This article details the construction methods of a home built air machine gun. Included are detailed construction diagrams and methodology. This article is based upon a freely distributed file known as “The Caselman Air Machine Gun“. Here the file is represented in HTML form and has been revised by myself for spelling and grammar errors. Some sections relating to purchasing pre-built components have been removed as the original author (Jeff Caselman) is no longer contactable.
The Shop Built
DELIVERS 32 ACP POWER
DESIGN - HAND HELD SELECTIVE FIRE AUTOMATIC
SYSTEM OF OPERATION - BLOW BACK
CALIBER-30 (.311 BOTTOM GROOVE)
BARREL LENGTH - 20″ to 24″
MAGAZINE CAPACITY - 30 BULLETS (85 to 100 gr.)
OVERALL LENGTH - APPROX. 45″
WEIGHT - 10 to 12 LBS.
BY CASELMAN EXPLORATIONS
The article is broken into several sections.
- How the Gun Works
- Construction Tips
- Pressure & Performance
- Trouble Shooting
- Parts List
- Construction Diagrams & Manufactured examples
You may wish to browse the images on Page 4 to make sense of the Construction Tips.
I started working on the concept of a high powered pneumatic rifle in 1979. (Although the idea started cooking as a young boy). I started with a small lathe and just a few tools, located on a back porch shop. I’ve made a lot of progress, with added tooling, and a better place to work, but it has been slow going, as I had to make a living to support my family, build up my tools, and be creative with virtually no money to spend on the project. The break-through is finally here, and after several prototypes, I have something to share and hopefully in time to beat gun prohibition and share these plans with you.
With the gun prohibition staring us in the face, it’s nice to know you don’t have to be without protection. This gun was designed with the idea that any and all guns could be banned. Ammo could also become illegal or unavailable. That’s why we strongly urge you to save these plans. Having the security of knowing you can make a high-powered automatic with high pressure air, and mold your own bullets.
This weapon was developed as a self-sufficient, pneumatic alternative for home protection & defense, and also inexpensive machine gun shooting and enjoyment. It can be extremely powerful for 30 shots, or tuned down to 150 shots for shooting pleasure.
This alternative weapon can be built on a lathe with a milling
attachment with basic shop tools.
If extreme pressure is to be used with this gun, specific steels professional workmanship and tank selection are of the utmost importance.
Improper handling or construction of this weapon can be dangerous. Caution should always be applied as with any powerful gun. Keep in mind a modern high pressure gun such as a 30-06 develops 50,000 lbs. of pressure on firing, if improperly handled is extremely dangerous also.
How the Gun Works
This gun is a basic blow back system designed to operate from the peak pressure of a pre-pumped detachable tank of approx. 100 cubic in. capacity which is the shoulder stock. The gun has a 30 round detachable magazine which releases all its bullets to flow freely into the loading port when snapped into the magazine housing. The bullet mold was selected to cast a 1 in 40 parts tin bullet, which would strip off each other without hanging up.
Pressure drops slightly from shot to shot, but the valve tends to
compensate for it somewhat, as it is harder to strike open at higher
pressure and lets more air out at lower pressure. A good polish of
receiver tube ID., bolt & striker are very important because it
takes over a 150 lb. blow to open the firing valve, which has to recock
on momentum of the bolt.
Manual cocking is done by forcing the cocking pin on the striker into the bolt so it will come back with the striker. Upon letting go, the sear holds the striker, the cocking pin spring releases the bolt, letting it pick a bullet out of the loading port shoving it into the firing chamber past the air inlet from the firing valve. The bolt being in the proper place for firing allows the disconnector to come forward by going into the small off-set slot in the bottom of the bolt body. This lets the disconnector pull down the sear upon pulling the trigger, letting the striker hit the firing valve. In the first stage of the trigger, the striker follower will recoil with the bolt and hit the disconnector releasing the sear, which establishes semi-auto fire, as you pull on down to the next stage the auto sear trip comes up to trip the sear for the next shot when the bolt comes home.
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