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Would this blowback bolt design work?

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Would this blowback bolt design work?

Unread postAuthor: budabob07 » Wed May 23, 2012 2:59 pm

I'm wondering if the air pressure from this design would be sufficient to cycle the bolt. The pressure would be regulated at 100PSI. The valve is a 1/4" QEV piloted by a 3-way valve. The projectile is a standard 6mm airsoft BB and the barrel will be a 6.04mm tightbore ~25" barrel. Here is the bolt design.
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Unread postAuthor: jackssmirkingrevenge » Wed May 23, 2012 3:06 pm

With a blast of air from a QEV and the provision of a sufficiently tight o-ring detent as you drew it should work. The theory is easy, actually putting it together needs some thought :)
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Unread postAuthor: budabob07 » Wed May 23, 2012 3:13 pm

Would the bolt moving back cause a performance decrease? Or does it just depend on how tight you make the spring
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Unread postAuthor: jackssmirkingrevenge » Wed May 23, 2012 3:20 pm

ideally the projectile would have left the muzzle before the bolt reaches the magazine port. The fact that the bolt is heavier and its motion is opposed by the spring force means that it accelerates more slowly, being able to tune spring strength is an asset.
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Unread postAuthor: budabob07 » Wed May 23, 2012 3:21 pm

Alright thanks.
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Unread postAuthor: cammyd32 » Wed May 23, 2012 4:40 pm

I designed a device similar quite a while back, except my design used a valve opened by the BB itself, which meant the design wasn't continuous flow, (Here's a link if your interested: http://www.youtube.com/watch?v=ty3vONLgyyI ) never attempted making the design myself as it never seemed a challenging enough design. Can't see a reason your design wouldn't work though, just as long as you adjust the spring so it isn't too strong (perhaps have a threaded spring stop so you could adjust it perhaps?) and just make sure the detent isn't too loose or too tight, would be an interesting design if you got it working. Best of luck :)
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Unread postAuthor: Lazyboy » Wed May 23, 2012 6:15 pm

It should work, taking in to account the above posts.

If you are planning this to use as airsoft gun you will probably find it will use to much air, as in this gun of mine http://www.spudfiles.com/forums/viewtop ... tml#320537.

I am trying to reduce its air use, I will be very interested in how this works out.
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Unread postAuthor: budabob07 » Wed May 23, 2012 6:42 pm

For the air use, I plan on using a 1 cubic inch chamber at 100 (regulated) psi (GGDT says that'll give around 500fps with my setup). Assuming the air source is a standard 3000psi 48 cubic inch tank, that is 144000 cubic inch*psi. The airgun should use 100 cubic inch*psi, therefore theoretically giving around 1400 shots. However, I really doubt this is correct reasoning as I am completely guessing so can someone please correct me on this in the likely event I am wrong
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