Good sized Advanced Cannon Build, Plus ammo Idea

[Rob748]

Hi everyone, I had a little build I have been running off Hgdt for a few months, Havent had the money to get around to build it, Its Advanced, And Im hoping to push a 1 ounce projectile close to 900fps.

4 inch X 22 inch Schedule 40 PVC. A 2inch X 90inch barrel pvc barrel
Metered MAPP gas system, 4 inch Dual Mixing Chamber Fans.
8 multiple spark gap
Taser ignition
Burst Disk Valves
Rifled 2 inch Barrel.
18 volt battery setup
And I had a little Idea for a long distance round 100 yards plus. It would take some kind of light metal alloy, Shaped like a rifle bullet, but hollow. Kind of like a pellet, a very large pellet Id like to keep it at a ounce in weight or lower. Id have metal machined, prolly measuered out to 1.96in. plus the rifled barrel, I could see it having some kind of significant accuracy for such a large slow moving bullet.

For the combustion chamber Id have the Pvc ball valve in the rear for easier venting, screwed on to the threaded pvc connectors,. Then split it near the middle, with another threaded connection. Im trying this for easier cannon repair, or improvements. In the middle connection Id have a fan placed inside of it, and a fan at the rear running off 18 volts each. And A spark strip that made like starmans Triple thunder design. A union, with 65psi Burst Disks. On Hgdt I get a Ounce traveling close to 1050fps, Im amssuming its not dead on so Im rounding to 900-925fps. The dual Fan setup is for more turblence, and wicked fast venting. Both run off toggle switches for optional fans.
I have 250 dollars to create this gun which I figure is way enough maybe even for machine work.

Any thoughts or Ideas on Improvements ?

[qwerty]

900fps seems a bit much but other than that it all looks well thought out.

[psycix]

Don't place any fans near the barrel opening. The insane flow will break it.
One in back and one in mid.
Make em both blow in the same direction so that you can use them for venting.
A possibly better way to mix with two fans would be with small fans (1/2 chamber diameter or smaller) next to each other, blowing in the opposite directions.

Don't forget that rifling will take some off your kinetic energy. How do you plan to rifle the barrel? And make sure that the projectile will have some grip on it.

[SpudBlaster15]

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[Biopyro]

You could account for the length by putting the handle somewhere further down the barrel, so that the chamber extends past your shoulder. You'd probably need something to direct the recoil into your shoulder though.

(I like the angel view of the ammo )

[jimmy101]

8 spark gaps seems a bit overkill. 22" long chamber of 4" D pipe ... five or six spark gaps should be more than enough.

Two fans really are not needed and it is unlikely that the forward one will last very long. Since this is a burst disk gun, the somewhat faster burn from the second fan really isn't needed.

Since this is a burst disk gun a lot of the buzzes and whistles aren't needed and won't actually increase the gun's performance. Propane vs MAPP won't make much difference in a burst disk gun. Multiple spark gaps won't make much difference. Multiple fans won't make much difference.

The burst disk and ammo is what controls how this gun performs.

(Edit: 22" long barrel should say chamber.)