Rock Island Auctioning Off Experimental Project SALVO M1 Garand .22 Cal Duplex Rifle

MNH26-R-F2-L

Up for auction through Rock Island Auction Company is a rifle that is very significant to the history of the military .22 caliber rifle cartridge. Below are pictures of the rifle, an experimental M1 Garand chambered for the .22-06 Duplex caliber which was a part of the SALVO II test conducted in December of 1957:

 

MNH26-R-F2-L

The rifle has tape on both the stock and forend, most likely to identify it as being in a non-standard caliber. Image source: rockislandauction.com

 

MNH26-R-F1-L

Image source: rockislandauction.com

 

 

MNH26-S-CU22-L

The business end of the .22-caliber Garand. This rifle would fire two projectiles per shot. Image source: rockislandauction.com

 

Pages 13-16 of SPIW: The Deadliest Weapon That Never Was provide some background on the SALVO II test:

Regarding ORO’s “long-necked” Duplex and Triplex .30 M2 loadings, the results were extremely encouraging. These further studies substantiated the Hitchman report’s findings that bullets fired in a simultaneous salvo are independently potentially lethal, and therefore for each shot fired a sum of lethal probabilities existed, which increased the statistical kill probability dramatically over that of single-bullet firings. Indeed, ORO reported in the SALVO I results that .30 Duplex cartridges showed a 65% increase in kill probability over standard (Simplex) rounds. The Triplex loading produced a double hit rate of single bullets; further tests might even prove them superior to the Duplex loads.


Improvements made as a result of the SALVO I field test led to a further series of trials at Fort Benning in December, 1957. Dubbed naturally SALVO II, they sought to gather more meaningful data on measured hit probabilities. The end result was the first-ever true comparison of ammunition effectiveness under conditions realistically simulating actual combat. ORO found that the accuracy of aimed fired changed when variances in range, target exposure time, and degree of marksmanship skill were introduced. These fluctuations were painstakingly added to the basic equation, with the aid of the innovative ORO measuring techniques already in place for the hit probability studies.

In sum, SALVO II confirmed to the ORO analysts that the target exposure time and the actual area presented by the target were the determining hit-probability factors. Target movement and degree of incoming enemy fire were the variables next in importance. On the ammunition side, the usefulness of ORO’s new standard-length-case Duplex concept was further borne out, and it was at this point that ORO recommended a 7.62x51mm version be perfected and adopted as standard for combat use. In the face of the Army’s hallowed marksmnship tradition, ORO stated flatly that accuracy requirements for any new shoulder rifle should be based on an intentional, built-in aiming error of three mils.

To the SALVO teams, there was now no question as to the effectiveness of multiple projectiles being delivered with each trigger pull. As noted, ORO had devicsed the Duplex bullet in the 7.62mm NATO case as the most expedient method of adopting this controlled dispersion theory. Soon, however, ORO switched allegiance to even more exciting and dramatic advances in hit probability, by marrying BRL’s concept of high velocity and consequent flat trajectory to the almost imperceptibly low recoil impulse of a lightweight, single flechette. ORO recommended that by following this path, a controlled-dispersion burst weapon could become a reality for every American combat soldier. This new weapon would be devastatingly lethal, regardless of his individual marksmanship abilities.

 

The .22-06, more properly called “Cal .22/30” was a powerful round for its caliber, utilizing the .30-06 Springfield cartridge as its base. It fired two 50-grain bullets at 2,975 ft/s (first bullet) and 2,897 ft/s (second bullet), for a combined muzzle energy of just under 2,600 Joules:

SAL2

The calibers of the SALVO II test: From left to right, Cal .30 Ball M2, Cal .30 short neck Triplex, Cal .30 short neck Duplex, Cal .22/.30 short-necked Simplex, Cal .22/30 long-necked Duplex, AAI flechette shotshell. Image source: Ray Meketa, from forums.gunboards.com.

Six years ago, in 2009, another .22-06 Duplex SALVO rifle came up for auction through Gun Auction, and sold for just over $2,000. The rifle up for auction this time is expected to go for between $6,500 and $9,500, but maybe for one member of our audience such a price is worth owning such a significant piece of US small arms history!

 

Thanks to Daniel for the tip.



Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


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  • Julio

    “target exposure time and the actual area presented by the target were the determining hit-probability factors. Target movement and degree of incoming enemy fire were the variables next in importance.” Don’t you just love research: it tells you so much you already knew! Seriously, an interesting piece.

