SpudFiles

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.




Breech in open position


Exploded view of valve


Pilot Assembly


Refill Station


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


Damage to 20mm Structural Ply


Aircon Unit Damage


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


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


**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 I machined a new washer for the seal and also gave it a conical shape to aid airflow.



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




Cheers

SubsonicSpud

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.

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.

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


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

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.

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

SubsonicSpud

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

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


EDIT:
Oh I thought of one:
Add a QEV as pilot valve to further enhance performance.

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.