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Projectile specific gravity

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: Crna Legija » Mon Oct 18, 2010 6:31 am

come on you live in croatia im sure you could find a old ak-47 from the war and use the barrel :D
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Unread postAuthor: Ragnarok » Mon Oct 18, 2010 9:37 am

FighterAce wrote:Thats quite a feat of engineering and aerodynamics... I didn't graduate either so how could I make something like that?

The designs don't need to be complex. It's more about making the projectiles with a reasonable degree of consistency (and a decent fit in the barrel).

I've seen things as simple as nail darts (made with a little care) group very well.

About the rifling angle formula... whos right? Ragnarok or al-xg or both?

al-xg's formula treats the rifling as a zig-zag along the barrel. Mine treats it as a spiral around the barrel.

The latter is... more appropriate, I think.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: SpudFarm » Mon Oct 18, 2010 12:00 pm

Well, I don't understand why you have to make it harder then it is. For a homemade gun it isn't really THAT important to have perfect rifling.

I prefer Dart/penetrator style projectiles before rifle like projectiles. They are not hard to make at all, the projectile in the picture was made with stuff found in a garbage can.. I also had a hurry when making this.

Image
Might not be the best example as I didn't even think about good aerodynamics when making it, It was only made to penetrate (And that it did :D)

Try to have a pm conversation with Ragnarok on the matter of dart like projectiles, you'll be impressed! He will tell you a million things you don't understand, but it can be found on the internet and you never forget it again.

THAT was my five pesetas.
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"Made in France"
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Unread postAuthor: FighterAce » Mon Oct 18, 2010 1:27 pm

Thanks Ragnarok!

I already use nail darts and I'm getting groups less then 5cm in diameter at 10-15 meters but I want to go further. Thats why I'm trying to use spin stabilized projectiles. And I didnt say I'm gonna make perfect rifling. I'm just trying to get the general idea how it should be. If I know its gotta be lets say 15° I'm gonna try to make it as close to 15°. If I dont know what its got to be then whats the point?

I also prefer darts (for now) but I want something more.. something more accurate at longer range...
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Unread postAuthor: al-xg » Mon Oct 18, 2010 6:03 pm

My rifled barrels have had rifling angles between 2-4°, I mostly 4° though. (that is the angle on the cutting tool, so this is regardless of the formula used)

I use my pneumatic spudguns, like big bore air rifles, so the rifled barrel is just quite practical. I cast 15-20 bullets, shoot them, then melt them back down. But the barrel will also stabilise potato, and you can still shoot darts, or shot (although I do suspect the shot partern is quite a bit larger when rifling is used...).

Optimum accurate gyroscopic stabilisation might require accurate rifling, but just stopping a projectile from tumbling doesn't seem to require too much fuss.

Basic but effective rifling really isn't that hard to achieve.
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Unread postAuthor: jackssmirkingrevenge » Tue Oct 19, 2010 12:31 am

al-xg wrote:(although I do suspect the shot partern is quite a bit larger when rifling is used...)


Donuts yo!

:roll: :D
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Unread postAuthor: FighterAce » Wed Oct 20, 2010 5:35 pm

I decided to go with lead... its easier to work with it then I thought :D

Since the gun is sure to be front heavy with a copper bolt and copper barrel I'm gonna use aluminum for bolt and copper barrel with 8mm ID.

Would copper tubing with 1mm wall thickness be ok to rifle? Would tool steel be a good choice to make the rifling tool from?
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Unread postAuthor: Crna Legija » Wed Oct 20, 2010 7:35 pm

The copper would probbly were out quickly if you use lead as ammo.
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