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Unread postAuthor: judgment_arms » Tue Jan 09, 2007 7:32 pm

Yes, but it’ll involve a little bit of research, I need to now the rate of twist required to stabilize a paintball at 300fps… I tried the green hill formula but, then after spending about an hour figuring it out I found out that it only works on lead or lead core bullets… you seem to know quite a lot about math perhaps you’ll be able to figure this out…
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Unread postAuthor: shadowghost21 » Tue Jan 09, 2007 7:38 pm

Well any sort of spin will help stabalize it in air. TO do everything from scratch (With out a forumla) I would have to derive a new formula and that might take some time. How are you putting spin on your paintball? If you tell me the FPS and (and how many revolutions it will do in the barrel the barrel length I might be able to tell you the velocity that it will spin in air.

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Unread postAuthor: judgment_arms » Tue Jan 09, 2007 7:41 pm

Well, I plan on making a rifling machine…just a sec let me find the link to my paintball rifle, that should explain a bit.

Edit:
Here’s the link: paintball RIFLE
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Unread postAuthor: shadowghost21 » Tue Jan 09, 2007 7:52 pm

I was reading another forum about long barrel and accuarcy and green hill forumula take a look at it.

http://www.nnypaintball.com/viewtopic.p ... 21d1a88af6

EDIT: I wouldn't bother rifling the barrel, unless its a really low spin like 3 or 4 revolutions per inch. Just use a longer smooth bore barrel that is really close the the Diamater of a paintball.
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Unread postAuthor: judgment_arms » Tue Jan 09, 2007 8:16 pm

one guy in link wrote: I wouldn't think rifled barrels would be as accurate. From everything I've seen and read putting spin, even a uniform spin, on a paintball is bad because it wobbles in flight. Shooting a paintball is like shooting a waterbaloon full of Jello. It deforms in flight, if it spins due to its elastic property of its shell and its sweet liquid filling would be off-center due to friction on the sides of the paintball.
The only theory I could think of, where this might work, is picturing the paintball and its components like a gyroscope. As the balls sit in the hopper waiting to be shot the goo is dictated by gravity and settles to the bottom, when fired it all moves to the back of the ball, if you could spin the shell alone with the paint-like-nectar in a static state as the shell revolves around it you could have a good flight.
In a perfect world this would hold true, but then again we on earth have to deal with friction which would drag the paint on the inner lining of the shell making it lopsided in its spin.
Plus the whole while the paintball would be more of an oblong elipse because of acceleration due to firing. The paintball is accelerated from a static state (0fps) to 300fps in about a millisecond! With a shell that is meant to break on impact I'm thinking the paint would be in the back of the shell (due to a heavier density) while the whole shell enlongates until it reaches its terminal velocity. Then the shell would contract to conform back to its natural shape (circular) and then impact. If all environmental factors are ignored, ie wind currents, relative humidity, precipitation, all components of the paintball would be moving at 300fps and would be in accord. At this speed the greatest potential for precise flight is possible. Until that rotten gravity gets a hold of it and A)Sends it to earth B)Hits something other than the target C) Hits Scott or if your lucky D) Hits the target. This kind of stuff never ceaces to amaze me.


This guy made a good argument, but the thing is my barrel is 36inches, by the time it leaves the barrel every thing should be stabilized, the only thing would be if the improvement would be visible in the 18inch test barrel. But with the full sized rifle I think by the time it leaves the barrel, due in part to a slower acceleration, the paint should be pretty well balanced out, seeing how it’s bean spinning for 36inches…but then again you’re the math genius not me, what do you think?

I type to slow,
But anyway, rifling rate of twist is going to be somewhere between 1 in 41, and 1 102 inches. So not even a complete revolution.
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Unread postAuthor: shadowghost21 » Tue Jan 09, 2007 8:20 pm

I think it will be okay, the only real way to find out is to test. Thats how I do everything. Build First, thoery later, after you shot somthing hehehe.


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Unread postAuthor: judgment_arms » Tue Jan 09, 2007 8:30 pm

Figures,
Thanks, I’ve got a lot of work to do, rifling machine’s going to be complicated to make, do in part to lack of specialized tools.
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