Pen Gun Questions?

Miniature guns are novelty custom, unique, and sometime downright crude! Common construction materials often include pill bottles or pens. Show us your work!
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clemsonguy1125
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Thu Jul 22, 2010 12:16 pm

I finally decided to try building another pen gun after the failure of my last. On my last the piston would seal but not pilot and it leaked terrible from where the barrel was attached. I don't have access to the "good" epoxy JSR uses, I can use the Devcon Epoxy they sell at Lowes or JB Weld. Which would be better for attaching the Schrader and barrel. The barrel will be a brass tube and the chamber will be a 7.14mm piece of brake line. I was planning to inject the epoxy that will hold the barrel in place using a syringe but are there any other ways. Also whats the best way to hold the barrel in place while the epoxy cures?
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jb weld.jpg
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The Epoxy I Access To
The Epoxy I Access To
devcon.jpg (27.5 KiB) Viewed 2415 times
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jor2daje
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Thu Jul 22, 2010 12:21 pm

I would find a round piece of plastic, aluminium or best brass, chuck it in a drill and turn with a file the O.D. to the I.D. of your chamber, and drill a hole the size of your barrel through the middle. The good thing about doing this while still chucked in the drill is that both holes are cocentric making your barrel perfectly centered in the chamber.

If you use plastic or aluminum you can use epoxy to join the chamber, this fitting, and your barrel, but if you used brass then you could solder everything together making a nice strong joint.
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SpudFarm
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Thu Jul 22, 2010 12:24 pm

I have seen JSR write something like: "Epoxy that cures fast has a tendency to have lower quality then the long curing stuff"

Also, I would hold the barrel centered using a washer that fits into the chamber perfectly and has a hole the same diameter as the OD of the barrel.
Never built anything like this but this is how I would have done it.
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Gun Freak
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Thu Jul 22, 2010 12:29 pm

Wrap the barrel with a skinny piece of tape until it fits inside the chamber, then epoxy it in to make it airtight, wait a few minutes for it to dry, then fill in the rest of it with JB Weld.
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clemsonguy1125
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Thu Jul 22, 2010 12:33 pm

SpudFarm-Ive heard JSR mention that but I cant find any better stuff locally, also Ill look for the washer it sounds like a good idea if I can get a hold of the right size

Jor2djae-Sounds like a good idea, the local hobby shop where I buy brass has brass rod, I just don't know how Im going to drill a perfect hole in the center without a drill press, would JB Weld work better for joining brass than epoxy
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Gun Freak
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Thu Jul 22, 2010 12:34 pm

Instead of using the brass rod just wrap the barrel with tape and then proceed to fill the space in front with JB.
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clemsonguy1125
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Thu Jul 22, 2010 12:36 pm

Doesnt JB weld come out of the tube as a thick paste, also does it do as ood of job of sealing as Epoxy
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Gun Freak
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Thu Jul 22, 2010 12:40 pm

Yeah it is a high viscosity but if you mix enough then use a toothpick or nail to transfer it to the front of your bushing thingy then it should work...
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clemsonguy1125
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Thu Jul 22, 2010 12:42 pm

I think it would work better to suck it up with a syringe and inject it into the tube.
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Gun Freak
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Thu Jul 22, 2010 12:43 pm

Ok that would work too. Good idea, but you'll want to clean the syringe right away.
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clemsonguy1125
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Thu Jul 22, 2010 12:44 pm

or throw it out, they cost like 10 cents, or I can just ask for freebies from CVS
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jackssmirkingrevenge
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Thu Jul 22, 2010 1:49 pm

clemsonguy1125 wrote:I finally decided to try building another pen gun after the failure of my last. On my last the piston would seal but not pilot and it leaked terrible from where the barrel was attached. I don't have access to the "good" epoxy JSR uses, I can use the Devcon Epoxy they sell at Lowes or JB Weld.
I made this one using Araldite only, which is equivalent to the epoxies you have, and in such a small diameter construction it was good to 800 psi without failure or leaks.
Also whats the best way to hold the barrel in place while the epoxy cures?
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Find a drill bit the same size as the inner diameter of your barrel, and wrap an end of it with tape strips until you reach the inner diameter of your chamber. Voila, centred barrel ;)
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clemsonguy1125
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Thu Jul 22, 2010 1:58 pm

Thanks, that's a great idea
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Lockednloaded
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Thu Jul 22, 2010 2:19 pm

I just put together a small co-ax, cant call it tiny without jsr posting a link to his pico-ax, held together with JB weld. I'll tell you how it goes when it cures
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jackssmirkingrevenge
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Thu Jul 22, 2010 2:22 pm

Lockednloaded wrote:cant call it tiny without jsr posting a link to his pico-ax
A search for "pico-ax" only yields 5 results :P ;)

Good luck with it :) how small is small?

I'm currently making one to fit into a Parker ballpoint:

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... nicked from my father's office, so it has to fit without modding the casing :roll: :D
Last edited by jackssmirkingrevenge on Thu Jul 22, 2010 2:25 pm, edited 1 time in total.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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