Semi-auto .402 cal work in progress

Show us your pneumatic spud gun! Discuss pneumatic (compressed gas) powered potato guns and related accessories. Valve types, actuation, pipe, materials, fittings, compressors, safety, gas choices, and more.
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JDP12
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Sun Feb 19, 2012 6:56 pm

Here's another gun I'm working on while I'm at college: Using a 3 way valve with a slide valve. Right now it isn't magazine loading... I need some ideas on how to make an easy mag load for this?

I plan on replacing the rubber piston inside the valve with a steel washer/rubber sealing face so this can run at unregged CO2.

Most I've tested this with is 140 psi and a loose fitting 3/8" caliber ball bearing. Even with a loose projectile and low pressure, results were extremely promising, so power outputs when its all done are promising.

Will run off 12 gram CO2 cartridges- you can see the adapter in the picture.

Things I'll be working on:

1) Some sort of magazine.. Any ideas would be welcome.
2) Make it CO2 compatible
3) Try and build some sort of body for this: this is another area I could use some help with- Would like a fairly easy way to build this body, right now I'm thinking of casting it somehow.. but it could be a pain in the arse.
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killerbanjo
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Sun Feb 19, 2012 7:08 pm

Looking good so far, you do know those co2 adaptors are regulated for bike tyres though right?

Get one of these :)

http://www.ebay.co.uk/itm/Quick-Change- ... 2522wt_902
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JDP12
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Sun Feb 19, 2012 7:18 pm

i dont think they are... its just got a straight trigger on it that allows CO2 to flow into it. it's very simple, i can't see how it'd be regulated.

I'm not saying your wrong.. it just doesn't seem likely?
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Gun Freak
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Sun Feb 19, 2012 7:22 pm

I don't think they're regulated.

DO NOT check out the loader on Mark F's automatic marble gun. It's a like a little paddle. If it works for full auto, it'll work for semi.

:D
Last edited by Gun Freak on Mon Feb 20, 2012 9:20 am, edited 1 time in total.
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killerbanjo
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Sun Feb 19, 2012 7:32 pm

Im pretty sure they are, otherwise you would get people blowing up their bike tyres :P Still i might be wrong though
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Gun Freak
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Sun Feb 19, 2012 8:00 pm

I'm pretty sure they're not, because tires use anywhere from 30 to 160 psi.
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JDP12
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Sun Feb 19, 2012 8:02 pm

I don't think they have to be regulated, since of the expansion of the gas inside the inner tube.
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clemsonguy1125
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Sun Feb 19, 2012 8:15 pm

What type of threads does the main valve have?
That is all.
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JDP12
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Sun Feb 19, 2012 9:10 pm

the main valve and slide valve have 1/4" BSPP threads. The main valve output has a 1/2" BSPP thread. As such I had to get some adapters from mcmaster.

As far as projectiles- it's 3/8" ball bearings, and I'll make some foil sabots for them so they actually fit. As far as a magazine, still not sure what I'll do. It'll probably be some sort of aluminum rectangular tubing since the sabots will be slightly longer than they are wide.

And as far as a body goes- figure I'd find a nerf gun cheap enough to just cut up and bondo the gun into, then paint it a different color other than all the absurd colors they decide to make nerf guns.

For now, I'm gonna work on makin the sabots and finding a nerf gun suitable to fit the body in. Actually modifying it to have a mag will come later as that'll require a bit more time.
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jackssmirkingrevenge
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Mon Feb 20, 2012 1:31 am

haha, I recognise some of those parts :) good luck with it!
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JDP12
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Mon Feb 20, 2012 8:49 am

Indeed, teh parts were ordered straight from where you recommended. and they work damn good. Any tips on makin the piston for 800 psi? Im thinkin i'm just gonna epoxy some rubber to a washer, but do I have to worry about the length of it, or where to place it?
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Mon Feb 20, 2012 9:01 am

Gun Freak wrote:Check out the loader on Mark F's automatic marble gun.
No! :D

If you read further in that thread, you'll see that it have me a lot of problems. It works decent enough on larger projectiles like golfballs, but doesn't have enough surface area and pressure acting on it for things like marbles.

Honestly I think your best bet is a blow-forward bolt.
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Gun Freak
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Mon Feb 20, 2012 9:21 am

Oops :D

How about just a tee mag with a light detent?
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JDP12
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Mon Feb 20, 2012 2:59 pm

Jsr- for making a new piston, what about just backing the original piston with a washer? Or should I make a new piston by epoxying a piece of rubber to the washer
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Gun Freak
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Mon Feb 20, 2012 3:13 pm

If you back it with a washer, try to get one with the smallest hole in the middle. But I think that should suffice.
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