As I said before, I haven't ever quite got around to calculating BCs from speed or drops; normally I've been pretty satisfied w/ the results from published G1 BCs + Exbal + Kestrel...
That said, I've always kind of wanted to, just to see what kind of numbers I do get. Probably one of those 'curiosity killed the cat' things, but I'm a sucker for those
If you don't mind me asking... did you use two chronographs or just one?
If you used two chronographs, how accurately did you measure your distances from the muzzle?
Did you shoot thru both units back to back first to see how much they differed?
The reason I ask is I have a CED Millenium (nice unit) and one of my friends has a similar unit. Note I didn't say 'identical'... I've borrowed it a few times to check mine, and one of them (I think maybe mine?) reads about 25-30fps lower than the other (depends which day, load, phase of the moon as to exactly 'how much lower').
If we did your test using these two chronographs... and the far unit was the one that reads say, 25 fast (i.e. down range velocity is really 2750fps), your computed G1 BC is something like 0.480.
If instead the *near* chrono was the one that reads 25fps fast (i.e. actual velocity was 3070fps), your computed G1 BC works out to 0.561.
I have no idea as to how to determine which chrono is the 'right' one. Some have suggested shooting match grade .22LR ammo over it which should chrono at a very consistent speed of something like 1030fps or somewhere in there. The question is, if I'm 'calibrating' my chrono using ammo that is going roughly 1/3 as fast as what I actually want to test... is my expected error 1/3 the size (~8fps) as well? Saying that chrono A reads 8fps faster @ ~1000fps than chrono B is going to be very interesting to see if you can even see that consistently.
I've probably opened a bigger can of worms than I should have here, and I'm not attempting to start a pissin' contest w/ anyone... more just kind of thinking 'out loud' about what all to consider when judging the validity of some of our 'tests'. For that matter, it's getting late, and I could be completely off-base here and just need 'calibrated' with a clue-by-four... wouldn't be the first and most certainly not the last time for that! ;)