Ballistic Coefficient is the bullets ability to defeat wind drag, thus hold its velocity as it travels through the air.
Sectional density is what you are referring to in regards to penetration. Also, all bets are off on SD dictating better penetration when expanding bullets are used. Though it is a measuring stick in the industry.
February 25, 2003, 11:33 PM
OH...it's aerodynamics. I understand that. I used to be a pilot, believe it or not.
So...sectional density, then?
February 26, 2003, 12:07 AM
Long thin heavy projectiles have high sectional density which means that they will tend to penetrate very well if they don't tumble or deform.
Short fat light projectiles have low sectional density.
Sectional density is one of the characteristics that figures into the determination of a ballistic coefficient (I'm not really saying that right, but I can't figure out a better way to explain it). The higher the sectional density, in general, the better the ballistic coefficient.
February 26, 2003, 12:14 AM
And how is the sectional density of an object derived?
EDIT: from the above page, the answer is: Sectional density is equal to the bullet's weight in pounds divided by the square of the bullet's diameter; SD = w ÷ d².
February 26, 2003, 02:45 AM
Sectional density then ability to defeat aerodynamic drag. I.e. pointed nose and pointed tail. As a bullets tail has to provide resistance for acceleration during the "interior ballistics" phase, Boat tail bullets represent a proven compromise. If one had a 60 inch barrel, a bullet would work better when pointed at both ends.
3 types of ballistics
1. Interior- what happens before a bullet leaves the barrel.
2. Exterior - what happens to a bullet during atmospheric flight.
3. Terminal - what happend when a bullet hits solid or liquid.
Heck, there are phd's in physics who don't get this. What do you really need to know?
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