SpudFiles

I have been thinking about Pneumatic air guns for a while now and discovered this beauty of a forum only yesterday. I have been putting off making my cannon for ages because of my inexperience and ignorance of measurements and metal work but after looking through 140 pages of Pneumatic cannons I have been inspired to further my interest and create my own 'Pneumatic air musket', or rifle if I somehow manage to obtain a rifled barrel. This topic will contain what I want to build and a few general questions.

At the moment I am only interested in Pneumatic small caliber (6mm - 15mm maybe) guns with a decent amount of pressure because I obviously want my cannon to shoot hard and fast.
I am visualizing a very simple design, 250mm of 1" steel pipe which connects to 1/4" copper U-bend pipe then to a QEV valve then to 500mm of 6mm copper pipe which would be on top of the 250mm x 1" air tank.
I don't know shit about working with metal so I am not particularly sure when to use metal fittings and threads for connections or when to solder. I was originally going to just use a ball valve but saw that everyone shunned it for not being operable for high PSI so I guess I'll use a QEV valve (I am still trying to understand how this works, if anyone has the patience to explain that would be great). Not sure if I should make my own or just buy one from ebay.
I will be making my own wooden stock and I want the gun to be comfortable and to actually look like a rifle so I don't want big bulky air tanks.
I want all of the pressure from the tank to be used for every projectile, I don't want to concern myself with pilot valves and whatnot.

Questions:

1: How do QEV valves work? (don't shoot me pls)
2: Why do people muzzle load/ram rod when they can cut out a hole at the back of the barrel,load the projectile then cover the hole? Is it because the hole weakens the structure of the barrel? Surely a leaking 2% of the air would be worth twice the reload time.
3: For my design, should I be using copper, brass, steel, aluminium?
4: Would 6mm steel ball bearings be the best projectiles? When would the magnus effect take place, 5ft, 10ft, 30ft?
5: What wood should I use for my stock? I was think balsa wood, maybe its too soft/weak.
6: Are metal pipes, threads and stuff PSI rated? Can I just chuck them together, look at the lowest PSI rated item and put in whatever the PSI rating was into my tank.

Any criticism, information, advice and verbal abuse for my ignorance is welcome.
I live in Australia so if any Aussies can point me in the direction of local hardware stores for this then that would be great.

sounds like you have a plan, that's a good start.

lol
1: no comment... I'm sure abuse is to follow... and look forward to pilot valves and whatnot;)
2: good points... and when you start building breech loaders you will know the answer
3: use what you have or despair
4: best for what? I think you will not notice Magnus effect until 30' or more
5: Balsa is too soft. You can harden it with various polymers but it's easier to start with something like structural lumber, or wood flooring glued together
6: pretty much

Anatine Duo wrote:lol

3: use what you have or despair

That's my whole ethos

Why do people muzzle load/ram rod when they can cut out a hole at the back of the barrel,load the projectile then cover the hole?

Usually because it's easier to muzzle load than to create a breech loading mechanism and most people don't mind the slower reload rate.

Would 6mm steel ball bearings be the best projectiles? When would the magnus effect take place, 5ft, 10ft, 30ft?

Magnus effect is for airsoft, aim for high velocities with projectiles made of dense materials like lead.

What wood should I use for my stock? I was think balsa wood, maybe its too soft/weak.

On its own, yes but with a bit of epoxy + glassfiber can turn it into a hardwearing and light stock.

QEV explanation from the wiki: http://www.spudfiles.com/spud_wiki/inde ... aust_valve

I was originally going to just use a ball valve but saw that everyone shunned it for not being operable for high PSI

You can use it with a spring-loaded mechanism: http://www.spudfiles.com/pneumatic-cann ... 23034.html

http://woodgears.ca/airgun/

I had a dream last night of someone showing me there breech loaded cannon...weird huh?

I have no idea who the person was, but the breech was huge..anyways just thought i'd share my pneumatic dream with you all.

Hehe

Just a comment, but the 1/4" copper that connects the chamber to the QEV will severely restrict airflow. This means the performance won't be nearly what it could be if the chamber was connected directly to the QEV or via a much larger connection.