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6mm pellet launcher

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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6mm pellet launcher

Unread postAuthor: Deceiver » Mon Apr 19, 2010 12:25 am

I started out to make a 6mm launcher last summer and it fell to the wayside shortly after it's beginning. The parts lived in my closet for nearly a year before my interest and funding permitted me to complete the project. This is the result.
As you can see it's a simple barrel sealing T-valve triggered by a blow gun. The only modifications to the blow gun were to remove the OSHA approved nozzle, grind off the finger loop, add some thread sealant to the valve body and to epoxy the blowgun to the brass T connecting it permenantly to the launcher. I had to do this in order to get the threads to seal in the orientation I needed them in.
The barrel is made from an 18"(it's actually 19.5") section of tubing for sink/toilet repairs with roughly a .24" ID(OD 3/8") . The piston is cast epoxy with red valve repair rubber(sold in 6x6" squares) superglued to it.
The resevoir is ~8.5x1/2" sch 40pvc. I cut down the T and elbows to reduce the form factor and then placed 6 #4x1/4" screws and then the joint is smothered in epoxy. I need to add some more due to a pinhole leak that has developed.
Everything is glued together, so if anything catastrophic happens I'll have to rebuild the entire launcher and may be unable to scavenge any of the parts. But due to the low price of small diameter pipe I'm not too concerned. The most expensive part is the blowgun, which would probably be removable, although a bit time consuming to do it gently.

The foregrip is friction fit to the air chamber and barrel with a piece of 12ga fencing wire serving both as a barrel pin and a front sight. The stock is attached to the foregrip by 4 machine screws with nuts epoxied into both sides but these are the only bits of hardware holding the launcher to the stock. While not amazing robust, I'm not planning rifle butting anyone with it.
The wood work could have conceivably be done with no power tools if you had a handpowered drill/auger on hand as it was largely shaped by a chisel and hobby sized plane. It is varnished to protect against water and such.

In the future I may attach some sort of proper optic, but for now I the longest range I've been able to shoot at was 12ft. It still had the oomph to punch through a soda can bottom at that range too.
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Attachments
6mmrifle2.jpg
6mmrifle2.jpg (16.71 KiB) Viewed 2143 times
thumbhole.jpg
Lovely grain
thumbhole.jpg (38.92 KiB) Viewed 2143 times
filling.jpg
This is a picture I took before I completed the finishing touches, it just displays how the shock pump connects through the stock to a schrader valve mounted to the back of the valve
filling.jpg (26.48 KiB) Viewed 2143 times
canbottom.jpg
according to ggdt this was only <40 psi
canbottom.jpg (8.51 KiB) Viewed 2143 times
cantop.jpg
Based on the Redwolf airsoft poor man's chrony table and ggdt predictions this was fired at <70psi. the 180 is the number of pumps. I beleive when this shot was fired I hadn't greased the blow gun, so it still leaked like a sieve.
cantop.jpg (26.73 KiB) Viewed 2143 times
Last edited by Deceiver on Mon Apr 19, 2010 12:58 am, edited 1 time in total.

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Unread postAuthor: jackssmirkingrevenge » Mon Apr 19, 2010 12:36 am

Very nicely put together, kudos. How small calibres however, I would advise against low pressure high volume, get yourself a shock pump and some metal fittings and you'll be amazed by the difference in performance.
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Unread postAuthor: Patto » Mon Apr 19, 2010 4:29 am

looks good man i like the stock 8)
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Unread postAuthor: chinnerz » Mon Apr 19, 2010 5:53 am

yeah man that i a bloody awesome stock. also i see you arnt using the bottom of the blow gun, why not cut it off after the valve.
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Unread postAuthor: Deceiver » Mon Apr 19, 2010 4:17 pm

I am using a shock pump(rated to at least 250 the packaging is a little vague). The main reasons I haven't taken it to higher psi is 1) there are a number of leaks I need to fix 2) the pump is extremely low volume so it takes hundreds of pumps to get high pressures.
I used limited metal because I have no plans(or money) to take it into the HPA realm and 1/2"pvc can still handle 600psi, even factoring in my modifications it should be able to handle 3-400. Which with airsoft pellets(+0.2g) or #4 buck(1.34g) will put out respectable fps at 250psi (914 & 470 ) and ft-lbs( 5.7 & 10.1 ). These pressures are also above what most commercial shock pumps are rated for.

As of now I'm pretty happy where it's preformance is, it's just for plinking and perhaps persuading racoons and possums to go mess up someone else's garbage.

