.32 Cal Caselman Air-Powered Machine Gun (UPDATE: More photos)

The Caselman Air-Powered Machine Gun is an air gun designed to shoot .30 caliber slugs on full auto with approximately the same muzzle energy as a .32 ACP pistol. It was designed by Jeff Caselman in the 1980s as a way for any person to legally own a machine gun, one with enough power for self-defense. In 1990 Jeff sold the plans for the air machine gun for $19.99 and a instructional video on manufacturing it for $59.95. How long he sold these plans for, I don’t know. According to the late Mr. P A Luty, a master improvised gun maker himself, Jeff was never heard from again (although a video was published in 2011 showing a man named Jeff Caselman shooting a prototype air-powered shotgun). Luty took it upon himself to distribute the plans on his website. He called it “revolutionary in concept and design”.

Two weeks ago a reader, Mike, emailed us photos of a Caselman Air-Powered Machine Gun he built. It is a thing of beauty.


Mike has been running his at about 850 psi of air pressure, which results in 35 ft lbs of muzzle energy. The original plans specify it should be run at 3000 psi to give 125 ft lbs of muzzle energy.



Check out Mike’s blog. He make everything from violins to guns to homemade forges.

UPDATE: Mike sent in more photos …













13 14

IMG_3174 (Medium)

IMG_3175 (Medium)

IMG_3176 (Medium)

IMG_3183 (Medium)

IMG_3186 (Medium) IMG_3192 (Medium)

IMG_3193 (Medium)

IMG_3194 (Medium)

IMG_3195 (Medium)

IMG_3196 (Medium)

IMG_3197 (Medium)

IMG_3200 (Medium)

IMG_3201 (Medium)

IMG_3202 (Medium)

IMG_3206 (Medium)

IMG_3207 (Medium)

IMG_3208 (Medium)

IMG_3212 (Medium)

IMG_3214 (Medium)

IMG_3216 (Medium)

IMG_3217 (Medium)

IMG_3219 (Medium)

IMG_3220 (Medium)

IMG_3221 (Medium)

IMG_3227 (Medium)

IMG_3231 (Medium)

IMG_3232 (Medium)

IMG_3236 (Medium)

IMG_3254 (Medium)

IMG_3255 (Medium)

IMG_3256 (Medium)

IMG_3257 (Medium)

IMG_3258 (Medium)

IMG_3259 (Medium)

IMG_3263 (Medium)

IMG_3267 (Medium)

IMG_3271 (Medium)

IMG_3273 (Medium)

IMG_3286 (Medium)

IMG_3288 (Medium)

IMG_3290 (Medium)

IMG_3291 (Medium)

IMG_3292 (Medium)

IMG_3297 (Medium)

IMG_3298 (Medium)

IMG_3299 (Medium)

IMG_3304 (Medium)

IMG_3306 (Medium)

IMG_3307 (Medium)

IMG_3315 (Medium)

IMG_3316 (Medium)

IMG_3317 (Medium)

IMG_3318 (Medium)

IMG_3319 (Medium)

IMG_3321 (Medium)

IMG_3322 (Medium)

IMG_3323 (Medium)

IMG_3324 (Medium)

IMG_3330 (Medium)

IMG_3331 (Medium)

IMG_3332 (Medium)

IMG_3348 (Medium)

IMG_3354 (Medium)

IMG_3361 (Medium)

IMG_3364 (Medium)

IMG_3365 (Medium)

IMG_3366 (Medium)

IMG_3367 (Medium)

IMG_3370 (Medium)

IMG_3382 (Medium)

IMG_3383 (Medium)

IMG_3384 (Medium)

IMG_3386 (Medium)

IMG_3387 (Medium)

IMG_3388 (Medium)

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.


  • Graham 1

    I wonder how many shots the tank is good for before it needs to be replaced/ refilled

    • Mystick

      Larger tanks are available…

      • Eric S

        I always wanted to rig up a SCBA to an air rifle. Even the imminent explosive would be glorious.

