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Semi-automatic copper airsoft gun (updated)

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Semi-automatic copper airsoft gun (updated)

Unread postAuthor: GalFisk » Sun Oct 30, 2005 8:29 am

I updated this post, since the original image links were long dead. The gun was also improved since the last post, and is firing pretty reliably. the only problem is that the trigger valve does not reset reliably with the current spring and 300 psi pressure (the design pressure), I may try some lithium grease and see if that loosens it.

Here is how the loading mechanism works. It is connected to the piston valve with a threaded rod,, when the valve opens, the piston moves left and takes the bolt with it.

the advantage to this mechanism is reliability and mechanical simplicity - there is only one moving part. It's also always synchronized to the firing of the cannon. I have adjusted the mechanism so it will only admit a BB into the chamber when the gun is pressurized - the piston face compresses somewhat under pressure and moves the bolt just far enough to open the breech.

A potential disadvantage to this mechanism is the force with which the bolt is actuated - I've had it make marks in the plastic BBs when they got caught at the edge of the bolt, and my first bolt snapped when an alu BB got caught.
This mechanism can be used for other round ammo as well, IIRC someone built a marble gun using it a couple of years ago. I made this gun as a prof of concept for this loading mechanism.

Edit: Here's the other cannon using this mechanism: http://www.spudfiles.com/forums/viewtopic,p,113007.html

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valveconcept.gif
This is a model of the internals of the valve, the piston can be seen to the very left.
valveconcept.gif (25.14 KiB) Viewed 1285 times
v3overview_small.jpg
I changed around the mounting of the trigger valve so how it's more comfortable for left-handed firing. I also put a piece of copper pipe inside the magazine, to prevent the airsoft BBs from jamming.
v2overview.jpg
The semi airsoft gun, (almost) finished. It has a calculated chamber volume of 70 cc, and a barrel length of 90 cm. the barrel id is 6.4mm, so the fit isn't perfect, but it's good enough.
Last edited by GalFisk on Mon Aug 24, 2009 4:05 am, edited 3 times in total.

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Unread postAuthor: Ballad_Black » Sun Oct 30, 2005 12:40 pm

Wow dude, nice gun and fragile looking design. I'd be scared I'd break it if I held it. Also, I think you put the gun in the wrong place, but I have a hang over and coulda mis-read.
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Unread postAuthor: Copperboy » Sun Jan 01, 2006 3:12 am

That's really a beauty! :D Although I don't quite get how the loading mechanism is linked the the pilot valve.
Do you live in Skandinavia? And if you do, from where do you order your parts?
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Unread postAuthor: drac » Fri Jan 20, 2006 7:25 am

I think Galfisk lives in Sweden.
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Unread postAuthor: GalFisk » Fri Jan 20, 2006 12:05 pm

thanks for the comments :)
I order my parts from Rinkaby Rör (http://www.rinkabyror.se) and Sigro (http://www.sigro.se), between them they have a really good selection.
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Unread postAuthor: djt » Wed May 17, 2006 6:27 pm

i like it alot. i have been wanting to build something similar but portable and small and either hand pumped to build up pressure or air compressor filled. hah i think i might be asking a bit too much. but all in all its a really nice gun.
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Unread postAuthor: Darkside 6ix » Wed May 17, 2006 6:35 pm

what type of valve is it?
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