After reading some info on the Sierra bullet website,they stated that in the .243 cal 60gr bullets BC is higher when the velocity is between 1800-2500fps. Has anybody every read or heard of this in any other cartridge? And if so why is the BC higher???? Van

Every bullet's BC varies with velocity, how they calculate it I don't know.
The easiest way that I know of is to measure the velocity at two different places across a known distance in controlled conditions.

BC varies with velocity, because THEY USE A INCORRECT FORM FACTOR. The form they compare to is a flat base round nose (G-1), even though they are compairing it to a spitzer boattail bullet (G-7 IIRC). The number they present matches that portion of the curve, but once you go a little faster (or slower) they have to use a different # to get the curve match.

It's like trying to compare the wind drag of a Corvette using the wind drag curve of a box van for referance (when a E-type Jag's wind drag curve would be a closer model).

While all the bullet manfactures use the G-1 curve, at least Sierra is honest enough to give you several points of referance to work with (unlike Barnes who must have been using drugs when they came up with their numbers).