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A Question for Warren

 
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Old 09-19-2001, 07:46 AM
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Join Date: May 2001
Location: Arco, ID 83213
Posts: 80
Re: A Question for Warren

Blaine,

A big difficulty in making calculations concerning the muzzle gas flow is the extreme transient nature of the parameters. The gas pressure goes from many thousands of psi to zero in a fraction of a second and the temperature changes over a thousand degress F. in nearly as short a time.

The first shock wave of the gas exhaust occurs at the crown of the muzzle. This is a true supersonic nozzle shock and is reflected back into the center of the stream. With a flat based bullet the reflected shock will encounter the bullet base as it is leaving the muzzle. With a boattail it will encounter the heel, or boattail and be reflected off. As the bullet goes further away from the muzzle there indeed may be a point where the delta V of the gas over the bullet heel may be greater than 1200 fps but in that environment it will take a much great delta V than that to create a shock. Collected data does not support the theory as the recorded noise would have to be different, and it is not.

Again, the gas flow amplifies the initial yaw caused as the bullet transitions from rotating around it's center of form to rotating around it's center of mass. This assumes symmetrical flow initially. Any nonsymmetries in muzzle, crown, or bullet base will add other yaw vectors.

A well designed bullet has yaw damping factors in the negative numbers to reduce the yaw. Any bullet that doesn't will become unstable in short order.

[ 09-19-2001: Message edited by: Warren Jensen ]

[ 09-19-2001: Message edited by: Warren Jensen ]
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