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25mm Breech Loaded Copper Cannon

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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25mm Breech Loaded Copper Cannon

Unread postAuthor: SubsonicSpud » Wed Mar 04, 2009 5:35 am

G'day Everybody

Well i have finally gotten around to posting up one of my cannons. It is the second copper gun I have made, the first being a half sized prototype. It is not completed yet but is fully operational. Here are the specs.


Caliber 25.4mm (1")
Barrel Length 1520mm (5')

Breech: Bolt Action Sliding barrel type

Chamber Diameter 31.8mm (1 1/4")
Chamber Length 750mm (2.5')

Operating Pressure: 25Bar 360psi (27bar 420psi MAX SWP)

Muzzle velocity 560fps on crony with steel round approx 30grams.

Valve type: fully servicable Barrel sealing piston, "O" ring sealed pilot side. piston vent is 2mm in diameter, and will eventually incorporate a check valve

Valve Material: Acetal with insertion rubber sealing face

Pilot Valve: valve and body from die grinder used for trigger and grip. same style valve as a blow gun, but with a much better flow rate.

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Breech in open position
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Exploded view of valve
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Pilot Assembly
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Refill Station
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The refill tank is an old 9kg Co2 fire extinguisher with a helium tank baloon filling regulator. I have shimmed the spring in the regulator so it maintains a regulated pressure of 25Bar (360psi) will mod it further so it can be adjusted easily

Cannon and Refill Tank
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Damage to 20mm Structural Ply
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Aircon Unit Damage
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Hole through Aircon unit. The round went through the condenser coil, fan, two layers of 1mm sheet steel, 30mm of polystyrene insulation and ended up embedded in the ground :shock: :twisted:
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Still have a few more mods to do like installing a check valve in the piston vent and making a stock and sight.

There will also be MOAR damage pics in the next few days :twisted:


**UPDATE**

Well this afternoon I reworked the piston design a little.The rubber sealing face needed a little more support due to a few seal blow outs,resulting in a few surprise firings :shock: I machined a new washer for the seal and also gave it a conical shape to aid airflow.

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Well the results were rather unexpected, a gain of about 130 fps :twisted:

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Cheers

SubsonicSpud
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Last edited by SubsonicSpud on Thu Mar 05, 2009 8:54 pm, edited 2 times in total.
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Unread postAuthor: Mitchza89 » Wed Mar 04, 2009 5:58 am

I absolutely love it mate. It's about as clean as you can get ;). Great build, I hope to see more damage pic's soon!

All the best,

Mitch.
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Unread postAuthor: rna_duelers » Thu Mar 05, 2009 2:32 am

Agreed,good build and with damage pics like that no one can say it doesnt kick!Get as many damage pics up as you can.I love copper guns,I've only built one and I would love to build another but with a QEV.
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Unread postAuthor: SubsonicSpud » Thu Mar 05, 2009 5:20 am

Thanks for the comments guys.

I have updated my first post with some piston mods i did increasing the muzzle velocity by 140 fps, unfortunately no more damage pics as i did not hit the target

By the way here is some of the ammo i have been shooting
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The steel slug is 12mm in diameter and 30mm long. the rear of the slug is drilled out so it is aerodynamically stable. They are placed in a light wooden discarding sabot to seal in the barrel. The weigh of the slug is 15 grams giving a muzzle energy of about 248 ft*lb. at 695 fps.

Cheers
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Unread postAuthor: rna_duelers » Thu Mar 05, 2009 9:01 pm

140fps increase for only a simple new piston design,thats a great increase for little work.At nearly 700fps with a 15gram slug,wow I got to say you could take down a roo hypotheticaly with that.

Do you have any sheet metal lying around to shoot at?I always love to see how rounds react on impact.
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Unread postAuthor: SubsonicSpud » Thu Mar 05, 2009 9:37 pm

yep it was a pretty big increase for such a small mod, I cant think of any other variables that could have changed the fps. I think i can get a bit more out of the ammo yet, the wooden sabots weigh about 4 to 5 grams so they take a quarter of the total energy to accelerate. I'll see what i can do to get them down to half that. I'll see what expendible objects I have lying around, i might try a railway sleeper. Some terracotta pots might be interesting too :twisted:

SubsonicSpud
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Unread postAuthor: daniel323 » Thu Mar 05, 2009 10:29 pm

Great cannon.
How many shots do you get out of the CO2 Tank at 360 psi?
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Unread postAuthor: psycix » Fri Mar 06, 2009 3:42 pm

Very well built cannon!
I just cant think of any criticism or improvement. :D
I love it!


EDIT:
Oh I thought of one:
Add a QEV as pilot valve to further enhance performance.
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Till the day I'm dieing, I'll keep them spuddies flying, 'cause I can!

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Unread postAuthor: SubsonicSpud » Sat Mar 07, 2009 2:47 am

daniel323 wrote:Great cannon.
How many shots do you get out of the CO2 Tank at 360 psi?


I have not actually counted how many fills I get out of the tank yet. I roughly worked it out to be about 7-8 . The aircon compressor only pumps up to 600psi. I might try a fridge compressor to get a bit more pressure into it, considering the tank and regulator can take up to 3000psi.
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