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Air rifling...

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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Air rifling...

Unread postAuthor: jackssmirkingrevenge » Thu Nov 06, 2008 4:06 pm

... doesn't work :roll:

[youtube]http://www.youtube.com/watch?v=uNIL0bChyPk&feature=related[/youtube]
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Unread postAuthor: ALIHISGREAT » Thu Nov 06, 2008 4:10 pm

How do Nerf vortexes spin in flight then? :wink:
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 06, 2008 4:17 pm

ALIHISGREAT wrote:How do Nerf vortexes spin in flight then? :wink:


Canted fins, ya cheeky cant :p
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Unread postAuthor: ALIHISGREAT » Thu Nov 06, 2008 4:23 pm

jackssmirkingrevenge wrote:
ALIHISGREAT wrote:How do Nerf vortexes spin in flight then? :wink:


Canted fins, ya cheeky cant :p


well its almost the same :D

instead of a slug, i would shoot a fin stabilized grenade out of a shotgun as shown in this video http://uk.youtube.com/watch?v=p4ebtj1jR7c

much better than 'air rifling'
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 06, 2008 4:46 pm

Ah, the FRAG-12... practically equivalent to a 20mm cannon shell, albeit at a much lower velocity.

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Unread postAuthor: ALIHISGREAT » Thu Nov 06, 2008 4:54 pm

jackssmirkingrevenge wrote:Ah, the FRAG-12... practically equivalent to a 20mm cannon shell, albeit at a much lower velocity.

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if only i could make fin stabilized ammo for my spudguns, it would certainly make accuracy less of a problem..

anyway, back to the air rifling, maybe if the slug was not sealed inthe barrel, so the 'rifling' would extend the whole way back on the slug to allow the slug to turn? because as it is, he air doesn't flow the whole way back in the 'rifling'
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 06, 2008 5:17 pm

ALIHISGREAT wrote:anyway, back to the air rifling, maybe if the slug was not sealed inthe barrel, so the 'rifling' would extend the whole way back on the slug to allow the slug to turn? because as it is, he air doesn't flow the whole way back in the 'rifling'


You mean like this finned slug?

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Re: Air rifling...

Unread postAuthor: Ragnarok » Thu Nov 06, 2008 5:27 pm

jackssmirkingrevenge wrote:... doesn't work

I beg to differ, it works fine here
:D

That aside, I will be attempting, if I find the time for it, experimentation with drag induced spin, provided by angled leading fin edges. I believe that in the process, I can also drastically reduce the drag from the fins in this manner - and at the same time, cut several accuracy problems that can arise from darts.
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Does that thing kinda look like a big cat to you?
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Unread postAuthor: jimmy101 » Thu Nov 06, 2008 5:29 pm

I don't think that video really says anything about the effectiveness of rifling on an air rifle. It appears that the images are within an inch or so of the muzzle. If the barrel is poorly crowned it'll kick the round off center as shown in the video.

To say anything difinitive based on video you would need images of the round at several distances from the barrel, not just at the first inch or so. Heck, that round shown may well have stabilized after a foot or so.
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Unread postAuthor: ALIHISGREAT » Thu Nov 06, 2008 5:30 pm

yeah exactly like that (only i was thinking of shallower grooves), surely that works?

although, its really using fins not 'rifling'....
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Unread postAuthor: Ragnarok » Thu Nov 06, 2008 5:35 pm

jimmy101 wrote:I don't think that video really says anything about the effectiveness of rifling on an air rifle.

No, not rifling on an air rifle (even if I deliberately misinterpreted it) - spin induced through the drag from air passing over grooves made in a projectile fired from a smoothbore.
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 06, 2008 5:41 pm

jimmy101 wrote:I don't think that video really says anything about the effectiveness of rifling on an air rifle. It appears that the images are within an inch or so of the muzzle. If the barrel is poorly crowned it'll kick the round off center as shown in the video.


Not an air rifle but a Brenneke slug fired from a 12 bore shotgun:

Image

Fired from a smoothbore barrel, the grooves cut into the lead component are usually thought to spin the round for stability, when in fact this has no real effect. The slug travels head first by virtue of its forward centre of gravity thanks to the fibre wad as its base

Rag, I should have seen that coming *facepalm* :P :D
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Unread postAuthor: SEAKING9006 » Thu Nov 06, 2008 6:22 pm

I that grenade just gave me an idea for making a folding-fin projectile out of PVC!! All you need to do is cut a short piece of PVC pipe into four sections, use four small leaf-springs by cutting a slot into the main shell and epoxying one side of the spring into it, and epoxy the other to the fin. Sand away the inside of the fins until they fit flush.
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Unread postAuthor: mark.f » Thu Nov 06, 2008 6:37 pm

It's not actually intended to be rifling. They're basically just drag-inducing fins to keep the projectile from tumbling uncontrollably.
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Unread postAuthor: FishBoy » Thu Nov 06, 2008 9:02 pm

markfh11q wrote:It's not actually intended to be rifling. They're basically just drag-inducing fins to keep the projectile from tumbling uncontrollably.


But if you were to grind down the leading edges of the fins, that idea could have some potential (beastliness). Even though it's somewhat impratical as anything more than an experimental round, due to the fact that it's pretty labor intensive for something you want a lot of, & will inevitably be destroyed.
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