Walter Perrine’s Pirahha Pistol

Earlier this year American Handgunner ran a story about Walter Perrine’s interesting Pirahha Pistol. The pistol’s operating mechanism (Patent #3861274. Issued Jan 2, 1975) bears a striking resemblance to the KRISS Vector submachine gun/carbine. The blowback-operated bolt is connected by a linkage to a mass that actuates downward in the pistol grip, deflecting some of the recoil in a downward direction. The KRISS has a similar system although the bolt is connected to a mass that sits forward of the pistol grip, rather than in it.

According to American Handgunner, between 1969 and 1975 just 23 Pirahha pistols were producued.

[ Many thanks to Rufus for emailing me the info. ]

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.


  • snmp

    You could found same idea in older weapon like the French SMG MAS 38 Or many small bore Russian olympic pistol


  • “The blowback-operated bolt is connected by a linkage to a mass that actuates downward in the pistol grip, deflecting some of the recoil in a downward direction.”

    We went through this argument with the Kriss – recoil can’t be “deflected”, it’s a physical impossibility. Remember “equal and opposite reaction”? The bullet and gun gas go forwards, so the gun goes backwards. End of story…

    • Tony, heh, yes I remember now. For most people, recoil is the perceived force (speed and energy) and direction that the gun moves in after being fired. Changing either the force, for example muzzle brake or fancy recoil dampening stocks, or direction (fancy bolts/carriers, muzzle porting, inline stocks etc), would be considered changing recoil.

  • Spiff

    Is there a firearms test report on this pistol? What caliber(s) were available?…
    Other then moving the cocking handle to the top of the receiver (ala MAC 10), and maybe having select fire capability…could be interesting…

  • Thomas

    Another reason (or so it sems to me) that the kriss has a better recoil is that the barrel ist lower on the frame … It pushes the the hand back. When the barrel is positioned over the hand, the forces pushed the wrist up in th usual recoil movement. Have nobody else notised that or is it just me ? I find it obvious. Of course the the way it’s build also has somethin to do with it ;c)

  • greg

    I wonder how similar the mechanism in the grip is to the one that is in the grip of the Skorpion machine pistol?

  • zincorium

    Looks interesting, somewhere between a broomhandle mauser and a TEC-9. Unfortunately it didn’t have the internet and all the modern gun media to sell it.

  • howlingcoyote

    What cartridges was it chambered in?
    What is the collectors value today?

  • Thomas – yes, the central location of the Kriss’s barrel was identified as a reducer of “muzzle flip” in the thread on this gun – there was a Russian .22 rapid-fire target pistol which used a similar system in the 1960s before being banned from the Olympics.

    Steve – a muzzle brake certainly does reduce recoil, which is why I specified that if “the bullet and gun gas go forwards…”

    Gun actions can spread out the recoil force over a longer period, changing it from a sharp kick to a long push, but the total force remains the same – and it can’t be “deflected” (except of course by a compensator – which is a form of muzzle brake).

    Increasing the gun weight has a similar effect – if the gun is doubled in weight, it will recoil at half the speed. The total recoil force remains the same, although the recoil energy is reduced.

    The only way I can think of to reduce the recoil force of a conventional gun (leaving aside muzzle brakes etc) would be to convert some of it into another form of energy. For instance, if the bolt movement was used to generate electricity which could then be stored. However, I don’t know that anyone has tried this – and the efficiency would be low, anyway, which would limit the recoil reduction.

    • Tony, heh, I was just thinking about the bolt energy idea yesterday when reading a powered rail patent 🙂

  • Hrachya Hayrapetyan

    Recoil exist ! 🙂 But it’s being redirected downwards…so not the recoil is eliminated , but FELT recoil. It just doesn’t hit your shoulder, but goes down. Also downward motion of recoiling mass acts like a muzzle brake (muzzle tries to jump the gun up, downward going mass tries to do the opposite).
    So we can’t eliminate the recoil ! but we try to make it be FELT softer …or in ideal world make it zero ! 🙂

  • Hrachya Hayrapetyan

    greg, I guess in case of Skorpion the mechanism in the pistol grip is made to either delay the bolt or reduce the rate of fire … or both .

  • Hrachya Hayrapetyan

    Anyway this system is better than one in Kriss Super V , because it makes the gun much more compact (or you’ll have longer barrel at same overall lenght) !!
    I think if one of major firearm manufacturers make this gun adding better exterior design (just for looking cool), a lot of rails 🙂 and some other improvements, then it could compete with Kriss and even gain a nice part from SMG/PDW market pie.

  • Bryan S

    You also have energy being channeled down, aka, the momentum of the bolt.

  • American Handgunner had previously published an article about the Piranha during the mid-1980s. Besides US Patent #3,861,274, Perrine was awarded numerous other patents revolving around the same basic concept: 3,630,119; 3,661,049; 3,709,091; 3,732,779; 3,748,961; 3,783,739; 4,126,079; 4,183,282; 4,467,698; 4,719,841; 5,517,896; and 5,517,897.


  • Roy

    I’m frankly very disappointed. I expected this gun to shoot piranhas.

  • El Duderino

    Roy — you’re going to have to check out Despicable Me for that one.

  • Airrider

    Hey, hey, hey: El Duderino, you’re forgetting the REAL weapon there: the Squid Launcher.

  • Airrider, you’re right. It certainly seems bizarre to attack submarines by firing giant cephalopods at them…