I am new to this forum and currently posting from my phone so my search ability is limited so if this has has already been answered I apologise in advance and please post a link or where I could find it. Now that I have given my poor disclosure I'm looking to find a way to determine my correct FPS. Of my particular load from my 308 that I like to load up. I have never Chronograph the round and have no access to 1 however im inclined to believe that with my reloading data my BC and length of barrel i should be in the ball park. That said I want to start pushing out to 800yds. So lets say i shoot a perfect group at 100yds to give me a good zero, then i shoot at 600-700yds using the given MOA adjustment from a good ballistic calculator. Is there a way to take the projected results and actual results and backtrack that to my starting muzzle velocity?