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Gas Sampling Cylinder Paintball Cannon (Blowback)

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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Gas Sampling Cylinder Paintball Cannon (Blowback)

Unread postAuthor: Tetsuo315 » Sun Apr 11, 2010 1:49 pm

Well gang,

It's been a long time since I posted a new cannon so here goes. This cannon was inspired by a number of different sniper and competition rifles, so let your imagination choose what you think it looks like. One of the things I wanted to incorporate into the project was a bolt action cartridge fed system. I found that the CPVC was where I found my solution. As it turns out the 3/4" CPVC fits almost perfectly into 1" CPVC. This is how I achieved my bolt action system. I also wanted to go with a bullpup design, in that the cartridge would be fed into the breech from behind the sprinkler valve and blowgun. This would allow me to not have to reach way out in front to load and unload and it would be closer to my face. For this to work meant that I would have to use a T fitting that had to be customized. See the pictures below for details. This cannon also has blowback. There is enough air pressure to propel the paintball and blow the bolt back. The only thing I do not have figured out is an extractor mechanism to remove a spent shell. Blowback or not it's something I have to work on. Since this particular cannon is not magezine fed there really is no reason for it in this build. A future cannon simular to this will use that most likely. I designed it with the basic concepts of inertia as a proof of concept. The blowback action for now is just a secondary feature.

The cartridge is similar to the bolt assembly. Since the type of CPVC I used fits perfectly inside the next size up, it made sense to make them from 1 1/2" pieces of scrap pipe. The video I provided shows this in more detail.

Just like the two cannons before this one, I reused the sampling cylinder to come up with this creation. It can handle pressures up to 1000 PSI so I should be fine with 145 PSI. In addition to the pressure gauge i have a regulator on it. I can use this to slowly bleed off the pressure without firing the cannon.

Here are the specs:

Barrel/Bore (.695"ID Approx.) X 42"L 3/4 CPVC
PB Projectile 3 Grams .690"D + or -
135-145 Psi/9.6-9.9 BAR
Approx. 767-800 Ft/s
67.9 Ft*lbs Kinetic Energy

Now taking the fact that the bolt does not fit completely snug inside the 1" CPVC, some air does get past but only a little. The paintball is not going to use all of the air to achieve the velocity that it does. A chronograph test indicated an average of 795-797 fps at 145 PSI. Much like a semi-auto, the projectile will have already cleared the muzzle before the bolt has even reached the end of its travel.

I have provided some pictures and a video. More damage pics to follow.


[youtube]http://www.youtube.com/watch?v=R-aMpGeLZt4[/youtube][/code]
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Attachments
SPECS.JPG
GGDT specs
Full.JPG
With barrel
Take down.JPG
Taken down
Bolt Assembly.JPG
Shows how the bolt operates
Tank.JPG
Closeup of the tank section
DSCF1455.JPG
Closeup of bolt
DSCF1467.JPG
Damage from PB @ 145 psi from 20 feet
DSCF1469.JPG
Exit
DSCF1484.JPG
Looking through the breech section, you can see the port, youll notice that the tube is one continuous piece
DSCF1488.JPG
This how the bolt, cartridge, and breech line up in relation to the air port in the T fitting.
DSCF1491.JPG
Closeup of the bolt. The end is cut in such away that will allow air to enter from behind the cartridge.
Last edited by Tetsuo315 on Mon Apr 12, 2010 4:18 pm, edited 4 times in total.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 11, 2010 1:54 pm

Very slick, as to cartridge ejection you might want to have a look at this ;)
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Unread postAuthor: Gun Freak » Sun Apr 11, 2010 4:02 pm

How does the bolt push the cart far enough into the barrel for it to be in front of the air? Also how do you get the carts out? Nice gun, I like the idea of cartridges.
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Unread postAuthor: Tetsuo315 » Sun Apr 11, 2010 11:06 pm

Thanks for the link Jacks, that will help :)

How does the bolt push the cart far enough into the barrel for it to be in front of the air? Also how do you get the carts out? Nice gun, I like the idea of cartridges.


