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The ISM, Piston Valved MB Gun

Posted: Mon Apr 21, 2008 8:11 pm
by bigbob12345
Well I have been wanting to make this cannon for months. It was designed 3 months ago and I didnt get around to making it until now.
I name it the ISM or It Shoots Marbles

The gun
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Specs:

Chamber:42in of 1in sch40pvc.
Barrels:54in of 1/2in sch40 pvc(batteries), 60in of 1/2in sdr21(marbles, paintballs).
Valve:Barrel sealing piston valve in a 1in tee with a 1/2in porting.
Piston:Cast hot glue with a 1/4in neophrene sealing face and a small piece of a nerf ball for the bumper.
Pilot:3/4in modified orbit watermaster sprinkler valve exhausted by a blowgun.
Fill setup:1/8in threaded schrader valve
Pressures operated at:Normally 60-80psi as it is quite loud at higher pressures and would'nt want to disturb my neighbors. I have taken it up to 140psi but no higher than that until i can get to use it at some secluded place.
Ammo used:Mostly marbles and paintballs but I do shoot batteries and homemade heavyweight slugs every now and then.

In the making of this gun I cracked 2 different fittings from overtightening. One is the threaded adaptor that leads to the stock and the other is the threaded side of the tee the piston is housed in. Both were replaced rather quickly bacause I to shoot it, BAD.

GGDT says it is capable of 800fps(with light ammo)and over 200ftlb(with very heavy ammo. I dont know if that is very accurate because Im too lazy to go GGDT it again and I cant remember what it said very well.

I am very pleased with how this gun turned out. It works reliably, well, and packs a serious punch.
Also the pump up time isnt too bad which is very nice.

Here are a bunch of pics

The ISM from a couple different angles
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The piston valve
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The 3/4in sprinkler pilot
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The barrel support(tape will be replaced with a hose clamp)
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The "stock" for shoulder shooting
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I will give it a paint job tommorow(dark green) and possibly take a vid.

Ill have damage pics and pics of the piston up in a jiffy.

Posted: Mon Apr 21, 2008 8:38 pm
by ghostman01
wow thats one big gun ! woooooo first post! very nicely made

Posted: Mon Apr 21, 2008 8:42 pm
by STHORNE
nice job bigbob. damage pics? video?

don't be slackin' on such a nice gun bigbob....lol

job well done!

Posted: Mon Apr 21, 2008 8:53 pm
by elitesniper
haha, nice plinker, but couldn't you just put a marble barrel on your other piston gun, saving you some money?

Posted: Mon Apr 21, 2008 9:07 pm
by bigbob12345
Thank you for the comments
wow thats one big gun
Im going to have to disagree with you there, the chamber volume is only 40ci :lol:
But it still very powerful
damage pics? video?
don't be slackin' on such a nice gun bigbob....lol
Well damage pics are going to have to wait, along with a the vid because my piston crapped itself(broke in half :roll: ) while I was shooting a few things for damage pics.

I wont get it fixed till the weekend :(
haha, nice plinker, but couldn't you just put a marble barrel on your other piston gun, saving you some money?
:roll:


Edit: Haha not to many veiws or comments, too bad :( I really like this gun

Posted: Sun May 04, 2008 10:04 pm
by taytayswims
what is the size of the nipple used for the trigger system?

Posted: Sun May 04, 2008 11:22 pm
by bigbob12345
If I know what you mean, 3/4in

Posted: Mon May 05, 2008 7:25 am
by JDP12
seriously taytay?? You've gotta stop it, that's the second time you've asked that at least that i've seen.

Posted: Mon May 05, 2008 6:31 pm
by taytayswims
ilovetoblowthingsup wrote:seriously taytay?? You've gotta stop it, that's the second time you've asked that at least that i've seen.
i have only asked once but my cousin has been using my account sometimes and he has been commenting people and posting all kinds of non-sense i got him to stop and im sorry for wasting peoples time

Posted: Mon May 05, 2008 6:36 pm
by bigbob12345
taytayswims wrote:
ilovetoblowthingsup wrote:seriously taytay?? You've gotta stop it, that's the second time you've asked that at least that i've seen.
i have only asked once but my cousin has been using my account sometimes and he has been commenting people and posting all kinds of non-sense i got him to stop and im sorry for wasting peoples time

just dont have your account automaticly come up and then he wont be able to mess up your account.