Bullet Drop app questions

[obx22]

I’ve been using the Bullet Drop app, inputting parameters from Weather Radar, and a Chrony. I was recently given a simple Kestrel and when distance shooting my rimfire, the app was consistently low the farther out I shot (last on paper was 300yds.)
Trying to alter BC and Velocity to get a map that reflects actual hit is frustrating. What am I doing wrong?

 

[6.5SH]

Not familiar with the app in question but see if it lists RA4 as a choice for the BC model.

At 300+ you are where people will use an Kestrel Elite and DSF to make a more accurate chart.

 

[Tempest 455]

Just my $.02.

Most people use too high BC on rimfire rounds. Do some Google searching for this topic.
I've seen some comprehensive testing done in this area before.

 

[acourvil]

Shoot at the distances you are interested in, record the info, then play with velocity and BC until you get output that fits your actual results. Bear in mind that environmentals have a more significant effect on rimfire than on centerfire. And make sure you have good data on your rifle (e.g., scope height, zero distance, etc)

 

[obx22]

Shoot at the distances you are interested in, record the info, then play with velocity and BC until you get output that fits your actual results. Bear in mind that environmentals have a more significant effect on rimfire than on centerfire. And make sure you have good data on your rifle (e.g., scope height, zero distance, etc)

You raise a good point. If you have a slope rail (mines 40MOA on one gun, 50MOA on another) where do you measure from bore line? The turret? The objective lens?

 

[acourvil]

I do it from the center of the scope (turrets), but honestly I'm not sure if that is technically correct.

 

[6.5SH]

You raise a good point. If you have a slope rail (mines 40MOA on one gun, 50MOA on another) where do you measure from bore line? The turret? The objective lens?

 

[obx22]

Excellent