Hank Takes Strange to the Range: The Bushmaster Arm-Pistol with Hank Strange

Since the beginning of the modern era, the question of how to arm the increasingly large body of non-infantry troops has become both more pressing and more difficult to solve. Initially, these men could be armed with pistols, or perhaps submachine guns firing pistol calibers, but as the Cold War entered its third decade, an additional complication was added to the problem: Body armor. Enemy troops – especially encircling paratroops – equipped with body armor could potentially make already lackluster pistols and submachine guns almost useless in a serious skirmish. Weapons were (and still are) needed that could defeat body armor while providing enough firepower to repel an assault, yet still be small and light enough to be carried by troops whose primary mission did not involve pulling a trigger.


The Colt IMP-221, AKA the “Davis Gun”, showing its ability for the receiver and magazine housing to rotate out of the way of the firer’s arm. This weapon was intended to be fired with the arm extended, like a pistol, and was designed to give aircrews and other personnel the firepower of an infantry rifle at short ranges. Image source: all4shooters.com


The United States Air Force faced a similar problem in how to arm its aircrews. Pilots of downed jets were increasingly vulnerable as enemy forces mopped up the essentially unarmed jet drivers. A better weapon, capable of fully automatic fire and firing more potent ammunition than standard pistol rounds, was requested, and several designs submitted. One of these was the “Davis Gun”, designated by Colt the IMP-221, a pistol-rifle hybrid with a bullpup layout, firing the recently introduced commercial .221 Remington Fireball round. This gun didn’t go anywhere, but the basic concept was copied by Mack Gwinn, an enterprising firearms designer, who produced what he called the “Bushmaster Arm Pistol”. The Arm Pistol changed out the IMP’s .221 Fireball for the standard 5.56x45mm NATO, resulting in a weapon as compact as it was loud.

Hank Strange got the chance to shoot one of these rare firearms recently thanks to Safety Harbor Firearms and Walter Keller; the video is embedded below:

Hank’s video does a very good job illustrating why the Arm Pistol concept didn’t really take off. A weapon with this configuration can be described as a thruster (the muzzle) connected to a swing arm around a pivot (the shooter’s wrist), with a counterweight (the receiver and magazine) on the opposite end. This results in a system that wants to “trebuchet” about the shooter’s wrist, creating massive instability and dramatically increasing the time between shots as the weapon swings wildly about the shooter’s wrist.

Though the Arm Pistol/IMP concept was not successful, Gwinn did use the same basic mechanism in his also-obscure Bushmaster rifle.

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 is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at nathaniel.f@staff.thefirearmblog.com.


  • Giolli Joker

    1-something that could really benefit from a properly used “brace”;
    2-needs more SPAS-12 hook.

  • Dougscamo

    How appropriate….a rescue squad wagon standing by in the background….

  • datimes

    I saw one of these for sale at a gun show Saturday.

    • DataMatters

      They were complete garbage from day 1. So unless you buy it as a curiousity, I think the money could be put to far better use.

    • Gambler X

      i keep going to a small town show and its always there. The price never comes down but in 6-7 years its there every year.

  • Martin M

    I’ve often thought that the only thing need to make this work was a simple wire stock.

    • Badwolf


  • GD Ajax

    These days the B&T TMP should be good enough for aircrews.
    Weapons like this could have benefited by being reworked to for either 5.7×28 or 6.5×25 CBJ.

    • DW

      Then you get a P90 or CBJ instead.

      • JustAHologram

        It could still work in 5.7×28 if the had a mag on each side and a feed selector for when one ran out.

        • GD Ajax

          Or just use 30 round Five Seven magazines.

  • Sunshine_Shooter

    I took strange to the range once…

    • USMC03Vet

      Did you unload and show clear? ( ͡° ͜ʖ ͡°)

  • Gary Kirk

    Reverse gangsta style..

  • gusto

    how is that not an sbr bullpup?

    because the maker said it is a rifle?

    seems awfully easy to shoulder or?

    • DataMatters

      Because the brass ejects straight into your eyeball if you use it that way.

    • iksnilol

      No provision for shouldering (no buttplate) and the fact that it has pistol right there in the name.

  • TechnoTriticale

    The Colt .221 version got a USAF nomenclature of GUU-4/P, for those who want to google it.

    I was living in Windham ME at the time Bushmaster released this thing, and handled one at (as I recall) the factory store. It was clearly impractical, and the sights were basically just decoration.

