Bc sd ?

[1911guy]

At the top right hand corner of each load in my Lyman Handgun Reloading Manual is a BC: and a SD: with a 3 digit number out beside each of them. Can someone tell me what these mean.
I can't seem to find out what these represent. thanks

 

[NWSharpshooter]

Balistic Coefficeint is a measure of how much resistance a bullet encounters in flight. It not only determines how fast the bullet slows down, but also how much it is affected by cross winds.

Sectional density is a measure of a bullets mass in relation to it's cross-sectional area. It gives a good idea of how well a bullet penetrates targets.

For the reloader, you should know terms like:

Resizing, case trimming, seating depth, pressure (PSI and CUP), spitzer, flat-base, ogive, neck tension, cannelure, headspace, load density, burn rate, berdan primed, flash hole, and others I may have missed......

 

[1911guy]

So this is ballistic info for the projectile and not anything to do with loading. thanks for that!