I tested some mid-weight pellets today

[Michael]

At the Misenheimer Ranch. Figured I’d pass along my findings.

1. The True Ballistic Chronograph is super easy to setup & use. I lined it up directly beneath the muzzle and it didn’t miss a single shot.
2. Atmospheric conditions affect the BC! Use the FX Radar app and select the option “send local weather to device”.
3. If possible record data out to 100y+. The BC most definitely changes as the velocity decreases.
4. While an average BC can be useful, multiple BC points are even better.

 

[Mycapt65]

Does that thing work for powder burners?

 

[Michael]

Does that thing work for powder burners?

I haven't tried it, but it's supposed to be able to track projectiles up to 4000 FPS

 

[Ballisticboy]

The reason that the BC is changing with velocity/range is that G1 is simply not suitable as a reference drag law for pellets. The correct reference drag law should have little (most likely) or no change in BC, no matter what the velocity or range. That was the whole point in the creation of BCs for trajectory calculations.

 

[Mycapt65]

The reason that the BC is changing with velocity/range is that G1 is simply not suitable as a reference drag law for pellets. The correct reference drag law should have little (most likely) or no change in BC, no matter what the velocity or range. That was the whole point in the creation of BCs for trajectory calculations.

What drag law should be used for pellets?
Thank you.

 

[Ballisticboy]

It depends on the pellet and what calculator you are using. GA was the first reference drag law for round head pellets. There are some questions regarding its accuracy at high muzzle velocities, but it is still much better than G1. A second one for round head pellets called GA2 is also available now, which is slightly different at high speeds. For dome head hollow point pellets, use either of the above.

For wadcutter pellets there is one called WC0 which was specifically developed for wadcutters. It should be more accurate, but it still needs to be proven.

Below is a comparison between the shape of the G1 reference projectile and a typical pellet shape. To use the G1 reference drag law for a different projectile (pellet), the projectile should at least vaguely look like the G1 projectile.