I'm trying to read everything I can to understand ballistic coefficient. Can someone explain to me the reason a 130 gr. nosler ballistic tip has a different BC than a Hornady SST or a Swift scirroco & which is the best, based only on BC. Thanks

The 'ballistic coefficient' of a bullet is a value that estimates it's ability to slide through the air. The higher the number the better the bullet is at handling the resistance of travelling through the air. Because of this it will be travelling faster downrange, have less drop than a lower number and buck side winds better. If you are shooting paper then the highest BC is the better bullet but if you are shooting game that rarely hold true. Also the difference in trajectory will be very small so if you are shooting 1 MOA groups your variation in groups size will be more than the difference at most shooting distances.
You are better off picking a bullet to fit your shooting needs than you are to worry about the best BC you can get.

PaulS

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stay safe and live long!

thmpr., PaulS has it right. For bullets of a specific weight and caliber,(eg., 130 grain .270), the ease with which they travel through the air is determined by their shape. Sharp-pointed ones cut through the air with the expenditure of less energy than blunt ones. This characteristic is called Ballistic Coefficient, expressed as a decimal fraction (percentage) of the ability of a "STANDARD PROJECTILE" to cut through the air, which is "1". So a bullet with a B.C. of .5 cuts through the air half as well as the STANDARD PROJECTILE.