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6mm coaxial

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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6mm coaxial

Unread postAuthor: hyldgaard » Mon Mar 31, 2008 11:13 am

Hello.
Im about to start my new project which is a 6mm coaxial. I know the power wont be really impressive, its just to introduce myself to coaxials, as i have never build one before.
My plan is 100cm of ½" galvanized pipe chamber with a 140cm 8mm copper pipe barrel. I will probably be running it at around 20bar, maybe more. My main ammo would be .89g steel bb's.
My question is, what velocity would i be looking at with a 0.12g bb? GGDT predicts 568m/s which i consider a bit next to reality. 012g bb's are a cheap alternative to the steel ones, so i was just wondering if they were at all useable as ammo.
Thanks in advance
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Unread postAuthor: ALIHISGREAT » Mon Mar 31, 2008 11:26 am

you should be getting 800-1000 fps as a guess because anything more is unrealistic as it is approaching the speed of sound :twisted:

Alasdair.
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Unread postAuthor: Brian the brain » Mon Mar 31, 2008 11:28 am

I think you might be wrong about the power.That will easily outdo the average off the shelf airgun.

GGDT won't be too far off, maybe the estimate is even a little low...
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Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: bigbob12345 » Mon Mar 31, 2008 11:35 am

with that much chamber Id say 1000fps-1100fps, just a little below the sound barrier.
if you uped the pressure to say 500psi, then you actually may break the sound barrier
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Unread postAuthor: ALIHISGREAT » Mon Mar 31, 2008 11:37 am

^^^ he would need to heat the air.....
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Unread postAuthor: bigbob12345 » Mon Mar 31, 2008 11:39 am

I disagree
as long as it was at a moderatly high temp(70degrees F and above)I think he would have a fairly good chance at it
of course it will ba a lot hader to do with a piston valve than a burst disk but Id say its possible.
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Unread postAuthor: ALIHISGREAT » Mon Mar 31, 2008 11:46 am

hmm whats 70 degrees in celcius... (i'm a brit)..... ahhh 21 degrees C..... thats not that hot, and the fact that the speed of sound increases with temperature.....

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Unread postAuthor: POLAND_SPUD » Mon Mar 31, 2008 12:17 pm

lol I thought that 70 degrees C is 70 degrees C.... :wink:

I hope one day world would use one set of (metric :D ) units
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Unread postAuthor: hyldgaard » Mon Mar 31, 2008 12:18 pm

To be honest im not that known in the area of supersonic spudding, but it could be funny to make a supersonic gun. I know that supersonic is possible with compressed air(commercially available guns) but i also know that noone i have heard of yet has achieved it with a pneumatic spudgun, so its deifnately not easy.
Brianthebrain can you tell me why you think GGDT is underestimating the power? sounds interesting 8)
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Unread postAuthor: Brian the brain » Mon Mar 31, 2008 12:48 pm

Well..that was to emphesise GGDT did not predict "next to reality"

It is more or less correct most of the time as far as I know.

I'm just not sure you entered all the right dimensions.Because my guts tell me you are gonna get about mach 0.8 of the speed of sound.
But what do I know?
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Unread postAuthor: hyldgaard » Mon Mar 31, 2008 2:14 pm

You probably know more than me on this area ;)
i guess that i will just have to try and make this and see how it goes :)
thanks everybody
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 01, 2008 3:56 am

With those specifications you'll be doing high subsonic velocities with lightweight projectiles, but I doubt you'll go supersonic. However with heavier projectiles as to performance I'd expect you'd get in the 15-30 ft/lbs region, it will make a decent sniper rifle ;)
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Unread postAuthor: hyldgaard » Tue Apr 01, 2008 4:54 am

jackssmirkingrevenge wrote:With those specifications you'll be doing high subsonic velocities with lightweight projectiles, but I doubt you'll go supersonic. However with heavier projectiles as to performance I'd expect you'd get in the 15-30 ft/lbs region, it will make a decent sniper rifle ;)

Any ideas on how high pressure would have to be to go supersonic?
And yeah, my idea was to make something a bit more accurate with a little less power than usually, so i think this will suit my needs :) wouldnt exactly call it a sniper rifle, but lets not start that discussion :lol:
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Unread postAuthor: jackssmirkingrevenge » Tue Apr 01, 2008 5:03 am

There's only way to find out, keep pumping ;) with my 6mm burst disk at around 28 bar the best i got was just over 1100 feet per second.

What are you using as a piston and how will it be piloted?

I wouldn't say 0.12 gram BBs are very useful ammo, they do fly fast but lost velocity very quickly, both as they travel in the air and through a target.

Look at the difference in penetration between a 0.25g BB and a 0.12g BB from the burst disk launcher.
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Unread postAuthor: hyldgaard » Tue Apr 01, 2008 5:16 am

jackssmirkingrevenge wrote:There's only way to find out, keep pumping ;) with my 6mm burst disk at around 28 bar the best i got was just over 1100 feet per second.

What are you using as a piston and how will it be piloted?

I wouldn't say 0.12 gram BBs are very useful ammo, they do fly fast but lost velocity very quickly, both as they travel in the air and through a target.

Look at the difference in penetration between a 0.25g BB and a 0.12g BB from the burst disk launcher.

Well, pressure is not a problem as i have a fridge compressor, my concern is how much pressure i dare putting into the gun. i honestly have no clue on how high ½" galvanized fittings are rated.
I have yet to decide on a piston, so im open for suggestions :) my thought on piloting was a 3/8" qev (crossed fingers hoping to get it on ebay) and a blowgun for easy triggering.
I wasnt planning on using 0.12gram bbs as main ammo, just as a cheap alternative. Looking at your "test results" i have great expectations for the 0.89g steel bbs :twisted:
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