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Unread postPosted: Sun Jul 22, 2007 8:00 am
Author: VH_man
hahaha. 1300 FPS is above the sound barrier at sea level

1128 FPS is the sound barrier..... so i gues we have a supersonic pneumatic......

anyway, 1300 FPS is fast enough to make the BB fly across my yard and hit my target before the muzzle sound goes away.

build this, and make me happy, becasue im not allowed to make BB guns...... i dont know why as my marble canon is 10000X mored dangerous.

Unread postPosted: Sun Jul 22, 2007 8:03 am
Author: CpTn_lAw
No it wasn't! i was a single shot high power coaxial rifle...barrel was 60 cm of 8mm OD copper, best speed achieved with 0.12grams BB. It went straight about 5 to 10 meters, but it had lost about half of it's energy at that point. A bb would blast against a wall...i found bits of flashy yellow BB in a cardboard box with 6mm plywood inside. The BB went completely through, but was desintegrated.
It had way much power with 0.2 gram bb's. they would go straight about 20 meters, and then fly up verticaly.
You need to consider that for small caliber weapons, you need much more pressure to push a projectile proportionnaly heavy than in a big bore canon.
surface is smaller, an thus providing less contact to apply the force. (wow if someone can understand me here......my english when talking about physics is very poor...i could explain it in french)
So, basicly, at close ranges, it is devastating, at long range, i advise you choose 0.88 steel BB's.


Your marble canon compells you to pay a lot of attention to where you shoot. A marble will blast into piece against a hard wall, whereas with a BB rifle, you're not dealing with the same power, but neither are you dealing with the same velocity. A BB can bounce off and still penetrate your skin.
I did a penetrative test, a BB would go through my gelatine block, straight through, whereas a marble would be stuck in. difference is, with the BB the gel. block wouldn't even move, but with the marble it would fly back 3' .

Unread postPosted: Sun Jul 22, 2007 8:15 am
Author: al-xg
There is that theory on dead space though, and that condor airgun does seem to be a precharged one (read it once more: ahh damn you posted that link... :roll: )

I did once try to make a chronograph using the same idea as jimmy's, but i only had photoresitors.
I tested it and it seemed to work until i realied that the readings i was getting when turning of the light had nothing to do with light at all, but probably more with some electromagetic field generated by the lamp... :?
I'll try again if i comme across some phototransistors or photodiodes.

Unread postPosted: Sun Jul 22, 2007 8:23 am
Author: VH_man
ummm, marbles dont shatter for me when they hit a rock............ they chip, but they DEFINETLY come back at you........ and it hurts, alot...........

Unread postPosted: Sun Jul 22, 2007 8:25 am
Author: CpTn_lAw
They would bounce off when i used only 100 psi...i assure you that at 300 psi, they shatter. makes fine glass powder.

Unread postPosted: Sun Jul 22, 2007 8:30 am
Author: Mitchza89
Ah wow... So much information to absorb hahaha. Do you have a link for your copper coax Law? I was considering a Coax over a T valve by a long shot but I've never soldered before. Thats why I've decided to go with the T valve. It will all screw together.

Here is a rough diagram I made on photoshop that will give ya's a rough idea on how it will look. I just stuck the blowgun there for the hell of it but Choas suggested that I use a 1/4 ball valve trigger like what Jack uses on his. Damn good idea concidering I love the whole "pop off valve trigger feel.

Any feedback on the design would be more then appreciated.

Unread postPosted: Sun Jul 22, 2007 9:47 am
Author: spudthug
why not make one like this?

http://www.spudfiles.com/forums/bb-snip ... t9584.html

or this if you want a screw together coax?

http://www.spudfiles.com/forums/spudthu ... t9625.html

Unread postPosted: Sun Jul 22, 2007 10:48 am
Author: VH_man
Thats a nice cannon there. only thing I would change is that i would make a simpler stock.

instead of using the pipe and then the elbow, go to a larger diameter through a reducer fitting and then screw and encap onto the back of it. it uses larger, heavier pipe but its much more comforatable.

if youre still gonna use the elbow, point it downward. it would stink to have the gun uncomforatable to hold because your face has to rest on a giant peice of steel pipe.

Unread postPosted: Sun Jul 22, 2007 10:51 am
Author: spud yeti
The picture looks good, but how are you going to attach the blowgun at that angle?

EDIT: just noticed you using a ball valve, sorry.

Unread postPosted: Sun Jul 22, 2007 12:28 pm
Author: CpTn_lAw

Unread postPosted: Mon Jul 23, 2007 1:04 am
Author: Mitchza89
Holy hell Law, thats gorgeous. You have inspired me. I've just come up with an idea of a Coax and uses a T valve. I'll draw it up right now. This thing is gonna look so damn good.

Unread postPosted: Mon Jul 23, 2007 1:54 am
Author: jackssmirkingrevenge
Law, you cannot claim a velocity of 1,300 fps based solely on GGDT data, particularly given the program's difficulties with dealing with supersonic velocities. Some actual chrono data would be nice ;)

Unread postPosted: Mon Jul 23, 2007 2:28 am
Author: Mitchza89
Ok guys this is the idea i was talking about. Gotta love thinking of something cool on the spot :D I've never seen anything like this. I can't wait to make it and make history hehe.

The nipple between the eblow and the larger tee will be filled with epoxy to reduce the pilot by a hell of a lot as apossed to capping the end of the pipe off the elbow.

The piston will be made out of epoxy more then likely and will sit in the beginning of the chamber. The epoxy plug will act like a wall so I can add a spring behind the piston.

Everything else on it should be pretty self explanitory to the people who know the principles behind Piston Cannons. Any questions, please give me a buzz.

Unread postPosted: Mon Jul 23, 2007 3:08 am
Author: chaos
@ jack, i think law actually did crony the thing. not totaly sure on it but i think he did

Unread postPosted: Mon Jul 23, 2007 8:27 am
Author: jackssmirkingrevenge
chaos wrote:@ jack, i think law actually did crony the thing. not totaly sure on it but i think he did


No mention of a chrony in the thread, I remain skeptical.

Mitchza89 wrote:I just stuck the blowgun there for the hell of it but Choas suggested that I use a 1/4 ball valve trigger like what Jack uses on his.


Actually I use a schrader to trigger my 6mm piston pneumatics - I can afford to because the piston is only 1/2" in diameter and moves back less than 1/8", so the pilot volume is approximately that of a very small insect's left bollock ;)