calculating the bc of a bullet

[762plinker]

somewhere i heard that with 2 chronographs one could calculate the bc of a bullet?
if that is true could it be calculated from the down range data of a labradar ?
formula is ??
thanks

 

[Chris Edmondson]

Here's a link that may be helpful, even has a formula:

https://www.sellier-bellot.cz/en/products/ballistic-coefficient-calculation/

 

[Jarhead6870]

Kinda…some shooters will use a chronograph at the muzzle, LabRadar, MagnetoSpeed, Chrony, etc., AND something like the Shot Marker at a longer yardage where their specific bullet is still transonic. By taking the velocity at the muzzle and entering it in your ballistic program and then tweaking the BC so the bullet velocity at the target matches the average obtained from the Shot Marker, you will have a better working BC than the one published in manuals. The farther out you can place the Shot Marker, the more useful it will be as errors in BC affecting solutions are smaller at closer ranges.

This said, you are getting the BC of the bullet at only one yardage whereas custom drag curves take velocities at multiple yardages and create a curve as the bullet travels through it's velocity range. A word of caution; adjusting BCs REQUIRES that you have a zero that is dead on or adjusted with your zero height and windage offset, you have checked your scope's calibration and made the necessary change to your correction factor (if necessary) AND the yardage to the target is accurate. If any of the aforementioned are not accurate data inputs, then changing your BC will be based on invalid data and will not be as true as possible; i.e. garbage in...garbage out.

 

[whatsupdoc]

Labradar can track the velocity of a projectile out to 100 yards depending on the bullet and the
conditions.

There is a web page where you plug in the labradar tracking files and it calculates the BC.

 

[whatsupdoc]

Found it

Geladen | Labrabaco

 

[Ned Ludd]

somewhere i heard that with 2 chronographs one could calculate the bc of a bullet?
if that is true could it be calculated from the down range data of a labradar ?
formula is ??
thanks

Plug and play using Labradar velocity drop at a specific distance:

JBM - Calculations - Ballistic Coefficient (Velocity)

www.jbmballistics.com

In my hands, the G7 BC estimated values tend to be slightly overestimated, possibly due to the relatively short distances over which the LabRadar determines velocity.