Looked at your profile
Don't Know how to put up a profile of my own so:.I am a retied Electrical/electronic engineer. More importantly I am a Brit and don't own guns although I'm very interested. I wanted the formula so I could do in my head what you can do in practice (with your chrono). Somewhere on this sight I found a link to a site which calculates Muzzle velocity but needed "a published load", case capacities, lengths etc, and gave no formulas. When I tried to use it with what Info I had it seemed very inaccurate. It gave a velocity which was supposed to be 65% of the shots. The string deviation was always about 50ft/sec or more above and below the 65% value. I always thought published figures were about average for a string, perhaps plus or minus 25-30ft/sec.