SpudFiles

I wanted to make a Single-Shot Pneumatic BB Gun and now I'm wondering how i could link the tiny barrel to a ball valve. It should be possible to load it without unscrewing the barrel, but with another tube sliding above the barrel to seal it.

Does anyone have a diagram for such a setup?

Greetings,
Pete from Germany

You could use a quick connect thing for compressors, but that may be a little more bulky that what you want.

For bb's the best thing is something that slides over a hole cut into the barrel. I used a coupler and sanded the ring out that way it would slide over the pipe. Your problem is finding a coupler that is 6mm, which to my knowledge does not exist.

You can look at a hardware store for brass pipe that fits around your barrel. Each tube size fits inside the next size bigger, so if you get a 1/4" barrel (6.35mm) you can but a slice of the next size up and it will fit perfectly over it.

I've got another idea: I take a 10x2mm, 12x1mm and 15x1,5mm pipe (ebay). Then stick them into each other.

The inner is the barrel, the next will be for sealing and over that there is the outer pipe, like this:
http://img846.imageshack.us/i/unbenanntbk.jpg/

But how to attach them? Do they are such precise that they will be tight together when they are sticked together with one pipe warm and the other cold? Or is there another way?

And then the ball valve has to be connected, so a threat must be cutted. Is the size of the pipe equal to outer threat of the same pipe? Or is there a "loss"?

Or overall is this to complicated? I wanted to have a "load chamber" with a slider over that and a clean outer piper, so it looks like smooth. The outer pipe then has to be connectable to a ball valve.

what kind of material are you going to use and what diameter will the piping and valve be? I would suggest epoxying the barrel to the inside of a
1/2 <-> 1/4" adaptor fitting like this one http://www.bellpro.net/xcart_program/pr ... 271&page=1. depending on how large you want the resovoir/valve to be you can use any number of adaptors or reducing bushes http://www.bellpro.net/xcart_program/home.php?cat=275 joined in sequence.

the "tube sliding above the barrel" is known as a breech loader (I think). they are used on many of the cannons on this site
http://www.spudfiles.com/forums/first-f ... 22401.html
http://www.spudfiles.com/forums/snowy-s ... 22094.html
http://www.spudfiles.com/forums/basic-b ... 21619.html

for your purposes I would use the closest possible diameter tubing above 6mm (e.g 7 or 8 mm, I'm not sure about German standards)

I apologize for the crappy paint drawing but here's a basic idea

http://i762.photobucket.com/albums/xx26 ... lvalve.png

good luck!

Are epoxy conenctions that strong?

you could use compression fittings, thats what i always use.

If you make sure to roughen up your barrel, yea they are very strong. Jsr a member on this forum has taken his epoxy creations to 800psi pneumatically, and made 16x hybrid, which at around 1500 psi.

Crna Legija wrote:If you make sure to roughen up your barrel, yea they are very strong. Jsr a member on this forum has taken his epoxy creations to 800psi pneumatically, and made 16x hybrid, which at around 1500 psi.

A little more than that

Okay, now I've got another qquestion.
A ball valve lets all the air out, but for such a little bb you only need a small amount of air. And I don't want to fill it up after each shot.
How to achieve that?
With an air pistol like my father uses to blow the dust away?
Would that air be strong ang enough to accelerate the bb like a ball valve but without the loss of all the air?

Pete wrote: ball valve but without the loss of all the air?

yes

So my idea of using an air pistol was right? But how much air/power comes out of such a pistol? Or is it adjustable?

have a look at this test, with 110 psi from a compressor and a long barrel it will put a pellet through a tin can.

You might also like this one:

http://www.spudfiles.com/forums/semi-fu ... 22088.html

Thank you for the links They helped me a lot!

Ehm do you know how much air goes out of a blowgun or how large the chamber has to be for a certain amount of shots?

Pete wrote:Ehm do you know how much air goes out of a blowgun or how large the chamber has to be for a certain amount of shots?

First of all, a blowgun doesn't let out a fixed amount of air - it depends how quickly you pull the trigger, and for how long you hold it.

Secondly, how many shots a certain chamber size will last also depends on how much pressure you take it to. A large chamber at low pressure will probably last less than a small chamber at high pressure.

I think you need to define some requirements first:

- what kind of power are you after?

- how many shots do you want before you need to fill the chamber again?

- how big do you want to make it?

- how much money do you want to spend?

- what facilities do you have for filling the chamber (bicycle pump, paintball tank, shop compressor etc.)

Give us these details and we can give you a better idea of what to build and how to build it