      Keep calm, during Cold War it was not limited to small arms: once upon a time Soviets pursued idea of variable geometry wings and decided that Su-7 should be used for starting point as it has high requirements regarding landing strips, which is undesirable in front fighter, so they rebuild one and then exposed them to public and…
      Western observers concluded it was strictly a trials machine, on the belief that the Soviets would prefer a “clean sheet” design over recycling the obsolescent Su-7. That was underestimating the Soviet willingness to make the most of existing technology, as opposed to the American instinct of wanting to come up with the latest whizzy thing.

  4. When Ian was going over these weapons in the Museum (I’m attached to the Arsenal and arranged the visit), we discussed those operational concerns a bit, and the fact that the 40 mm grenade launcher was a bust, all the way around. The weapons themselves handle very nicely — your favorite deer rifle minus 2.5 pounds. The SPIW program eventually made the grenade launcher optional — it could snap on or off and hence you could give it to the big guy in the squad, or carry it as a piece of kit and use it only when needed. There’s also the fact that these are prototypes. The fielded weapon would have undergone improvements if the design had been adopted.

    I’m an accuracy guy and I’m not certain I’d have been very enthused about the SPIW program in general, and with the idea being “let’s put more metal in the air” instead of “let’s train better marksmen.” But these designs show that everything was on the table in the ’50s and ’60s, and all or most options were being examined.

    A big thanks to Ian for doing this piece and promoting the Rock Island Arsenal Museum. It’s a great place to visit for small arms history enthusiasts.

    • Let me second or third the RIA museum recommendations – it is a national treasure.

      Extremely impressive collection of US and foreign firearms. Viewing conditions can be tough, but the history is unmatched.

  5. Regarding the odd behavior of fin-stabilized flechettes, they act remarkably like longbow arrows or crossbow bolts in flight;


    As Tod Cutler begins explaining at 10:10, concerning the “swallowtail” broadhead, the combination of the beveled tip of the AAI flechette with its relatively small vanes may have caused the tip to actually have enough aerodynamic effect to cause the flechette to veer off course. This might at least partially explain the SPIW’s accuracy problems.



  6. >“game-changing”, “paradigm-shifting”

    Even non-English speaking countries are invaded by those terms to make marketing and Human Resources more “trendy”…

  7. As much as these and other prototype “game changing” rifles may be subject to criticism, one thing is clear: the U.S. can afford to play with these fancy ideas because of its sheer wealth, at least as presented in its billowing military budgets. And if there is shortfall, more money can be printed as is being done more than century.

    Mainly – it serves two purposes: first it proves where are limits to achievable and secondly it benefits to potential opponents who will stay clear of duplicating it. So at the end it is “win-win” if you do not mind slightly sarcastic tone.

    • It’s the same dilemma faced by the previous global hegemon, the British Navy. If it tried out radical new ideas that succeeded, then it simply obsoleted its own gigantic fleet while rival navies would throw everything behind their own copies. If it tried out radical new ideas that failed (there were many), then everyone knew these were dead ends. You go first, sir.

  8. The primer actuated bolt system is surprisingly compact and basically simple in design. Of course, the downside is a much more complicated cartridge. But I am very much impressed by this smart solution.
    On a side note, as a non-English speaking person I was delighted to at last hear how SPIW is pronounced.

  9. USA: SPIW
    France: PAPOP

    Primer-actuated mechanism: Nice tribute to John Cantius Garand’s first prototype design… (or NOT?!)

    bayonet lug requirement=ROFLMAO!

    Thanks to all respondents… There’s a lot to study and contemplate and research from all the responses!
    Thanks for allowing Ian to demonstrate these crazy would-be-killer contraptions to us at Forgotten Weapons! (New category? Forgotten–and rightly so?–weapons?)

