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M79 Idea?

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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M79 Idea?

Unread postAuthor: anhydrite » Thu Feb 15, 2007 8:14 pm

Im working on designing an M79 and need some advice/recomendations.

I want it to look like an M79....not an M14 like the ones online.

I want to shoot nerf footballs....the 2 inch kind.

I have it worked out on GGDT and I need to fit 50 cu inches into the gun somewhere. Any ideas.

Ill get 200 fps with 50 cu in and a 10 in barrell.

That leaves 4 inches of barrell space to put the valve. I need some place to put the chamber...I was thinking in the stock...but there pretty thin so not much room

Here is a pic of where everything would go
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Unread postAuthor: Killjoy » Thu Feb 15, 2007 8:21 pm

If you have good welding skills or know someone who does, weld steel into the shape of a stock for the air chamber.
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Unread postAuthor: chaos » Thu Feb 15, 2007 8:25 pm

yer that would be awesome or i you got tha cash get one pressure formed :wink: that would rule.

peace
chaos

ps: so wat if i diddnt use spellcheck, i had a marble in my hand last night.
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Last edited by chaos on Sat Feb 17, 2007 4:49 am, edited 1 time in total.
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Unread postAuthor: iknowmy3tables » Thu Feb 15, 2007 8:33 pm

it must be hard it intergrate a large air chamber like that into the stock, you could try one or two smaller pipe (it shouldn't matter if you use 12 gram CO2s) it going to be hard to not screw up the shape of the gun
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Unread postAuthor: alextheametuer » Fri Feb 16, 2007 5:55 pm

just use two tanks in the stalk and it should work pretty well
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Unread postAuthor: judgment_arms » Fri Feb 16, 2007 8:20 pm

I’m guessing this isn’t what you’re looking for…
My advice is to keep the chamber as small as possible, use high pressure not high volume.

Ok ran an idea of mine through the GGDT, will this be doable for ya?
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Unread postAuthor: iknowmy3tables » Sat Feb 17, 2007 2:58 pm

yeah, I agree, but if I were you I would use a QEV, and build the chamber in the forehandle
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Unread postAuthor: judgment_arms » Sat Feb 17, 2007 3:23 pm

Yes, exactly, or you could put it in the stock, ether way the only problem is going to be the valve. Piston valves are a bit too big, as are sprinkler valves, I don’t know about QEVs, and a ball valve is going to kill the looks.
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Unread postAuthor: anhydrite » Tue Feb 20, 2007 6:17 pm

Great advice.

Ill probly use a QEV and put the chamber in the forestock.

I may model it off of the HK69 instead and use the grip as chamberspace also along with the reciever section.

hmmm. Also if I use a smaller chamber size the 12 gram generates to much pressure so I need a way to only use part of the 12 gram.

Has anybody used those 12 gram things bikers use to inflate bike tires. Could those be used to fill up a chamber to a specific pressure using a guage to stop at the desired pressure. (how much pressure will a schreader valve hold back?)
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Last edited by anhydrite on Tue Feb 20, 2007 10:40 pm, edited 1 time in total.

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Unread postAuthor: anhydrite » Tue Feb 20, 2007 10:38 pm

OK.

If I put a 10 inch long 1-1.5 in chamber ill get about 10ci chamber.
Ill need a chamber and valve that holds 150psi. Ill also need a way to fill it to that pressure quickly. Im thinking of using a 12 gram co2 quick change hooked to a valve...like those used to fill bike tires.

What id like is some recomendations on chamber/valve combo that will hold those pressures +/- 20psi.
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Unread postAuthor: judgment_arms » Tue Feb 20, 2007 11:24 pm

Yes, you can regulate how much PSI the Co2 tire fill thing delivers, you’d have to be able to; otherwise it would just pop the tires.
It depends upon the Schrader, I’ve taken a brass on up to 120PSI with no ill effects, just ask the guy you buy it from if it doesn’t say no the package, do not use the “pop-in” variety
But I think, if you’ve got the money, you should get a beefier valve, one that can take the 400PSI, give or take.
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Unread postAuthor: rna_duelers » Wed Feb 21, 2007 4:38 am

A cam-lock burst disk gun!

No moving parts,no big valves and a lot of flow plus the barrel can be detached easily and even made to to look like a 'barrel cracking' mechanism.
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Unread postAuthor: judgment_arms » Wed Feb 21, 2007 12:52 pm

Rna, you’re a genius.
There’s still the small matter of triggering the burst disk, he’ll need to be able to fire the gun on a whim, and more importantly, what should he use for a burst disk, something that bursts at about 300-400PSI… hay, how about a piece of DWV?
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Unread postAuthor: iknowmy3tables » Wed Feb 21, 2007 2:16 pm

thats a good idea, the activation of the quick charge will trigger the gun, I wonder if anyone has done this it fixes the problem with burst disk pneumatics actuating when you choose.
I never used a quick charge, (arn't they activated buy twisting the slevee?) so put it in the grip, and twist, it might look alittle strange, but I bet you can fix it it look decent

also some thing I hope can be helpful. use a long and large drill bit and cut holes for the chamber
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