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What type of breech?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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What type of breech?

Unread postAuthor: Dave_424 » Sun Oct 04, 2009 11:50 am

Hey, im making a popoff QEV airsoft gun and need some opinions about what breech i should machine. I want it mechanical so no double feeds etc not juat a tee magazine.

The way the QEV is arranged, the barre port is sticking upwards so I was thinking a blowback breech but am having trouble designing one

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Unread postAuthor: jackssmirkingrevenge » Sun Oct 04, 2009 12:02 pm

Something like this?

Image

It will need a considerable blast of air to operate though, you might want a larger diameter piston to ensure reliable function.

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Unread postAuthor: POLAND_SPUD » Sun Oct 04, 2009 12:03 pm

you might use a directionally control valve + air cylinder combo as i used on my semi auto (lol I think I should have named it because now I have to refer to it as 'my semi auto') :wink:
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Unread postAuthor: jackssmirkingrevenge » Sun Oct 04, 2009 12:05 pm

If you want an independent breech I think the blow-forward is much mroe reliable and easier to achieve.

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Unread postAuthor: al-xg » Sun Oct 04, 2009 12:52 pm

Or similar to POLAND_SPUDs suggestion but without a 5/2 valve: an air cylinder connected to the chamber. Moves forward while chamber fills, retracts only once projectile has left and the pressure drops.
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Unread postAuthor: POLAND_SPUD » Sun Oct 04, 2009 1:23 pm

well yeah I would have used 3/2 valve but the only one I could use then was 5/2 valve (because both of 3 way valves that I have are 1/8" and I didn't have the right fittings then)

5/2 valve
hmm.. that's interesting... you're the first person here that refers to 5 way 2 position valves in this way... even though it's very convenient it seems it's only used in europe


@dave
you could either use off-the-shelf parts (easier and cheaper) or machine them yourself (more compact)
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