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Variable speed BBMG breech

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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Variable speed BBMG breech

Unread postAuthor: evilvet » Sat Feb 12, 2011 4:05 am

http://www.youtube.com/watch?v=cguBDipNpQE

This came from one of Jack's postings, an idea for a cam operated bolt.
The original used a hollow bolt to open and close the air feed, I am trying something slightly different.

Once funny outcome is that when it is hooked up to 100psi with 50 litres of storage you get this great steam train "choof choof" effect as the bolt opens and closes.

Comments / ideas ?

Ta
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Unread postAuthor: jrrdw » Sat Feb 12, 2011 6:19 am

Show us what your working on. Can't really comment on something that we don't know what exactly it is...
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Unread postAuthor: Crna Legija » Sat Feb 12, 2011 8:47 am

looks like a wierd sex toy :lol:

love the clear plastic because you can see the mechanism, iv seen jsr drawings but idk if he ever built one
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 12, 2011 9:45 am

[youtube]http://www.youtube.com/watch?v=cguBDipNpQE[/youtube]

looks like a wierd sex toy


I have to admit that having seen similar mechanisms used in a questionable context, that was my first thought.

*ahem*

Looking great so far though, I assume you're planning a more compact portable setup eventually? What you tried it with a barrel and projectiles to gauge power?
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Unread postAuthor: POLAND_SPUD » Sat Feb 12, 2011 9:46 am

looks like a wierd sex toy
Aren't you to young to watch stuff like that ? :lol:
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Unread postAuthor: Crna Legija » Sat Feb 12, 2011 11:36 am

just turned 18, don't need to lie to that web site anymore
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Unread postAuthor: evilvet » Sat Feb 12, 2011 2:37 pm

-_- wrote:looks like a wierd sex toy :lol:

love the clear plastic because you can see the mechanism, iv seen jsr drawings but idk if he ever built one


Yeah, the acrylic blocks are great, though they can be daunting to machine as the tend to split & crack. It does make it easy to see exactly what is going on though.
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Unread postAuthor: evilvet » Sat Feb 12, 2011 2:53 pm

looks like a wierd sex toy



I have to admit that having seen similar mechanisms used in a questionable context, that was my first thought.

*ahem*


You all watch too much naughty video

Looking great so far though, I assume you're planning a more compact portable setup eventually? What you tried it with a barrel and projectiles to gauge power?


As to power, with my shop compressor running at 100psi and a tube feed of 20 rounds, all 20 went through the 3ply of my workshop door. I used a 5.0mm barrel 600mm long and the rounds are standard .177BB :D Note to forum, always check alignment of the barrel before doing test firing.

I probably won't shrink it down too much as the final housing will look something like this :)


Image :)
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Last edited by evilvet on Sat Feb 12, 2011 3:14 pm, edited 1 time in total.
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Unread postAuthor: jackssmirkingrevenge » Sat Feb 12, 2011 3:10 pm

evilvet wrote:You all watch too much -------


I would edit that in order to avoid giving youngsters specific ideas, besides there are far better sites around :D

As to power, with my shop compressor running at 100psi and a tube feed of 20 rounds, all 20 went through the 3ply of my workshop door. I used a 5.0mm barrel 600mm long and the rounds are standard .177BB :D Note to forum, always check alignment of the barrel before doing test firing.


haha, NOW you are a fully fledged member of spudfiles!
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Unread postAuthor: saefroch » Sat Feb 12, 2011 3:38 pm

evilvet wrote:As to power, with my shop compressor running at 100psi and a tube feed of 20 rounds, all 20 went through the 3ply of my workshop door. I used a 5.0mm barrel 600mm long and the rounds are standard .177BB Note to forum, always check alignment of the barrel before doing test firing.
Not too shabby. Yesterday I made an incredible solid-steel sectional density-stabilized projectile. Possibly too incredible. It passed cleanly through my backstop, the neighbor's fence, his other fence, and the fence of the people two doors down.
What's more, because the sound from a pneumatic dissipates over distance so much, none of them have any idea.

Just because you know where the projectile's headed doesn't mean you know how far it's headed.

I really like the breech idea (and know exactly the url of the site mentioned :roll:), have you considered building a compressor using that?
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Unread postAuthor: evilvet » Sat Feb 12, 2011 9:20 pm

have you considered building a compressor using that?

Could you elaborate on that please ?
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Unread postAuthor: Crna Legija » Sat Feb 12, 2011 10:47 pm

do you have a seal on the moving bolt?
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Unread postAuthor: evilvet » Sat Feb 12, 2011 11:19 pm

-_- wrote:do you have a seal on the moving bolt?

No I don't and I know it is one of the issues I could address.

That said, the output is pretty effective as is: the bolt is 4.5mm in a 5.0mm hole with a good heavy layer of gun oil in the action. Obviously there is some blow back past the bolt but perhaps not enough to warrant me trying to fit an O ring.
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Unread postAuthor: jackssmirkingrevenge » Sun Feb 13, 2011 12:04 am

evilvet wrote:the bolt is 4.5mm in a 5.0mm hole with a good heavy layer of gun oil in the action. Obviously there is some blow back past the bolt but perhaps not enough to warrant me trying to fit an O ring.


Think again ;)
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Unread postAuthor: evilvet » Sun Feb 13, 2011 12:31 am

Jack is a nitpicker, nah nah nah :P

33% increase in muzzle energy for like projectiles against barrel I/D is one thing, but in this case I am talking about the potential energy loss past a viscous liquid seal versus the main air stream down the barrel.

When the bolt is in the retracted position behind the air inlet (about 90% of the duty cycle) the path of least resistance is forward.

So there, nyah nyah.

I suppose I could make an O ring from some epoxy though...............
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