The Caselman air machinegun was designed in the late 70s by Jeff Caselman. Several
were made and sold, along with plans and a construction video. The plans
are available for download at a number of locations on the web. Jeff built
several of the guns in 9mm caliber, one in .45 caliber, and one in .30 caliber.
The .30 caliber plans show .32 ACP power which is about 125 ft-lbs per shot.
The larger calibers may produce about 300 ft-lbs of energy per shot. The
original used a steel tank attached to the gun, with external plumbing directing
the air to the air chamber.
The staff of one at Airmachinegun.com has built a working Caselman using the
plans available on the internet. During the construction, several errors
were noted in the plans and will be covered here. In addition, changes
were made to convert it to shoot .32 caliber, 45 grain round lead balls.
With the valve sized as per the plans, the gun produces about 75 ft-lbs of
energy per shot and cycles over 1200 rpm. In testing, several bursts
cycled at 1500 rpm. Operation was not reliable and sustainable at 1500 rpm, so significant weight was added to the striker to slow the rate of fire
down to about 800 rpm. At that rate it cycles flawlessly and has a very
pleasing rat-a-tat-tat sound.
This section of the website will show the plan corrections, modifications,
new parts, pictures, and how to assemble and test the Caselman. The
information is broken down into the following sections:
- Parts List
The parts lists contains all of the parts and recommended
materials, as well as standard sizes and cost estimates for purchasing parts
from a small metal supplier.
The valve and air holding chamber construction is shown.
There is a section on the use of UHMW PE as a valve seat material, which has
The receiver tube is made from DOM steel tubing.
- Trigger & Magazine Housing
There are modifications shown here for making a removable magazine
housing so drum or other magazine types can be used.
There is a
detailed drawing and construction sequence for building the new round ball magazine.
- Bolt & Striker
The bolt and striker recoil after each shot and the weight of those
parts can be modified to change the rate of fire. Two methods are
shown. One is an add-on piece, the second is a new striker.
- Barrel & Caliber Changes
To make caliber changes easier and barrel selection and profile
changes much easier, the barrel is attached with a barrel holder which also
incorporates the new ammo port for the round ball magazines.
- Select-fire Trigger
The original used a full-auto sear trip to accomplish selectable
semi-auto and full-auto fire. The original is shown as well as several
options for full-auto only that can reduce the tuning time, but only allow
full-auto fire. For AirMachineGun.com, the full-auto only version was
done first to prove the functioning.
- Air Supply
A steel tank of about 100 cubic inches was used on the originals.
Here are options for installing a wood stock in place of the tank and using
a remote air tank and line for power.
Some tips that are helpful in the assembly of the subsystems are
- Testing & Performance
If you make it to this part, the end is in sight, and if you have
done accurate work, you are close to having a full-auto air machine gun that
produces 75 ft-lbs of energy for each shot. Test velocities for the
stock valve firing other calibers are listed.