The Curious History of the Bushmaster Bullpup Pistol has posted up a fascinating story into the history of what ultimately became the Bushmaster Pistol Bullpup. As part of their War is Boring series, they stumble upon and cover something that isn’t boring.



In 1969, engineers at Colt offered the U.S. Air Force a unique lightweight gun, primarily for bomber crews. Since the unusual-looking rifle had no butt stock, shooters would have had to brace the so-called Individual Multi-Purpose Weapon against their bicep.

“Consideration was … given to what an aircrewman might have with him when he bailed out or what he might find on the ground which could serve as a stock,” stated an official Air Force report. “The only practical solution was the man’s arm.”

I recommend you hit link to be be taken the article and catch up on one of the modest beginnings of an iconic, albiet niche, rifle and the company it spawned. 


Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • Here is the report generated by Colt for their USAF contract:

  • In some ways, it reminds me of the british L22A1, but a lot shorter and a lot more barebones.

  • axel

    Why not just add a compact, collapsible stock?

    • Kitsuneki

      Also why not .223 Rem, and why not build from ar-15 parts?

  • iksnilol

    This could be interesting if chambered in 300 BLK (since it doesn’t have problems with short barrels).

    What is the length and barrel length of the Bushmaster? Haven’t found much info about it online.

    • Actually, there was one IMP that was rechambered to .30 caliber for suppressed use. There were a couple of cartridge configurations tried, ranging from a chopped .30 Carbine case to chopped .221 Remington cases, one with a straight taper and the other bottle-necked.

    • Zachary marrs

      there are 5.56 rounds that don’t have trouble with velocity

      • iksnilol

        With 23 (9 inch) barrels?

        • Zachary marrs


          M855 and m193 are velocity dependent, but not rounds like mk262 and mk 318

          • iksnilol

            Yeah, you got a point there. But for every round of mk262 or mk318, how many rounds of m855 or m193 is there?

            I can get ammo for my AK that would work optimally in a 23 cm barrel, but yet I go for the 30 cm barrel because it has better results with common ammo.

          • Zachary marrs

            I can also find ammo (very easily at that) that can work well in sbr’s

            There are more than 4 types of 5.56 ammo

  • Phillip Cooper

    Very cool design!

  • John Yossarian

    Against the bicep? Maybe it’s because I’m only 5’7″, but my anatomy certainly has no problem compressing itself to where I can shoulder a firearm such as this.

    • Avery

      Airsoft versions of the Arm Pistol exist and that’s pretty much how they tend to be used, if not just “spray and pray”. I know airsoft doesn’t have the recoil of real 5.56mm, but it’s a feasible design. I really think that there’s a market for them today and an update, especially with a free-floating rail mount instead of the leaf sights, would be appreciated.

      • Cymond

        Airsooft also doesn’t spit hot brass into your face from the ejection port on the top (yes, seriously, the top) of the gun.

  • William Johnson

    Always regret not buying one of these in the 80s when I had a chance at a gun show. Also missed a cheap webley in .455

    • DaveP.

      I don’t miss my chance at an Arm Gun, but the High Standard M-10 and the transferable Mac-11 I let walk by (back when the price for the Mac was still three digits) occasionally make me kick myself, after all these years.

  • Chris

    There are several versions of this available for viewing at the Air Force armament museum at eglin AFB, including one in .222 cal. Yes, 222.

    • That was probably a reference to the experimental “.222 High-Velocity” load. See the following thread at the International Ammunition Association forum:

      There was also experimentation with a hybrid polymer body/metal base case with a sabotted .17 caliber projectile.

  • Zebra Dun

    Oh yes, The infamous Arm Gun.
    I would guess no one expected to shoot it enough to get hot.

  • TechnoTriticale

    I was living in Windham ME at the time these were being made in the (.223) Bushmaster form. I visited the factory to try one, and might even have bought one, but I could tell from holding it that the sights were entirely decorative (I didn’t test fire it, and didn’t need to). It was too expensive as a novelty, and far from assured to become a collectible.

  • Don Ward

    I like how we are all calling it a pistol today. But the original documents with the photo above and the Patent info that Daniel Watters linked show that the manufacturers consider it to be a rifle.

    • Gwinn certainly sold it as a Title 1 Pistol; to call it otherwise would risk reclassification as a Title 2 Short-Barreled Rifle. There was a series of court cases during the late 1970s involving Gwinn’s arrest for carrying the Bushmaster concealed, and while there was question whether it legally qualified as a “concealed pistol” under state law, Gwinn was still nailed as a felon in possession of a pistol.

      • Don Ward

        Yes. Yes. Because we live in a world where a 16-inch Colt “Buntline Special” with a detachable buttstock is a rifle but the exact same historic gun with a 12-inch barrel is a Title 2 Short-Barreled Rifle. And if you you detach the buttstock on either, they both become pistols again.

        That doesn’t change the fact that these were originally billed as rifles despite the non-sense with ATF classification.

        Interesting bit of trivia with the arrest info.

        • Wouldn’t they be plenty old enough to be exempt from the NFA?

  • Thomas

    Somebody ought to revive this design and put it into production. It would really sell in todays market.

  • Just sayin…

    Using your bicep as a stock? The ATF wouldn’t go for that.

    • andrey kireev

      By using your bicep as a stock, you re-design your arm into an SBR and have to file $200 tax stamp with proper paperwork.

  • dan citizen

    I tried one and liked it. Neat gun, it’d be fun to see a modern version.

  • Darren Hruska

    The Colt IMP is perhaps considered to be one of the earliest forerunners to the modern PDW concept. It was made not only for the .221 Fireball cartridge, but also for some proprietary 7.62x28mm cartridge. This cartridge apparently helped “inspire” the .300 AAC Blackout cartridge and the AAC Low-Visibility Carbine, the “Honey Badger.”