The spring provides enough recoil to force the bolt and cartridge against the breech. The bolt is also cut in such away to allow air to pass by. See the new pics above. As for removing the carts, I have to stand the cannon up and let it slide out. This is until I come up with a way to extract them with the bolt

Thanks for the comments
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Unread postAuthor: Patto » Mon Apr 12, 2010 5:34 am

man this really is a beautiful cannon !! blow back to impress :D

have you tried it with out shells with a hopper set up ?
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Unread postAuthor: Crna Legija » Mon Apr 12, 2010 6:17 am

very nice,you could maybe use a magnet on the bolt to pull out the spent casing
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Unread postAuthor: Tetsuo315 » Mon Apr 12, 2010 10:36 am

-_- wrote:very nice,you could maybe use a magnet on the bolt to pull out the spent casing


Funny you mention that. I was just considering using ring magnets on the casings and a smaller one on the bolt

Patto wrote:have you tried it without shells with a hopper set up ?


No, but with the current setup, the paintball would fall down the air port. I would have to alter the breech so that it tapers down, and make a different bolt to catch the paintball...the gears are turning.

Thanks
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Last edited by Tetsuo315 on Mon Apr 12, 2010 3:59 pm, edited 2 times in total.
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Unread postAuthor: SEAKING9006 » Mon Apr 12, 2010 11:14 am

Check out boltsniper's work on cartridge fed nerf rifles, the FAR and the SCAR-N in particular. Just google boltsniper.

Or, wait a few hours until I get home so I can show you mine. It takes about two hours of fabrication to get a working bolt face. I use a brass ejector pin and a bent staple as an extractor. Weather you use rimmed or rimless cartridges is up to you. I use rimless, and the groove is slightly challenging to do properly. And I used Sch40 instead of CPVC.
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Unread postAuthor: al-xg » Mon Apr 12, 2010 4:41 pm

Very nice. I have used a cartridge extractor using friction (like Iknowmy3table's Deus Ex Machina but made from copper) with a pump action grip and it proved to be reliable so could be another option for your build. the hardest bit will be the feeding rather than the extraction in my opinion.

Ah and to stop the paintballs rolling down, you could just leave a strip of pipe (or something thin added after) longways across the hole, basically two holes but shaped as one providing a small " bridge" for the projectile. Doesn't limit the flow too much and is resistant to the high pressure hammering.
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Last edited by al-xg on Tue Apr 13, 2010 3:57 pm, edited 1 time in total.
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Unread postAuthor: spudtyrrant » Mon Apr 12, 2010 7:27 pm

honestly the thing that most interest me is that sampling cylinder, seems like a good hybrid chamber :) , but the stuff you attached to it is nice too :D
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Unread postAuthor: Tetsuo315 » Tue Apr 13, 2010 5:25 pm

I absolutely love this forum site. You guys are great.

al-xg wrote:Ah and to stop the paintballs rolling down, you could just leave a strip of pipe (or something thin added after) longways across the hole, basically two holes but shaped as one providing a small " bridge" for the projectile. Doesn't limit the flow too much and is resistant to the high pressure hammering.


That would be the best solution for this type of project for now.
The extraction method used by boltsniper seems to be the way to extract/eject spent shells. His builds look so clean. If I want to get something going with this cannon, the friction method would also be nice for extracting.
The recoil spring would be removed to use it as a bolt action cannon.
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Unread postAuthor: Lockednloaded » Sat Jun 19, 2010 12:25 am

I hate to kick this up, only a few months anyway, but have you had any luck with cartridge ejection? any mag construction? it looks like it has huge potential
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Unread postAuthor: woodscout » Fri Jun 25, 2010 3:30 pm

good looking gun + good power + good action = hell of a lot of fun :D this gives me thousands of ideas, i need to start drawing :)

very good work! i think this is the most beautifull pvc gun in here
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