SpudFiles

I have spent the last few weeks building and troubleshooting my new cannon. It is a full metal pneumatic with a 1" tee housing the piston made from a bolt and rubber washers. It has a 1/2" copper barrel and shoots AA batteries and shotgun shot, amongst other things.

Backing up a bit, here's a picture of my old gun. It had a lot of plastic and a 3/4" pvc piston with an o-ring. It worked fine until the gasket on the front blew off. Then,, 2 weeks of troubleshooting messing with washers and lapping sealing faces.



BUT 3 WEEKS LATER I GOT IT FIGURED OUT!!!

Here's a rundown on the new gun

I just got a fridge compressor to fill up the gun,,, I haven't gone above 200psi yet. I need to get a better air hose and build up a little confidence first. I have a free air tank and 600psi gauge on the way (and popoff soon!)



And I added a luxurious switch



And now for the gun!!

I asked around and one of my good friends got me a couple old co2 tanks that were too old to be refilled. We used a torch and some effort to get the regulators off. One simple piece at the hardware store got the 12oz tank on to the gun. (20oz in the future!)

I got these tanks to replace the pvc chamber I had so I can go up in psi.

I drilled out the adapter because it seemed a little restrictive



after:





12oz tank with new fitting on left, 9oz tank with loose reg on right



The new, somewhat pricey, sealing face (2nd time I've soldered pipe)



And the piston



BALL VALVE will be replaced with a CHECK VALVE soon because it is very dangerous.







SOME DAMAGE!!

Stockpile of dead AA batteries



At 100psi and 25 feet the gun can shoot a AA battery though particle board. At 200psi the it shoots clean through the particle board.

(ignore the target, it was painted on after I took most of the shots (at ~100psi))



Shot at wooden board from 10 feet at 160psi



My neighbor gave me some lead shot and 410 wads. I set up a couple pop cans at 20 feet and shot at 200psi





And here's a money shot of me with the original gun, which shot a nerf dart though a beer can at about 60psi.



This is just the beginning,, this is a WIP. More impressive damage pics to come,, and a video is in the works! Some shots are already recorded and I will make more once I get it up closer to,, eh 300-400psi?

And comments/suggestions/warnings/criticism is welcome!!

EDIT: video in this post - http://www.spudfiles.com/forums/viewtop ... tml#322425

Its great! I like it alot and makes me want to get back to fixing up my old cannons, just wish I had the funds.

Great that you made it all metal now, definitely giving your metal fittings some respect there.

Happy Shooting!

Nicely done and especially nicely presented, love the luxurious switch It looks like it will take a lot more than 200 psi, definitely you can take it to 450 psi before the blowgun starts to leak beware the noise though!

Let's see some videos

You might want to consider piloting with the ball valve to go to higher pressures, it will reduce pilot volume too:

Well done. I like it.

looks great, good gun man,

That cannon is... A beast. I love it!! Nice job!!

I got a video up! And some questions..

I was playing with GGDT, and upping the pressure really doesn't up the velocity quite as much as I had hoped.. I get about 425fps at 400psi. I think I am getting about 350fps at 250psi.

What can I do to get my velocity up? Is it all in the valve size?

And if you can see anything horribly wrong with my numbers in GGDT from the video, let me know.

Here's the video

[youtube][/youtube]

Be careful where you aim that thing when you're filling it, you never know when the face will blow or the trigger get tapped so just be careful, nice garage too it looks like mine 8) Looks really fun to shoot and also be careful when you are shooting heavier things cause the high pressure and heavy projectile can make a lot of recoil and it will eat your face if you hold it like that

Battery bounce You guys just might start wearing balistic eyewear after an unfortunate ricochet and a lenghty eye surgery

metallover wrote:I was playing with GGDT, and upping the pressure really doesn't up the velocity quite as much as I had hoped.. I get about 425fps at 400psi. I think I am getting about 350fps at 250psi.

What can I do to get my velocity up? Is it all in the valve size?

If you simply want high velocity, you need a lighter projectile.

Remember, doubling the pressure might double the projectile energy, but this doesn't mean double the velocity.

A 10 gram projectile at 500 feet per second carries 86 foot pounds of energy.

To have double that amount, it only needs to go 210 feet per second faster.

If we double the original velocity to 1000 fps, we get 343 ft/lbs, four times the original muzzle energy - this would mean it needs four times the power to push it along.

Batteries bounce only when launched at slow speeds. At high speeds they go splat. Goggles or safety glasses is highly recommended for flying shrapnel. Most major parts can be found within 10 feet of the impact zone.

Thanks guys! I never thought batteries could be so deadly! I'll be more careful with the shrapnel!

JSR thanks for the explanation. The situation is similar for e-bikes now that I think about it. I'll look around and find some lighter ammo!

Side note 1, I am looking for a .22 barrel. I might take a trip and find an arrow shaft that will work..

side note 2, I ordered the parts to build a DIY chronograph. I'm really exicted about that!

go on ebay fine a long cheap one that has riflings. thats were ive oot mine in the past

Crosman .22 barrels are cheap.

Can be had up to 24" in length.

Gippeto wrote:Crosman .22 barrels are cheap.

Can be had up to 24" in length.

i got that very same barrel off ebay. crosman .22 24 inches. good deals