Convert a drop chart for different weather and elevation?

[Seeking_Coyotes]

OK. I go out and shoot my rifle at known distances, establish precise elevation scope dial positions for each distance. Well, it's 80 degrees. How do I convert this data to 20 degrees and at different elevations, etc.

 

[Mozella]

In simple terms, put a ballistics app on your smart phone, input the data for your zero conditions, and then when conditions change input the new temperature or altitude and the app will tell you how many clicks to adjust your scope.

 

[DocUSMCRetired]

I don't know how in depth you want to get, but you can use formulas to convert atmospherics between temp variations, or altitude variations.

 

[normmatzen]

Actually, you can do what I do. Buy a WEATHERmeter by Weather Flow then get the app for BallisticART. The combination does all the wind and weather data as well as Density Altitude, temp, humidity. Then, check the ballistics chart for come-ups!

 

[Ned Ludd]

Just out of curiosity, do any of these apps take the change in load velocity caused by changing temp into account, or only the exterior ballistics? If not, any change in velocity is another factor the OP might want to include when establishing drops over a wide range of temperatures.

The last year or so I have been measuring velocity for competition loads religiously, over as many different temp conditions as I can. The main reason for this is so I can decide for myself whether the velocity changes predicted in Quickload for changes in ambient temperature match the actual velocity changes I record. Through this process, I'm finding that there is more variability in velocity due to temp change than I had previously thought. For example, one of my .308 Varget/185 loads is dropping by an average of ~10-12 fps going from the mid 90s to low 60s. That's not enough to create any issues when shooting at 600 yd. However, it might well be an issue with almost twice the temp swing (80 to 20 degrees as the OP mentioned) and shooting at 1000 yd. Varget has a well-earned reputation for minimal temperature-sensitivity, but "minimal" is not "zero".

 

[CharlieNC]

Yes the app I use lets you account for the ammo temp effect. Specify velocity at a given temp plus the sensitivity factor, and the result at the current condition is calculated and used for the trajectory input automatically. Adjusting the sensitivity based on shooting various seasons has helped me fine tune my shooting without actually measuring it.

 

[Ned Ludd]

Thanks - that's useful to know. Although the temp predictive features of QL don't seem too far off, I'm not yet convinced it's good enough to use for adjusting competition loads based solely on predicted temps.

 

[Kings X]

Yes the app I use lets you account for the ammo temp effect. Specify velocity at a given temp plus the sensitivity factor, and the result at the current condition is calculated and used for the trajectory input automatically. Adjusting the sensitivity based on shooting various seasons has helped me fine tune my shooting without actually measuring it.

I guess I missed the name of the App you are using.
Thanks

 

[Milo 2.0]

I guess I missed the name of the App you are using.
Thanks

All apps will let you do it just by creating diff profiles for conditions.
Plus the Kestrel 5700 with link ballistics has almost negated the need for temp stable powders if a guy puts the effort into it.

 

[fredo]

Screeshot of my Ballistic AE App, under the "Reloading Data" sub-menu on the TRAJECTORY screen:

Note: that 'Sensitivity' field is set to 0.5, for Ramshot Big Game.
That translates to 0.5fps/1°F, and was determined via Magnetospeed measurements during Summer & Winter.
IE:
avg. MV @ 80°F = 4085
avg. MV @ 30°F = 4060
that's 25fps velocity shift for 50°F temp swing
Viola, 0.5 fps/1°F

The AE app recognizes any temp difference between "zero temp (atmosphere)", and "current temp (atmosphere)". Then, it calculates & adjusts MV according to the 'Sensitivity' value...

Easy peasy. There is no need to save separate profiles for the same rifle/load @ different temps with AE
Only thing that takes time is determining an accurate value to input in that 'Sensitivity' field...

Hope that helped clarify?

 

[fredo]

And here's a screen shot of 'Calculated Trajectory' screen.
Note: I inputted 20°F as 'current temp, in order to show the 'Sensitivity' feature adjusting MV:

Zero temp was 72°F , MV 4085fps.
See how the program adjusted MV DOWN to 4059fps, to compensate for the 20°F 'current temp' in entered?

Works like a charm!

BTW, does the same for atmospherics/pressure/DA. As long as you enter accurate data, the program will compensate for it by recognizing an difference in 'ZERO' conditions to 'current' conditions....

 

[CharlieNC]

I guess I missed the name of the App you are using.
Thanks

Richard I am using the old, free version of Strelok. Not perfect and I will upgrade once convinced improved calcs are implemented.