  • TonysTake ✓ᵛᵉʳᶦᶠᶦᵉᵈ ᵀʳᵘᵐᵖ

    I hope the bad guys always have these! My .38 stubby revolver will win every day!

  • Oldtrader3

    “Recently introduced .221 Fireball”? I shot a grouse in the head with one of these, from a Remington bolt action pistol when I was in the Army in 1962!

    • iksnilol

      Pssst… recently introduced when the arm pistol was first made.

  • Kinda surprised Hank didn’t have a problem with the Deutsche Afrika Korps logos all over everything.

    I wasn’t expecting to see them trying to fire it like a straight up pistol– with a basic two handed firing grip– since I always assumed that the most natural method would be to use the support hand to hold the back of the receiver against the forearm like a blade type AR “pistol brace”; you probably wouldn’t want to do it for more than one magazine unless you were wearing a good jacket, but that’s not really what it was designed for.

    • Paul Zimmerli

      Bracing the back of the receiver against the forearm was Dale Davis’s original intent when he first designed this at Eglin AFB. I know this because I talked to him and handled the prototypes. It was also originally chambered in a .17 caliber round similar to the .17 Javelina. He designed this as an aircrew survival weapon. It wasn’t designed to be a sporting weapon — rather, it was to replace or augment the short-barreled .38 revolvers aircrew members carried.

    • iksnilol

      Why pistol brace in quotes, there’s people actually using them legitimately. Not everyone uses it as a SBR workaround.

  • Darren Hruska

    On a related note about the Colt IMP, here’s this experimental cartridge again.


  • iksnilol

    I hope he becomes a doctor, so we can call him Dr Strange.

    That’d be soooo worth it.

    • Dougscamo

      Cool character….think we’ve had Dr Strange discussions in the past…or is it?….

      • iksnilol

        I am not quite sure to be honest.

  • mechamaster

    I would like to see it in .22TCM or 9mm Conversion, or ( conceptualize ) 6,5 CBJ .
    Basically it can turned into bullpup PDW and more appropiate caliber in short barrel.

    • JustAHologram

      Or even 5.7x28mm

    • GD Ajax

      .22TCM is a fanboy round that is meant to stave of the obsolescence of a one hundred year old pistol.

    • roguetechie

      That would be the SS1 Sidewinder SMG…

      A gun even more rare and obscure than this. It’s only claim to fame is the Iranian embassy hostage rescue mission was supposed to use several of them as armament for some of the delta guys.

  • rs

    I used to own one of these. It was such a crappy gun that I sold it. Now that I’m a more serious collector, I regret that, but it really was a lousy gun.

    Mine couldn’t get through 10 rounds without a jam. The trigger guard kept falling off, and I couldn’t hit a pistol target at 25 yards with it. The rear sight is a sheet steel swivel on the back, and has to be hand turned to match the angle you’ve turned the front to … non-functional.

  • Garmanarnar

    This guy is such a dingus

  • roguetechie


    FWIW the reason why Hank’s firing of the gun looks just wrong and dangerous is because the way he’s choosing to do it IS actually wrong and dangerous…

    That’s not even closntended to be operated.

    As much as the arm gun has some pretty meh aspects to it, any gun will look absolutely stupid and dangerous if the person firing it is doing so in a way that’s stupid and dangerous.

    This said, Mack Gwinn didn’t do his design any favors when he deleted the pressure based pivot lock feature.

    For future reference to anyone who may get a chance to fire a bushmaster arm gun or an ss-1 sidewinder the proper and intended way of operating these guns are below.

    One handed use: if you want to fire one handed and accurately get a laser because you can’t do it right and use the sights! This is a hip shooting affair only!
    With your arm bent in a v and pistol grip at about belly button height clenching the butt of the gun with your bicep is proper firing stance.

    • Steve_7

      These were designed back in the days when people generally shot handguns one-handed. How I was shown to shoot it was using the support hand to hold the butt to your forearm, it was still hard to shoot though.

      • roguetechie

        Yeah, there’s a “proper” way to shoot both one and two handed which can be used to fire them safely and accurately once you get used to it.

  • Dave514

    I remember seeing a sub-gun whose magazine and action would rotate 360. I think the guy was from Texas. This was back in the early seventies I think. It was in 9mm.

    • roguetechie

      The ss1 sidewinder smg

  • NICEGUY777

    Sorry dudes but junk to me!!!!!!