  10. Given a cringe-worthy horrible scenario where we have a hypothetical Vietnam War-era US Army infantry squad (all armed with the SPIW and nothing else except M1911’s and trench knives) square off against two ragged and unshaven platoons of Imperial Japanese holdouts armed with Type 38 bolt-action rifles with bayonets fixed (with “second rate” side arms like the Type 94 Nambu pistol, perhaps some have imported Ruby pistols, and one with a long-barreled Zulaica Royal), who’s going to win? Will the “Space boys” riddle the old men full of flechettes, or will the old-timers’ fighting spirit carry them to victory? Find out next time on “NOT INVENTED HERE!!”

    Yes, for those asking, this is a total joke.

    • It literally depends on the range.

      If we’re talking WW1 trench warfare range (which could also be called “NVA sappers assaulting Special Forces or Marine firebase” range), the sheer volume of fire of the SPIWs should have the same effect as massed shotgun or SMG fire, which tends to win such engagements through sheer target area saturation. Individual accuracy would be less critical than literally filling the air with projectiles, as Project SALVO concluded.

      However, if the range is more the Afghan War (any version) sort, you’d be better off with the old bolt-action. At ranges beyond about 200 meters, aimed fire will count for more than volume of “covering fire”.

      It’s worth noting that the M-16 was supposed to do both jobs, volume of fire at under 100 meters on full-auto, aimed fire out to 300 meters on single-shot. The fact that it failed at both is less of a commentary on its design than its implementation.

      And yes, the M193 round should have been an effective man-killer even at 300 meters, if it didn’t gum up the workings so thoroughly. Out to 500 meters as the Army claimed, not so much. (Varmint hunters normally restrict the use of the .223 round to ranges under 250 yards/228m.)

      NB; My preferred weapon for such combat situations is an M1918 BAR in .30-06.



      • Speaking of good design, your better choices include the Colt R75A and the FN Model D, both of which had better ergonomics and had been designed from the get-go as light machine guns.

        Now if the holdouts were camping a hilltop and had access to something like huge rocks or even a few aircraft-mounted 100 kilogram bombs (taken from a crashed Ki-43 in an old war comic I read), no amount of rifle-fire would stop the incoming heavy objects, and especially not the bomb bouncing downhill! Anyone dumb enough to shoot the bomb after it’s thrown is not coming back with intact clothes. Just kidding…

        • They’d be fools to try it. One nasty characteristic of Japanese iron bonbs was that most of their impact fuzes had one or more “dead” angles, which meant that on a glancing impact, they wouldn’t fire.

          However, if disturbed after that, they would unfailingly go off. Right in your face.

          There’s a reason U.S. EOD procedure for IJN UXBs was always “blow it in place”.



          • Which set of fools are we describing, the fools throwing the bomb downhill or the fools shooting the bomb with SPIW rounds? Or perhaps both?

    • “(…)hypothetical Vietnam War-era US Army infantry squad (all armed with the SPIW and nothing else except M1911’s and trench knives)(…)two ragged and unshaven platoons of Imperial Japanese holdouts(…)”
      I would say other equipment (not arms) and ability (or lack) to exploit advantages it give would decide outcome. Take for example AN/PVS-4 which give boost for effectiveness for team No. 1 during night fighting. Also having radio-receivers like AN / PRR-9
      grants ability to command without need to yelling/whistling/flare, though it must be keeping in mind that there is having and leveraging it against enemy.

      • Speaking of such, we should also factor human element into the equation. If team 1 is pretty good at keeping up good strategy, squad morale, and interpersonal communication, the chances of survival (even with wonky and potentially unreliable “space guns”) are better than if the team is uncooperative to the point of intentional friendly fire during the battle. You can’t go fight the other team if your squad mates aren’t working together as a team!

  11. If you come on the island check out artillery park as well. And the unrestored M4 from the Battle of the Bulge. There very few WW2 tanks the saw combat left in the world

  12. This rifle looks like an M1 made love to a Johnson. Was this perhaps done on purpose to please the people in charge of the program probably the same people who preferred the M14 TO THE M16

  13. when you go to the Rock Island Arsenal again you need to do a video on the Atomic Annie canon that is there.

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