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HPA airsoft BBMG w/detent seal

Built a BB Machine Gun? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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HPA airsoft BBMG w/detent seal

Unread postAuthor: jackssmirkingrevenge » Tue Jul 27, 2010 3:15 pm

This was originally intended to be a single shot high velocity gun, but thanks to POLAND_SPUD for the thought :P ;) pour some BBs into the chamber et voila, full auto!

Nothing much to look at, basically the setup is as follows:

paintball tank->ASA adapter->BB chamber->detent seal->barrel

The barrel is 36 inches long and I'm running it at 800 psi, look at it go:

[youtube]http://youtube.com/watch?v=otpqK8GybcQ[/youtube]

and slowed down to 420 frames per second, apologies for the poor lighting:

[youtube]http://youtube.com/watch?v=Ct69Eg0BmwY[/youtube]

Very reliable, fires every time unlike some other attempts, I suspect this is more to do than the low weight:volume ratio of the projectiles than anything else. Also if you look at the targets, some dents on the biscuit tin suggest some rounds had less power than others, which is an indication of either double feeding or one round blocking the breech before the preceeding round has left the barrel.
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the firing setup, crooked but pretty is as pretty does ;)
CIMG0338.JPG
biscuit tin and 1/4" fibre board targets
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Unread postAuthor: jakethebeast » Tue Jul 27, 2010 3:26 pm

simple is often beatifull, this time it is :)
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Unread postAuthor: POLAND_SPUD » Tue Jul 27, 2010 3:45 pm

double feeding or one round blocking the breech before the preceding round has left the barrel
you already know how to fix that (hint)

could you add a cutaway view of the launcher ??
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 27, 2010 4:08 pm

POLAND_SPUD wrote:you already know how to fix that (hint)


Certianly one option I'll be thinking about, waiting for my pipe-bending springs to arrive...

could you add a cutaway view of the launcher?


Here you go, nothing spectacular:
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Unread postAuthor: POLAND_SPUD » Tue Jul 27, 2010 4:23 pm

oh damn it's almost as simple as mine...
ohh you don't need that bolt&nut... just build a compression fitting

ohh and finally... it seems that you don't need epoxy at all... you can build the second prototype completely from standard fittings
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Unread postAuthor: jackssmirkingrevenge » Tue Jul 27, 2010 10:39 pm

POLAND_SPUD wrote:oh you don't need that bolt & nut... just build a compression fitting


In this case, it was intended as a single shot launcher, but I see your point.

it seems that you don't need epoxy at all... you can build the second prototype completely from standard fittings


Well, technically... but life without binary adhesive? *shudder*

I don't think I'll stick with airsoft though. While this thing is extremely fun to shoot, I haven't managed to find a single intact BB (though there are fragments friggin everywhere) and I think I'd want something a bit more efficient in terms of sectional density...
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Unread postAuthor: POLAND_SPUD » Wed Jul 28, 2010 1:18 am

6mm steel ball bearings (0.88g) sounds heavy enough ?? well you might as well switch to lead 6mm BBs or 5.5 round pellets
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 28, 2010 1:23 am

I would prefer 4.5mm, granted less powerful but much easier and cheaper to obtain.
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Unread postAuthor: POLAND_SPUD » Wed Jul 28, 2010 2:00 am

ohh come on you can't get 5.5mm cal pellets ??
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 28, 2010 2:55 am

Never found the round ones available in Epoxyland, and there aren't that many gun shops to choose from :roll:
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Unread postAuthor: SpudFarm » Wed Jul 28, 2010 3:26 am

Nice! I like those easy to build guns.
Since I have very limited knowlege with small caliber full auto launchers I'll just ask something else I have been wondering about;

How often do you buy epoxy?
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 28, 2010 3:34 am

SpudFarm wrote:How often do you buy epoxy?


Not as often as you might think, I use very little per project, and always try to mix only as much as I will need to avoid waste. I bought 1.2Kg last year and there's still half of it left.
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Unread postAuthor: SpudFarm » Wed Jul 28, 2010 3:37 am

jackssmirkingrevenge wrote:I bought 1.2Kg last year


Well... That is certainly above average :P

But lets not continue on this, your thread will probably be hijacked and everyone talks about your epoxy instead of your BBMG.
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Unread postAuthor: jackssmirkingrevenge » Wed Jul 28, 2010 11:14 am

Back on topic then, here it is in action against a plastic pen holder - not that spectacular, but it illustrates the "jackhammer" principle I often mention which gives BBMGs their power at close range - concentrated impacts over a small area in quick succession, particularly at 0:24 on the bottom left corner:

[youtube]http://www.youtube.com/watch?v=bewNtgfLDuc[/youtube]
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Unread postAuthor: POLAND_SPUD » Thu Jul 29, 2010 1:49 pm

oh come on... post something new
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