Hey you guys this is going to be my Pen cannon when it's built

. So I have 3 different barrel sizes 2 are long that i got from school and the largest one is from my bb gun. For the shredder valve I have a tire valve. That I will shave the rubber off so it's just the metal. The piston I'm still not sure on :/ to get it tonthe right size and to last because it won't be servicable. Another problem is I can only fill it up to no more than 200 psi.
Alright enough of my dum blabiling here are some picture od the barrels. And the pen I would use if I am to use the 2 smaller barrels.
Oh and i'd use epoxy to hold the valve and epoxy at the end. Supported?

That's the wholes the pen has I'd cover them with jb weld

Bb gun barrel
Thanks
