What are "break velocity" and "retard. coeffic. rate"?

[Monkeyleg]

In another, older thread there's a link to a ballistics calculator for Blackberry devices. I downloaded it, and it does a lot (especially for free).

There's several fields in which to enter variables (BC, bullet weight, temperature, zeroed range, etc), and those I understand.

There are two fields that require numbers for variables I don't know, and can't seem to find anything anywhere about them.

One is "break velocity". I saw something in Wikipedia that made me think I understood, but then I realized I don't.

The other is "retard. coefficien. rate", which I assume is an abbreviation for something like "retardation coefficient rate". I have no idea what that is or what it might be.

Does anyone know what these would be, and where to find the values, or if there are just rough "stand-in" values for these two?

Thanks much for any replies.

[dodgefan]

Try googling Pejsa ballistics.
I would put 1200-1300 for break velocity and .5 initially for retardation coefficient.