Very useful stuff, Bob. BC is obviously one of the key parameters we have to estimate to calculate trajectory, and it's quite elusive and of course it's a variable. One question I have is what units are associated with the BCs in your table. In the ChairGun database, and everywhere else I look, I see only a number and no units. To add further confusion, the BC shown in ChairGun doesn't change when you switch from imperial to metric units. Of course the conversions could be handled internally by the software and the ChairGun outputs are likely correct, but it still begs the question... What units? Since all the articles I have read (admittedly on-line, like Wikipedia) use imperial units ft, fps, fpe, in, gr, lb... etc. do they all imply BC are measured in lb/sqin?