oldsmellhound

BC of a bullet is based on the velocity that you might be shooting it at. If you were to shoot it a high velocity the BC number may be higher than if you were shooting it at a lower velocity. Companies always publish the better velocity.

To find the real worl velocity, often people will shoot a bullet through two chronographs, one at the muzzle and one at 100 yards, then do the math to compute the real BC.

The numbers that Lee provided are probably established in that manner. From that you would need to know the load he chose to shoot it with.

Sierra bullets is the only company that I know of that provides BC's by the a spread of velocities the bullet may be shot at.

If you go here. Choose one of their bullets they will provide you a range of ballastics over the flight of the bullet.

http://www.sierrabullets.com/index.c...e=handgun&BC=1

This would be an example of a 40mm - 180 grain bullet.

Bullet NameDiameter inchesWeight grainsSectional DensityBallistic Coefficients.400 dia. (10mm) 180 gr. JHP
.400 180 .161 .140 @ 1150 fps and above
.160 between 1150 and 1000 fps
.170 between 1000 and 850 fps
.120 @ 850 fps and below

If you look on the actual Sierra site the information shown above will make more sense.