Flup » Front Page Articles
· Community Forum
A critical mass of stupidity.


The Caselman air powered machine gun

(Local Cached Copy)

April 7th, 2007 by bobsled

Pressure & Performance

There are many sources of air. Dive shops, divers tanks, small DC compressors from military surplus, aircraft strut pumps and shop built hand and motor driven, two & three stage pumps. A good starting pressure is 3000 lbs., although I am sure the gun will operate as low as 1000 lbs. with some tuning. Keep in mind that liquid C02 is 1000 lbs. at 83 degrees, and as long as there is a liquid portion in the tank the pressure would remain the same at that temperature. This would give several hundred shots per tank and it could be filled from a fire extinguisher.

Our velocity formula is V = root(2AD). Take the cross section of the .311 bore (.0759) by the air pressure (3000) = 2277 X the # of 100 gr. bullets per lb. (70) = 15939 gives acceleration in g’s
X 32.2 = 513235.8 X twice the barrel length in feet (4) root(2052943.2) equals 1432.8 ideal velocity. Our goal is to operate 70% efficient which would give 1000 fps.

Trouble Shooting

1. Weapon Won’t Recock

  • Too much spring tension
  • Weak strike on valve
  • Striker or bolt assembly binding

2. Quits Firing After Weak Second Shot

  • Sear not catching striker
  • Spring tension wrong

3. Jamming

  • Check alignment of magazine to loading port
  • Spring to weak in magazine
  • Bad bullet design
  • Bullet too soft
  • Need radius from loading port to bore axis & polished

4. Semi-Auto Function Fails

  • Sear binding or lack of upward tension
  • Trigger spring to weak
  • Disconnector to sear relationship off

5. Excessive Loading Port Pressure

  • Sear binding or lack of upward tension
  • Bullets too hard
  • Valve stem to long

6. Low Power

  • Weak strike on valve
  • Valve stem too short
  • Binding in striker assembly
  • Barrel needs lapped
  • Bolt 0 ring blown

Next up, Parts list and Construction Diagrams.

Pages: 1 2 3 4

Discuss »


Copyright © 2007 www.flup.ws