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Coaxil Piston air rifle(Design ideas, are they sound?)

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Coaxil Piston air rifle(Design ideas, are they sound?)

Unread postAuthor: Happy » Tue Feb 19, 2013 5:46 am

I have a project in mind this is my project.

A copper coaxil piston air rifle.
It will consist of a 3/4" barrel and 1 1/2" chamber.
Barrel lenght: 45cm
Chamber lenght:20cm
Pilot lenght:5cm
Ammunition: Corks and Cork sabots (probably try out different fillings for the sabot)

30 cm of chamber and barrel (cumulative) will be placed in a wooden case acting as a body and stock. The wooden casing will be standard rifle style.

The chamber will be reaching up to the back of the wood body were one of two shcrader valves will be uncovered by wood so i have the option of using a compressor. The other shcrader valve will be connected to the blow gun hidden by the wood.

A shock pump will be under mounted on the wooden body of the rifle connecting up to the covered schrader valve though the tubes will be hidden in the wooden body.

The chamber will have a threaded tee installed, the tee does not add lenght to the overall lenght. A pressure gauge will be installed on the tee.

The piston will be a simple washer and rubber, setup on a small bolt.

Now for the part im most worried about, the magazine.

My idea is to use a tee that is on an angle of say 45 degrees to feed corks into the barrel, the force of the blow guns pilot will push the corks down.

The tee will be installed on the barrel, a 3/4" pipe will then be soldered onto the tee and a threaded cap installed.

The cap will be connected to the blow gun nozzle were a regulator will be. (i have no idea how to do this btw)
The regulator will take the pressure and convert it to a lower pressure so the corks will not move straight away ones the rifle is fired).

Also inside the tee there will have to be a piece of stiff rubber covering the hole where the corks will be seperated from the barrel, it will have to be slightly larger then the hole so as not to blow up into the magazine.

I have no idea if this setup will work. I have researched about as much as i could but didnt find many topics on magazines. I would humbly ask for your advice and profusely apologize for waisting your time.
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Unread postAuthor: jackssmirkingrevenge » Tue Feb 19, 2013 6:57 am

A picture would be a lot more helpful :)

If I understood correctly, you want to push the projectiles from the magazine using the pilot volume?

Also, as this is not going to be a repeater, I don't see why you should bother with a magazine.

An alternative would be to make a hole in the barrel covered with a sleeve, something likethis golf ball launcher:

Image

Image
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Unread postAuthor: Brian the brain » Tue Feb 19, 2013 12:27 pm

You could go the "partly coaxial"route.

A coax around the barrel, then a T and a loop running back up to a T in line with the first one.
With the barrel pointing down it would resemble the letter P.


The barrel runs through the first T and ends in the second.
This exposes a section of the barrel between the two T's wich could be used to breechload.

The sleeve JSR suggested would work well.
You could build a magazine inside the "loop" under the exposed barrel section.
Another option would be the blow forward valve or bolt wich JSR could link you to...

But..as long as it's not hooked up to a compressor or some type of tank a magazine is not worth the effort nor the jamming issues you might experience.
A coaxial is usually a single shot , muzzleloading type deal.
Simplest is often best.
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: Happy » Wed Feb 20, 2013 4:35 am

Thx guys I guess i was getting ahead of myself. I saw in one of the pneumatic showcases someone made a sniper rifle that was breach loading with a mag. I thought i might give it a shot and came up with that extremely fiddly plan.

Though I like the idea of a semi auto it would be extremely silly I guess. Awell I guess i will have to play with this idea at a later date perhaps after my next prject :D

Also a link to a post of a breach loader with a mag would be nice but i cant for the life of me find one.
p.s I cant make my cannon yet because i only just got a job and im still waiting to clock up hours to by parts :\ sorry bout that.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 20, 2013 8:28 am

wyz has a good tutorial: http://www.youtube.com/watch?v=RKpeHUsa5vw

If you buy cheap-o chinese parts from eBay, you really don't have to budget much for a decent and powerful build.
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Unread postAuthor: Happy » Fri Feb 22, 2013 3:51 am

Omg thank you for the vid that blow forward bolt is awesome!

Also this will be my first metal build and i wanted to make it special i also dont have an ebay account cause im useless like that.

Oooh ooh I wonder if i could place that blow forward bolt in my coaxil! I could place it in-side the chamber in line with a tee so the magazine sticks out!
...But im shooting corks :( so maybe next time.
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 22, 2013 5:20 am

This was my first: http://www.spudfiles.com/forums/6mm-sem ... 10075.html

I strongly suggest buying parts online, the savings are simply ridiculous compared to local purchases if you are prepared to wait a few weeks.
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Unread postAuthor: Happy » Fri Feb 22, 2013 8:48 am

Thx I just might and hopefully i can get my gun together and upload some pics to add to the data base.
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