BC info request

01 November 2004, 07:05

Collins

BC info request

First of all, this isn't a debate about if it's good or bad or useful or not... so,

What is the relation between BC and rate of deceleration? I know that the relationship is the basis of determining BC, but has it been quantified?

I'm thinking about calculations of first shot precision using air density, BC, and muzzle velocity.

01 November 2004, 08:18

Tailgunner

BC is simply the bullet being considered vs a standard bullet (1" diameter solid, 2 ogive nose radius, etc which was assigned a BC of 1.000. The velocity loss of this bullet was determined by actual test firing). Bullets with a BC of 2.000 decelerate 1/2 as fast, those with a BC of 0.500 decelerate twice as fast, those with a BC of 0.250 decelerate 4 times as fast etc.

01 November 2004, 10:21

Jon A

Quote:

What is the relation between BC and rate of deceleration?

Inversely Proportional. The higher the BC, the slower the rate of deceleration.

01 November 2004, 17:28

JerryO

I don't know what you are trying to use the BC for, but:

I use the relationship caused by the reference projectile loseing 1/2 its energy at 1,000 yards when fired at rifle velocities, that would be around 3,000 fps. The drag goes to 1/2 or maybe 1/3 when under the speed of sound, so it won't be anywhere close when you get around 1,000 fps.

This means that a 30-06 bullet with a BC of .270 with 2800 ft-lbs at the muzzle will drop to 1400 ft-lbs of energy at 270 yards.

It also means the a 30-06 bullet with muzzle energy of 2800 and drops to 1400 ft-lbs at 450 yards must have a BC of .450.

JerryO