    I don’t get this bit, though: “.30 Duplex cartridges showed a 65% increase in kill probability over standard (Simplex) rounds. The Triplex loading produced a double hit rate (= 100%?) of single bullets; further tests might even prove them superior to the Duplex loads (how is it doubtful that 100% is superior to 65%? or is it that an “increase in kill probability” is a long way from being the same thing as a “hit rate”. Apples and oranges, I guess.).”

    • tts

      “how is it doubtful that 100% is superior to 65%?”

      Hit rate is only 1 of several factors that go into deciding which cartridge would be superior. Cost, weight, barrel wear, recoil, cartridge durability, lethality, etc. all have to be considered too.

      I believe the duplex, triplex, and flechette cartridges were all abandoned eventually after being found unsatisfactory for one reason or another but I don’t know the details.

      • lucusloc

        Penetration and lethality compared to larger single projectiles maybe?

      • Duplex was not abandoned; the 7.62mm Duplex round was fielded as the M198.

    • MPWS

      You can tell that author of this text was not scientist/ technician, but journalist/ salesman. They have notorious preponderance to distortion, no matter what the subject is.
      BTW – it also stopped me in my sensory tracks.

  • Blake

    really cool article, thanks

  • Tassiebush

    It’d be interesting to see the duplex round concept introduced for pest control. A cheap bolt action firing .22-06 or .22-08 duplex or triplex might be quite cost effective.

  • Brody

    I like the dublex concept if applied to a weapon like the 249.

    • David BB

      I am given to understand that the 1960s XM198 duplex round in 7.62x51mm was intended for the M60 LMG, to increase the density of fire within the beaten zone. However I do not think it was ever widely issued, and to the best of my knowledge is not currently manufactured.

      From what I read in various places on the Internet, the bullet loaded in front was intended to fly to point of aim, and the rear bullet would normally be somewhere within 2-3 mils of it. This is not too far different from the normal dispersion of a belt-fed MG fired from a tripod or pintle mount anyway–typically the dispersion in six-round bursts is around three mils.

  • Zebra Dun

    Throw three rocks at a target, odds are good one rock will strike, 50/50 for two rocks and rarely will three rocks hit the target. Three rocks on target create instant kill, two give good knock down, one rock leave blood trail.
    >Neanderthal Rifle Range coach<

  • MPWS

    I have long term interest in this subject with single-minded objective – increased hit probability. As a result I have continued my own limited research and conceptualised shots with 2, 3 and sub-caliber projectiles; with identical casing – all and each for specific application.

    Thus MPWS (Multiple Projectile Weapon System)

    If any person or organization has interest to work with me, please leave note with Ed.

    I believe this project should be revived, if perhaps in a new form.

  • dan citizen

    “ORO stated flatly that accuracy requirements for any new shoulder rifle should be based on an intentional, built-in aiming error of three mils”

    Clunky sentence, makes it sound like they want more MOAs

    • They did.

      • dan citizen

        Neat. Could you elaborate on their reasoning? (if anyone knows, I’m guessing you do).

        • Project ALCLAD (the ORO project to improve body armor) requisitioned the creation of the Hitchman report, which analyzed three million casualties and found that the location of hits was equally random for both bullet strikes and fragments from explosives. Essentially, the old theory of marksmanship didn’t hold up under closer examination. Therefore, it was reasoned, to actually improve hit probability multiple projectiles could be launched at once with a certain amount of dispersion, possibly causing what would be a near-miss to become a hit.

          And, anyway, if hits are essentially random, precision accuracy is not necessary. That reasoning, however, has been changing since 2003.

          • dan citizen

            Neat! I knew you’d have a real answer.

  • DetroitMan

    “In the face of the Army’s hallowed marksmnship tradition, ORO stated flatly that accuracy requirements for any new shoulder rifle should be based on an intentional, built-in aiming error of three mils.”

    So how big was the dispersion pattern of the duplex and triplex ammunition? Was it enough to cover three mils of error?

  • James

    Where’s forgotten weapons? Why aren’t they covering this!? Quickly brothers, we must summon the elder God of elder weapons!

    IAN! IAN! GARANDU FHTAGN!

    (I tease. An excellent article.)

  • dan citizen

    If I bought this I would make it so damned tactical!

    Tapco folding stock, 9 picatinny rails, red dot, ACOG, BUFS, lasers (red and green).

    And I’d chop that barrel down to 16″