Some of the specs I forgot to include in the original post are:
Chamber volume:2.583 ci
Barrel: 19"x.24"
Primary ammo: 6mm 0.2g pellets
max energy efficiency:7.9% @ 20-21psig ( assuming I have everything input into GGDT accurately)
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Unread postAuthor: clemsonguy1125 » Mon Apr 19, 2010 4:23 pm

I use the same barrel, there cheap and easy to get but are flexible
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 19, 2010 5:03 pm

Deceiver wrote:the pump is extremely low volume so it takes hundreds of pumps to get high pressures.


That's the point of using shock pumps though, in general a smaller chamber at higher pressure will give you more power, even for the same amount of air (eg 10cm<sup>3</sup> chamber at 50 psi vs 5cm<sup>3</sup> chamber at 100 psi) - have a look at this GGDT exercise to get an idea - and proportionally your chamber is far too big for a single shot launcher. Thisis the sort of performance you can get from small chambers and high pressure ;)

Not trying to knock your design, it's certainly very well made (I'd applaud epoxy construction anywhere :D), but with a little thought and less financial outlay than you think, performance can be optimised.

These pressures are also above what most commercial shock pumps are rated for.


Mine is rated for 400, love it to bits :) cheap too, highly recommended!
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Unread postAuthor: Deceiver » Mon Apr 19, 2010 5:37 pm

You and your super shock pump! 8) Oh I know the air chamber is far too large(and inefficient) for the barrel size, but I don't have anything to get into the more efficient high pressures. I'm envious of the power of your burst disc launcher.
Although maybe in the near future I might lop off a couple inches of air chamber. A quick number crunch says .608ci @ 200psig should put out 708 fps and 3.4 ft-lbs.
Although I'm a bit attached to the possibility of 10ft-lbs coming from the massive 8.5"(2.6ci) air chamber on it now.

The barrel flex is counteracted by the foregrip and held down by the front sight. It seems to be pretty consistant and at the short distances I've been able to test it at have been 11ft and I've had to aim like 9" low to hit my target. Perhaps at farther ranges the hold-under will be more reasonable.
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 19, 2010 5:48 pm

Deceiver wrote:You and your super shock pump! 8) Oh I know the air chamber is far too large(and inefficient) for the barrel size, but I don't have anything to get into the more efficient high pressures. I'm envious of the power of your burst disc launcher.


With a bit of careful use of epoxy, a high pressure launcher isn't too difficult to make. This design can be put together in an hour with basic tools (power drill, hacksaw etc.) - if you stretch it out, you'll have a powerful rifle that will safely take over 500 psi, and you clearly have the ingenuity to make a simple lever trigger to operate the schrader pilot.
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Unread postAuthor: Deceiver » Wed Apr 21, 2010 11:21 pm

Here's an update now that all of the main leaks have been filled with epoxy. http://www.youtube.com/watch?v=Zj9jMqjbcgg There's a description on the video's page but here're the cliff notes:

The .2g 6mm pellet was launched from ~3 feet away at the bottom of a 1lb coffee can, which it had no trouble penetrating. The hole it left was smooth and had no ragged edges, which leads me to believe the pellet had substantially more energy than was required to penetrate the can.

The backside of the hole was perfectly uniform, a follow up shot later was not as clean, a small tear-out from the center formed with a perfect negative of the pellet before it stretched the can to the tearing point.
http://www.youtube.com/watch?v=BPp9Cb88sYc
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Unread postAuthor: chinnerz » Thu Apr 22, 2010 12:31 am

lol @ the subsonic AF motor in those vids :)
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Unread postAuthor: Deceiver » Thu Apr 22, 2010 12:06 pm

yeah, It's a nikkon 4100 which is why the quality is lacking. That autofocus is so annoying. The battery door is broken too, do they even make cameras that have removable batteries anymore?
Although now that I've fixed the big leaks in all my pumping I've loosend the seal around the tirevalve so sometimes when I'm pumping I release some air.
Overall I'm pleased with the preformance, except now I need to figure out some pellet retention system so I can aim at things below horizontal.
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Unread postAuthor: jackssmirkingrevenge » Thu Apr 22, 2010 3:04 pm

Deceiver wrote: Overall I'm pleased with the performance, except now I need to figure out some pellet retention system so I can aim at things below horizontal.


You can simply file a small slot in the barrel and slip an o-ring over it, and epoxy the whole thing in place, or you can be a bit more elaborate.

Either way, it shouldimprove performancesomewhat ;)
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Unread postAuthor: Deceiver » Thu Apr 22, 2010 8:48 pm

Yeah but then I'll have to turn it into a breech loader. Which while not a bad thing overall, would turn into a bigger project than I'd like.

After a 4 year hiatus I've fallen off the launcher wagon. I've already been thinking up pistol sized designs. I've been especially inspired by some of the commercial designs with an integral pump where one stroke gets you +400fps.
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Unread postAuthor: Stolly32123 » Thu Jul 08, 2010 7:43 am

it needs some pics of just the gun itself. (without the wood)
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