As you probably understand the problem here is that the captive piston has to be stopped almost instantly at the muzzle... this means there is a lot of stress acting on the barrel, the muzzle attachment designed to trap the piston and the captive piston itself

This method has one additional ...

POLAND_SPUD wrote:a captive piston is just a sabot that travels with the round along the barrel and then is stopped at the muzzle.... therby trapping the gases

Kinda..... hard to do with PVC isn't it? Cool tho.

Uh.... uhmm. Those look a bit complicated for me. and rather integrated.

:D

An integral suppressor would not be bulky.
Neither would a captive piston...
Or a fast resetting valve...

A longer barrel would up performance and accuracy and reduce sound.
Are we talking pneumatics here? I use this for a combustion Mini-Medium. Suppressors are pretty bulky for mine. But ...

Pros:
>This round is made up of a solid ammo and a cardboard tube tail, with slits cut in it. It can be made of any semi-flexible sheet rolled into a tube, can be any size. Only needs some tape otherwise.
>When shot, pressure can be released from these slits when the round exits the barrel ...

Alrighty so I've shot quite a few loads out of it. Its a very good fuel, and at this concentration, it doesn't seem like any damage. My gun is made almost completely out of fittings rather than pipe, and the fittings are still clean and perfect while the pipe looks a bit irregular inside. This leads ...

So i bought some denatured alcohol. It has 1-4% methyl isobutyl ketone. Would it damage pvc or pvc cement?

Oh and spuds are low density projectiles. A high density projectile such as a magnetite slug needs a slightly higher C:B ratio. Use a sabot for stuff like that!

The reason that a large chamber can damage performance is if the fuel does not burn fully before the projectile leaves the barrel, so not all the available energy is converted to pressure quickly, lowering psi. However, small chambers do not have enough fuel to burn. If you can get multiple ignition ...

Well as for the chamber:Barrel ratio, I like to stay within 6:1 and 2:1

Anything above 1:1 is going to be bad for performance, for a combustion you want the chamber to be between 0.9 and 0.5 times the barrel volume.

With pneumatics, bigger chamber = more performance, although to a certain degree ...

Okay so I am currently in the process of making my third cannon. My first was the basic potato cannon with hairspray and a piezio bbq igniter, then I made a small pneumatic, and now I am making another combustion.

I have a few questions.

1) Will a propane torch work well as a spray and pray ...

thanks imma try that tommorow

I had to put a screw into the PVC chamber, and I will seal it with epoxy. How should I go about doing this? should I sand the inside of the chamber hole as well and where should I dab the epoxy?

Here's how I would have gone about it, with the High Standard HS-10 in mind:

- full length suppressor packed with steel wool

- compact bullpup configuration, maximum barrel length for minimum overall length

- fancy AR ignitor grip from USG

- smaller chamber:barrel volume ratio to keep power up ...

why not make it like this
I though about that, but I decided I wanted the wye to point up instead for aesthetic purposes, as well as not having to attach both a stock and a handle.
Also note that the cannon is a breech loader and the handle would interfere with that. the barrel screws on and ...