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Spear Gun

Posted: Mon Nov 21, 2005 7:38 pm
by Weasel
does anybody know how i could make a spear gun that will actualy shoot under water? i made one that shoots out of water quite well thats kinda just like a regualy combustion spudgun but im at a loss when it comes to building one that will actualy fire under water and work well. does anybody have any ideas?

Posted: Mon Nov 21, 2005 8:22 pm
by TalonXxX
it would have to be a pneumatic for sure :P
you would need to have a magazine with as many shots as you want to do underwater because you would have to fill magazine above water... you couldn't reload the gun underwater... also, the ammo would have to form a pretty tight seal in the barrel...

Posted: Mon Nov 21, 2005 8:51 pm
by Weasel
i already got the tight seal down. poured expanding foam down the barrel after i put the spear in so the ammo is air tight, i only need it to shoot once but i dont know how to set up the pneumatic stuff. iv kinda only done this stuff with combustion and i dont really have much money to spend on it.

Posted: Tue Nov 22, 2005 5:00 pm
by boilingleadbath
"it has to be really well sealing"
No it doesn't. You'll get bubbles anyway, and the couple feet/sec arn't worth much extra effort.

The issue I see is that your barrel will fill up with water, and adding large amounts of mass to be launched... but seeing as you say you only need 1 shot, it shouldn't be too hard to put a aluminum foil burst disk on the end of your barrel (in a union, of course)
It would be <i>possible</i> to re-load a shot underwater, but it would probably be fairly difficult. Or, you could make interchangable barrels with a union on each end... might have trouble with the line, though.

Posted: Tue Nov 22, 2005 8:15 pm
by Weasel
the barrel dosent fill up with water i have the foam filled all the way up and down and narrowed to a point at the end. the foam is really thick, it would be hard for water to get past it unless the thing was under water for a long time like 2 days. i just need to know how exactly i would set up the air tank to shoot it. i took my combustion test one and put the barrel down under water at a lake and shot it and it went really well but i know i wont be able to use combustion under water. i wish i hadent packed my camera up for my move or i would show you pictures of what iv got going on. my only problem is i need it to be air powered and the system needs to be set up so it will work in water. everything else i got covered

Posted: Tue Nov 22, 2005 9:19 pm
by TalonXxX
do a CO2 cartridge powered set-up with a relatively small chamber... that way you could use a very portable and non-bulky air solution and still get enough psi to launch it a good distance. 3" PVC at about 5.5" gets 100 psi with a 12g CO2 cartridge, just a thought... not sure exactly what you are looking for? how to build a pneumatic? plans for one? ideas? not too sure...

Posted: Wed Nov 23, 2005 12:44 am
by deathtodeer666
okay, okay the pnematic would work kinda good but if you wanted a good spear gun I would use a exposed spear on a rod with surgical tubing and a handle with catch, thats the way I would go.

Posted: Wed Nov 23, 2005 4:01 am
by Cronic
Ok you wouldn't be able to do that because it's just too weak to shoot under water. And even if you do it wouldn't be that good compared to other underwater guns that work on the principle of a piece of rubber shooting them out at high velocity. Not trying to be a party pooper so good luck with your project :D

Posted: Thu Dec 01, 2005 12:18 am
by pyromanic13
ya definently go with just a sling shot style