I started on my mission to build my first pneumatic only knowing that I wanted to a) build a golfball gun, b) a coaxial model and c) somehow utilize one of those dumb 2' pieces of 3" PVC that Home Depot and Lowes love to sell these days. After considerable time and effort, I came up with "Bofors Little Brother", named after the Swedish 40mm anti-aircraft guns used on allied ships in WWII because they have similar look and share a similar caliber.
Features include:
- 48" 1.5" SDR 21 barrel
- c:b = 1:1
- overall gun length about 5'
- 3" barrel sealing piston, multiple plastic paint coatings to build out to ideal diameter
- 3/8" to 1/2" piston travel
- 3/4" Orbit Watermaster pilot valve, 3/4" brass and sched 80 piped, blowgun actuated
- schrader air fill
- screw ball stop and barrel dimple, holds ball in place reliably
- cool 2 tone flat black/glossy black paint job
- cool looking but useless barrel noozle
- deep throated, fast pulse shots, 50 - 100 psi feels about right in this gun. Laser beam GB shots...
After this project, I guess I still count myself a combustion man at heart. The whole air compressor requirement for medium and big guns makes me really enjoy the advanced combustion's always ready-to-go anywhere appeal. However, I wanted some pneumatic experience and this has been invaluable. The toughest part was getting the piston right and figuring out what order and what type adhesives to use when finally gluing the coax body and barrel together. You need a set of octupus arms to do everything you need to do almost all at once. You don't get a do over with a socket weld. Epoxy is my new best friend...

Check out a plywood-shot video here:
[youtube]http://www.youtube.com/watch?v=xzfnXruYvxw
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And damage closeup:
[youtube]http://www.youtube.com/watch?v=tGnaGFtSeMs
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