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Finally something I call finished

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Finally something I call finished

Unread postAuthor: Tep » Sun Mar 15, 2015 9:06 am

I've been tinkering with plumbing parts for a couple of years now and until today I haven't come up with anything that I would call an actual finished product without major drawbacks. Most of the things I've made have been ridiculously complex, hard to actuate, horribly inaccurate, slow to reload and / or just generally annoying.

This gun was my way of going back to basics properly and in the process I made something awesome using easy to get parts from ebay, some brass fittings / tube, a piece of wood and a little bit of epoxy (could be optional).


close up of main bits

Anyone wanting to replicate this setup could do so with almost no tools. Wood saw, screw driver, scissors and shifting spanner would do it (pliers and soldering iron would help but optional).

It uses a off the shelf QEV, piloted with a cut down Schrader valve which allows filling from the chamber and super small pilot volume (<0.4ml). Chamber volume is about 20ml but maybe a little more depending on the volume of the fill line.

The Schrader is operated by an ebay bought solenoid (5nm force at 12V). The solenoid only just contacts the schrader so there is maximum force delivered by the very end of the solenoid stroke; it is powered by 8 AA batteries (this is overkill it can operate fine on a 9V battery which is about 1/4 of the size but I didn't want to take any chances.


The barrel / breach is a blow forward setup that I have cloned from another gun I posted, with a few improvements, it is now fully silenced and more accurate thanks to some tweaks it is also capable of (semi) semi auto with a magazine tube added.

Loading hole...

View from the front

It's got a red / green dot scope from ebay ($20 AUD) that had no problem clearing customs into Australia (the un-fun country) if anyone is wondering.

Scope picture

There is a ghetto safety built in to the firing mechanism that just stops the hammer from moving forward far enough to hit the schrader pin.

Hammer / ghetto safety

The whole thing is wrapped in rubber from a bike tyre inner-tube both for increased ghetto looks and to hold all the parts together. I had also included the barrel in the wrap earlier but it looked a little bit too realistic and I had visions of the cops shooting me on sight.

It shoots 8mm steel balls, at 100psi it will go through about 6 - 8 layers of cardboard so not super powerful but I wanted this for target shooting out to about 10 meters. It will handle +300 psi but the hose that I use to feed it bursts after much more than that.

Shot placement


Yes it does..

Ten rounds at 100psi from 7 meters (bench rest, indoors).
10 rounds at 7 meters

Question time:

Anyone have any ideas about how to make a mag for this thing that doesn't just stick out on a 90 degree angle? I can't

Would it be beneficial to the site for me to do a thorougher "how to" for this? I don't see many complete guns in the how to section is that not normally done?
Regards to all

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Re: Finally something I call finished

Unread postAuthor: Brian the brain » Tue Mar 17, 2015 2:51 pm

It's hard to tell because of the ghetto wrap... :D but a revolver type cilinder, revolving around the reservoir ( if indeed it is located under the barrel..???) would work if made correctly...

A complete how to is always appreciated....not just because I can't tell how it's built...
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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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Re: Finally something I call finished

Unread postAuthor: Tep » Wed Mar 18, 2015 8:15 am

I just realised that doing a how to for this would basically be like telling someone how to fold a paper aeroplane, there really is nothing to it.

I'll upload a schematic drawing when I get a chance to do one but in the mean time here is a picture of it with reduced ghetto wrap (ironically making it look far more ghetto...) I'm also running a 9V battery here but will be switching to something else again soon as the 9V is far too weak to operate the firing pin.

No wrapper...

Solenoid at back -> female to female pipe fitting -> schrader valve -> QEV ->

Blow forward barrel / bolt assembly

The bolt is hollow but blocked at the back by the glue stick. the force of the air blows it forwards sealing the loading hole in the barrel just as any blow forward would. Even though it is not a sealed system the force of the air is so great that it moves the bolt forward anyway.

bad pic of barrel / bolt housing

Bolt go's in here and the adaptor holds it in place.

Simplest idea in the world...

Magazine has been added in a hopper style (bit of half inch polly with two holes drilled in it holds about 55 x 8mm steel balls.
A magnetic detent makes sure there are no double feeds.
I've fired about 500 rounds and not one mis feed or failure to feed so I'm pretty impressed.

I've got an air supply sorted but have a question for anyone who is in the know:

The opening time on the schrader valve is super quick, I estimate <10/th of a second, but with a constant air feed into the chamber I loose a lot of air between shots. The gun makes a shooooosch noise as the piston reseats after each shot (as opposed to a honk). I can totally negate this by kinking the feed hose between shots but that seems an inelegant solution even though it saves me a lot of air.

I tried drilling out a hole in the piston which might have reduced the problem a bit but power really suffered I think because the piston was not fully opening as the schrader evacuated air too slowly. I refilled the hole with glue and it's back to normal, should I try to make a smaller hole??? I used a 1mm drill bit for the original hole.

Anyone who has successfully modded one of these Chinese QEV's will know what I mean. (yes I have a spring in there behind the piston...)

Opinions welcome.

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