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Author Topic: Center of Gravity & Center of Pressure  (Read 333 times)

jeff houck

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Center of Gravity & Center of Pressure
« on: January 09, 2019, 08:02:49 PM »
Bullet SC382-238-RF-X1 shows the CofG and CofP as being at the same point. This is a gas check bullet design.
1. Are these two points calculated with the gas chec on or off?
2. Since these two points are at the same location in the bullet will this bullet still show a yaw when fired in a 12" twist barrel?
3. Will this bullet be more stable at subsonic vel. than a bullet with the CofG and the CofP widely seperated?



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Re: Center of Gravity & Center of Pressure
« Reply #1 on: January 14, 2019, 02:55:34 PM »
Calculated with the gas check off
The gas checked bullet should be more stable

With out Gas Check
CG 48.99%
CP 48.99%

With Gas Check
CG 47.59%
CP 47.90%

The best explanation I can offer to visualize CG vs. CP is if you were to balance the bullet on the edge of a knife blade. The actual bullet's balance point would be the CG. Now we cut out a silhouette of the bullet from stiff paper stock and balance it on the knife, that would be CP. So it is a 3D to a 2D relationship.

This drawing is exgagirated for the example

From Long Range Shooting: External Ballistics - Bullet Shape, here is the short of it.

"Therefore, because of the bullet shape, the projectile will always fly at an angle, called angle of attack, relative to the trajectory. ... Since the point of pressure is positioned in front of the center of mass, the air flow will force the bullet to rotate backward, pivoting on its center of mass."

Thanks RanchDog for your input!
Bullet maker, maker Al Nelson
« Last Edit: January 14, 2019, 03:02:30 PM by SwedeNelson »


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