        • Mystick

          As long as it’s regulated to what the seals in the gun will handle, it’s not a problem… adding an expansion chamber(which is remarkably similar to a suppressor in operation – if not function) to the air inlet will help even more with the seals not freezing up. Kind of like those full-auto BB guns at the carnival. They are pretty much hooked to a compressor’s tank, and are usually drop-fed(no cycling) into a live airstream. The magazine is sealed to the chamber pressure.

          I’ve seen one instance of modifying a multi-pump air rifle to accept a constant air source… but it still had to be “cycled” just like any other. You just didn’t have to pump it up. But it wasn’t at 800psi, I don’t believe. It was ugly, but it worked. Basically replacing the gun’s pump mechanism with bottle.

          There’s a formula floating around somewhere for bore diameter/projectile mass/PSI/muzzle velocity(probably temperature, too). I’m sure it could be calculated what the minimum pressure would be to move a projectile down the bore at any given velocity…

    • Mike Crumling

      it gets around 300 per 24 ounce co2 tank.

  • clinton notestine

    whens the ar-air upper coming out

    • Steve Truffer

      Been out for some time.

    • Rusty Shackleford

      Do you mean the thing that is a low powered .177 bb gun that is considered a firearm?

  • iksnilol

    The pressure can be regulated/changed? I think I heard that that on another website. Low pressure for plinking/fun, high pressure for social situations.

    PS: Good work, that is a unique gun!

    • DiverEngrSL17K

      Good question, Iksnilol. It wouldn’t be too difficult to add a simple pressure-adjustment system using a commercially-available pressure regulator and / or a needle valve. Some thought would be needed in configuring the set-up to keep it compact, streamlined and reasonably user-friendly, but it should be feasible.

  • DiverEngrSL17K

    Congratulations, Mike — Nice job with the machining and metal work ; I think the woodworking for the gun’s furniture is also very well done.

  • Bert

    Very interesting! I’ve been a paintball hobbyist for years, and I like this offset poppit-valve setup. It looks like a good way to reduce the OAL and complexity of the design without slamming the bolt into the rear of the receiver, at least as opposed to an inline valve.

    • DiverEngrSL17K

      Did you mean to say “poppet valve”?

  • 1911a145acp

    Well done sir!

  • Wetcoaster

    What’s the FPS for this thing? Gotta watch out for your local laws; http://en.wikipedia.org/wiki/Air_gun_laws

    In Canada, airguns with a muzzle velocity over 500 FPS are treated as firearms, and automatic firearms don’t fly so well with the RCMP.

    • DiverEngrSL17K

      Good point.

    • Porty1119

      I ran the math, assuming something like a .30 Carbine round massing 7 grams, and came out with a theoretical muzzle velocity of 750fps. So I suppose it is legally a firearm in Canada; however, given that you have a velocity limit rather than a KE limit (unlike some countries), you could shift to a heavier round for reduced velocity, or just lower the operating pressure. Given that a round change would require a lot of on-the-fly modifications to chamber size and the like, I’d just regulate the pressure. Considering your laws, I’d make it a hard limit (non-adjustable) so the weapon couldn’t be ‘converted’ to a ‘firearm’.

      Sorry if I’m talking out of my ass on the pressure issue. I’m an engineering student, not an airgun expert.

    • Sulaco

      That type of law restrictions are catching on in some states as well, NY and NJ and CA I think. If memory serves in NY city it is illegal to own an air gun of any kind…figures in a slave state…

      • valorius

        It is illegal to own a BB or airgun in Philadelphia too, but everyone just ignores the law.

        • Dr. Daniel Jackson

          As they should also do with any firearms laws,

    • elconquistidor

      Another reason why Canada sucks. You can buy commercially available air guns that shoot 1300 fps.

      • Wetcoaster

        You can find those up here just fine, but they fall under the same regulations as say, a .22 while < 500 FPS air guns don't need a firearms license to own.

