The REALLY, real- real BC

[AlwaysLastPlace]

Edit- thanks everyone for a lot of answers. Before I posted this I did not know enough to simply ask the question any better.
So here is what (or how) I think I should have asked it:
Why does the drag law I am being told, or recommended, to use in certain apps differ?
Why does the bc on the tin not match what the calculator says it will do AND not match what I see in real life?
I have a ton of stuff to go try out now and I don't feel stuck so thanks.

P.S.
Some people are super smart and they like showing off and that can come across as talking down. But I grew up on the less fun end of a one-way range so it's pretty hard to hurt my feelings. I'm new to improving at this level, not 10 years old.
People can be any combination of wrong, right, nice or a big turd about it. It's all paying for education and now I've got homework or else I just wasted everyone's time with a less than optimal question that ya'll kindly took the time to try to answer.
I can tell you all that there are a LOT fewer and less angry know it alls in this world than in real guns, 3 gun especially. Some folks maybe should be nicer and other people maybe need to let more attitudes slide.


Guys and gals I have been doing my homework which means I have tried figuring it out on my own before bothering you fine folks.
I have a chrony built into my barrel and one at 25 yards.
I am using JSB Exact 44.75gr, a well calibrated mg scale and a brand of micrometer for head size that is so German I'd get kicked out of Disneyland (again) for saying it out loud. What am I doing wrong?
I'm getting bcs from low .03s to mid- high .04s.
I've read some things that are way too complex that I don't have equipment for, radar and such, but we have been figuring bc on paper forever.
What do I do? I intended to go through all my JSB weights and play on all the ballistics calcs to scratch my autism itch for the day but I never got past the JSB exact 44.75.
Frustrated in Fenix

 

[Scotchmo]

dgeesaman,

…(When I need to know trajectory data I shoot it and plot the holdovers manually)….

That’s all well and good for relatively short range where you are shooting under consistent conditions. But what if you want to shoot at distances well beyond what you normally shoot at, with different inclines, elevations, and environmental conditions, and you hope to hit the target on the first shot? Then you need a fairly accurate BC to predict how much compensation you are going to need.

For doing that, I think the Labradar is the best tool that is readily available for us hobbyists.

You’ve gotten to the gravy of what the Labradar can do. If you are so inclined, you can make good use of it.

 

[dgeesaman]

Here's the same technique applied to airguns.

Owing to the fact that the final 4 data points are obviously very inaccurate, I added a cell to let the user ignore a number of rows from the tail end of the data array. So you can see that also.

 

[dgeesaman]

dgeesaman,

…(When I need to know trajectory data I shoot it and plot the holdovers manually)….

That’s all well and good for relatively short range where you are shooting under consistent conditions. But what if you want to shoot at distances well beyond what you normally shoot at, with different inclines, elevations, and environmental conditions, and you hope to hit the target on the first shot? Then you need a fairly accurate BC to predict how much compensation you are going to need.

For doing that, I think the Labradar is the best tool that is readily available for us hobbyists.

You’ve gotten to the gravy of what the Labradar can do. If you are so inclined, you can make good use of it.

I've attempted to fit ballistic solver data to my Labradar data and measured holdovers. Specifically, I used downrange velocities and drop/holdover to back-calculate BC and scope elevation. The fit was never good.

As for the consistency of conditions, I use wind flags and common sense. My home range isn't very windy but it's very switchy and will blow in any direction. So it's valuable data to see the spread on target as I shoot a series of shots as the wind flags shift and move.

That said, I now see that the Labradar velocity I was feeding into that method is spurious so using the velocity regression I just put together I'll repeat the process and also try to get my hands on some ballistic solvers that have more airgun-appropriate BC models. Hopefully that combination will give me better data.

** Also, if a pellet is spiraling, would it not appear to rise/fall over the best fit trajectory? Another reason for complete manual holdover data. The other effects like air density and incline angle are predictable and can be added over either calculated or measured holdovers.

 

[Scotchmo]

I've attempted to fit ballistic solver data to my Labradar data and measured holdovers. Specifically, I used downrange velocities and drop/holdover to back-calculate BC and scope elevation. The fit was never good.

As for the consistency of conditions, I use wind flags and common sense. My home range isn't very windy but it's very switchy and will blow in any direction. So it's valuable data to see the spread on target as I shoot a series of shots as the wind flags shift and move.

That said, I now see that the Labradar velocity I was feeding into that method is spurious so using the velocity regression I just put together I'll repeat the process and also try to get my hands on some ballistic solvers that have more airgun-appropriate BC models. Hopefully that combination will give me better data.

** Also, if a pellet is spiraling, would it not appear to rise/fall over the best fit trajectory? Another reason for complete manual holdover data. The other effects like air density and incline angle are predictable and can be added over either calculated or measured holdovers.

How do you add air density over measured holdover without a ballistic app? And if you are using a ballistic app, you need a fairly close BC. At least for long shots. If your BC is incorrect, and you need to change your air density any substantial amount, the new POI predicted by the app will be incorrect.

If you’ve got spiraling, that’s a different issue.

 

[dgeesaman]

I never have and looking at the ballistic software, going from 35F to 95F moves 100y POI about an inch and going from 500ft to 5000ft elevation is about the same. So I doubt I ever will.