OK...I have to get this off my mind...So, Please bear with me...Dont know if I am looking to deep into this or if it's been mentioned before... A Sierra Gold Medal Match King .308 has a ballistic coefficient of .462 and G7 0.224... When I plug in these values in a computation in an app, it is correct...at this time...I dont debate this at all...My problem is the declared values of BC are the bullets in the box. So, my understanding is the barrel bore has grooves and lands in it. I know the bullet has to spin...I get that...After the bullet leaves the end of the barrel it's BC is totally wrecked by the lands/grooves marks on the bullets outer casing...This has got to screw with the computations...Is this variable taken into account by the app or formulas of the day. I dont know how many lands are inside a barrel and if they are consistent in all barrels. If it is different then would it complicate things even more?