Quote Originally Posted by pjinoz View Post
Yes you can use 2 chronographs try NOT to hit the second one! I use LabRadar to determine the bc’s of my home made .25 cal slugs and have only tried one pellet;33.95 gr. JSB which computed to a bc of 0.046 using the GA function. Slugs need the G1 function ( can use JBM program), pellets ChairGun. But as others have said bc will be influenced by the velocity range and to a lesser degree gun/barrel. LabRadar will give you velocities over a range of distances and you can choose what velocity band you to measure bc. Of course the 2 chrono method could be used but with more setup time involved. On the other hand Hard Air Magazine website has many bc’s in their ballistic coefficient section and your pellet type may be included.
Cheers
The G1 drag law is not suitable for slugs, the shape of a slugs drag law is completely different to the G1 law. This is why many slugs seem to have higher BC's at high speeds. I know many manufacturers use the G1 law, but all that shows is that they don't know any better.

If the correct drag law is used, there should be very little variation in BC with speed. Most of the claimed variations are due to poor experimental technique, not correcting for atmospheric conditions and using the wrong calculators with different reference drag laws.