        Where it really comes into play though, is with pistols since handguns are still registered and subject to a requirement for transport permits. It's a big step up in hassle compared to the difference between a low and a high velocity air rifle

  • John Daniels

    It’s a very cool project, however I feel it should be pointed out that anything that only generates 135 ft/lbs of energy is not suitable for self-defense. That energy level puts it somewhere between .22lr and .22WMR.

    • zardinuk

      It generates more ft/lb per second than you’re gonna be doing with your glock… I’d take this over a baseball bat.

    • nova3930

      At a high enough rate of fire, even .22 short becomes as deadly as a .50BMG. Just imagine a .22 short Dillon minigun lol

    • valorius

      I disagree. More people get killed by 22 LR than any other caliber.

  • 101nomad

    never know when this site is working

  • 101nomad

    When will it be available to the military?

    • Steve (TFB Editor)

      Air guns were originally military weapons.

      • Sulaco

        And were used for hunting in the 1800’s, Lewis and Clark had one along that would not look out of place in todays scene…

      • 101nomad

        Yes they were. Austria, was it? My memory is fading. They used them for something like 30 years? I went to school when there was such a thing as an education. We even studied Lewis and Clark. I was in the military in the 60s, you know, the dark ages. So I may be a bit rusty on the real world of today.

  • Flipity Flopity

    Wearing flip flops in a metalworking shop tells me all I need to know about this guy.

    Impressive work though.

    • elconquistidor

      For taking pictures? Yeah I think it’s OK.

      • bob

        I wore flip-flops in my shop all the time. I also fry up bacon…with my shirt off.

        Some mutherf#ckers are just more confident than others.

        • elconquistidor


  • gunslinger

    does it meet the 12″ FBI penetration requirement?

    • Nathan Redbeard

      Hmmm…well it’s about 140 gauge, so we have a lead ball weighing 50 grains generating about 130 ft/lbs of energy, which comes out to 1082 fps… lol, I have no idea, never shot ballistic gelatin, but there’s the numbers, someone else who has experience figure that one out.

  • Rudi


    • Kris

      The question is how much are you willing to pay for it?

  • Doom

    wow that looks quite complicated, could you not do the same thing with a quality Paintball gun and use lead or glass pellets at full gas power? would that function like a gun or would the projectiles be too heavy and slow?

    I think I would rather have a luty pipe gun… though this would be nice and quiet. 125 ft pounds sounds like a toy, isnt 9mm in a handgun like 5-600 ft-lbs? if not more?

    • Mike C

      I wouldn’t feel safe putting anything more than 1200psi through a paintball gun as most are aluminum. This gun is steel, and the plans say it was designed to hold 3000 psi, big difference. Supposedly a .45 cal version was built by the original designer that produced around 300 ft lb.

      • dan

        You realize you can buy non carbon wrapped aluminum airtanks right? C02 comes in at 1800psi and you can get nitrogen/compressed air tanks capable of 3000psi that are not carbon wrapped so again why not aluminum?

        • Mike C.

          Those non carbon wrapped aluminum air tanks have a working pressure of 1800 psi. The co2 in those tanks is at 969 psi at 80 degrees. They were designed to withstand those types of pressure. Paintball guns work off of around 1000psi and many were regulated down from there. Hpa tanks, when used on paintball guns, are regulated down to a lower pressure. The guns were never designed to handle 3000 psi. You could convert a paintball gun, but it’s not going to be able to put out 125ft lbs. if all you wanted was 35 ft lbs then yes, totally possible.

  • Mehul Kamdar

    I’d like to see an independent chronograph test. I am NOT convinced by the MV / ME figures from that tiny air bottle.

  • Adam

    Now find 3 cnc shops and start cranking them out…. you would have people lining up around the corner….

  • Brian C

    Very nice work ! I will have to show this blog to Mr Caselman next time I’m out his direction.

    • Mike C.

      I would love to hear his opinion of my work. Please do post what he says about it.

  • Jerod J Husvar

    Did I miss a link to improved blueprints? The last I heard there were a few flaws in the plans originally sold? Show us the love, I have machinists friends.