im working on a sub-caliber wildcat that uses an aero-stable projectile (similar to a fin-stabilized flechette). i have seen reference to a "general rule" that projectiles cannot be gyroscopically stabilized if their l:d ratio exceeds 5:1and therefore they must have fins. the projectile im working with doesnt exceed that rule but it is inherently stable in that its cg is ahead of its cp similar to a flechette. i have also read that even some fin-stabilized projectiles are given a slow spin to increase accuracy (such as the flechette firing steyr acr which had a rifling twist of something like 1:200). so my question is: how does one determine the correct twist for long, skinny fin-stabilized projectiles and for (in my case) short and fat, yet aero-stable projectiles.

dfs,

If you are looking for a simple formula and ACCURATE formula, it does not exist. The calculation you need is a very long and detailed one. I used to do these by hand and they would take me about three days. I have high speed computers do them now.

If you want the BEST program for the calculation it is PRODAS and is written and sold by ARROWTECH of South Burlington, VT. (http://www.prodas.com ). It is not cheap.
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Warren Jensen

Warren@lostriverballistic.com
lostriverballistic.com

[This message has been edited by Warren Jensen (edited 08-03-2001).]

thanks for the info. i think that software is what im looking for. how much did it run you? id like to know exactly how far out of my price range it is before i call and ask about their 45 day trial.

dfs

The basic package starts at $6K. The additional components run about $1500 each.

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Warren Jensen

Warren@lostriverballistic.com
lostriverballistic.com