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1/4 Brakeline Barrel and Copper Pellet gun

Posted: Fri Mar 05, 2010 9:04 pm
by clemsonguy1125
I just bought a piece of 1/4 brake line as the barrel for my pellet gun. My problem is the 4.5 mm pellet/bb fits loosely and has a gap, will putting wadding behind the pellet yield decent power compared to a perfect sized barrel. Also at a 100psi is it possible to get decent power from a pellet in a piece of 1/2 inch copper pipe as the chamber. It will be a coax. I plan to use a blowgun to pilot it. Ill probably cast a epoxy piston.

Posted: Fri Mar 05, 2010 9:31 pm
by Gun Freak
A .5 in. chamber and a .25 in. barrel on a co ax doesnt leave a big volume unless its really long. Also the wadding will definately help, you just need a ramrod.

Posted: Fri Mar 05, 2010 9:36 pm
by Hubb
Gun Freak wrote:A .5 in. chamber and a .25 in. barrel on a co ax doesnt leave a big volume unless its really long. Also the wadding will definately help, you just need a ramrod.
If you are going with such a small chamber volume, and are doing it in copper pipe, why are you limiting the pressure to only 100psi? GGDT will make a prediction for you, but I can just about bet that you will not be satisfied.

Posted: Fri Mar 05, 2010 9:47 pm
by MrCrowley
From experience, you wont be happy with the power. I wouldn't want to be shot by a BB at 100PSI from such a cannon, but power will seem pretty pathetic. You'll still shoot through a soda can though.

Posted: Fri Mar 05, 2010 9:55 pm
by clemsonguy1125
MrCrowley wrote:From experience, you wont be happy with the power. I wouldn't want to be shot by a BB at 100PSI from such a cannon, but power will seem pretty pathetic. You'll still shoot through a soda can though.
Would a larger chamber volume increase power for a cannon on a coax this size.
And to Hubb
I am limited to 100 psi because I only have a cheap bike pump

Posted: Fri Mar 05, 2010 10:54 pm
by Hubb
A larger chamber will, in fact, increase the power, as long as the barrel is of the right size. As far as your bike pump, consider an upgrade. :wink:

Posted: Fri Mar 05, 2010 11:48 pm
by Crna Legija
make the chamber a bit smaller and get a shock pump, at 300 psi you want be disappointed at the power. make sure if you ram wad and ammo down that you stop it going into the chamber

Posted: Sat Mar 06, 2010 2:43 am
by jackssmirkingrevenge
Hubb wrote:A larger chamber will, in fact, increase the power, as long as the barrel is of the right size. As far as your bike pump, consider an upgrade. :wink:
Couldn't agree more, the smaller you go with calibre the more you need to up the pressure to keep the power up. Remember that to have the same power potential as a 1/2" barrel at 100 psi, a 1/4" barrel needs 400 psi.

A shock pump is a cheap and useful source of 300-400 psi for a small chamber, and if you have access to proper epoxy making a small piston cannon should be no problem at all. You could very easily take this design and make it longer.

Posted: Sat Mar 06, 2010 2:46 pm
by clemsonguy1125
jackssmirkingrevenge wrote:
Hubb wrote:A larger chamber will, in fact, increase the power, as long as the barrel is of the right size. As far as your bike pump, consider an upgrade. :wink:
Couldn't agree more, the smaller you go with calibre the more you need to up the pressure to keep the power up. Remember that to have the same power potential as a 1/2" barrel at 100 psi, a 1/4" barrel needs 400 psi.

A shock pump is a cheap and useful source of 300-400 psi for a small chamber, and if you have access to proper epoxy making a small piston cannon should be no problem at all. You could very easily take this design and make it longer.

I might see about upgrading to a shock pump and I my switch to a 1 inch chamber and a tee valve http://www.spudfiles.com/forums/high-pr ... 19694.html like this, because I dont want to deal with copper and I can screw all these parts together