My ideal ballistic calculator. Is it already made?

[Monkeyleg]

In another thread I asked about ballistics calculators, and got several suggestions. I've downloaded some of them, and looked at others online. Some are simple (Hornady's) and some involved (JMB).

All of them, though, give approximate come-down figures that are very similar to each other, but not to real life. For example, today I was shooting at 200 yards at an altitude of 1600 feet, 47 degrees, 50% humidity, and pressure of 30.14. All of the calculators give a drop of 4.11+/- .10 from my 100 yard zero.

The actual drop today was 5.5 inches. The drop the other day when it was 69 degrees and 70% humidity was 4 inches.

To my way of thinking, the ideal calculator would allow you to replace the come-down numbers and windage numbers with the actual numbers you find necessary under various conditions, and then adjust other distances accordingly.

Is there any such animal available?

 

[MCMXI]

Is there any such animal available?

ExBal (from Nightforce) has a trajectory validation option which allows you to enter "real world" corrections as either actual scope/sight adjustments or error on target. The software calculates the average error and actual velocity if the values converge. Convergence simply means that the trajectory of the bullet is valid. For example, the bullet can't suddenly gain altitude. Anyway, if you click "apply", the new MV will be applied to the ballistic table. Here's an example using data from the library for a .308 Win FGMM 168gr load. You can see how the calculated MV is 2,521 fps after entering the corrections and the ballistic table has been updated to reflect the new comeups.

 

[MCMXI]

today I was shooting at 200 yards at an altitude of 1600 feet, 47 degrees, 50% humidity, and pressure of 30.14. All of the calculators give a drop of 4.11+/- .10 from my 100 yard zero.

The actual drop today was 5.5 inches. The drop the other day when it was 69 degrees and 70% humidity was 4 inches.

Don't worry about humidity. It has very little affect on bullet drop or drift. Density altitude is the important variable along with wind of course.

 

[Norrick]

i think vortex optics website has a ballistic calculator that allows you to make compensations for real world conditions vs. theoretical calculations. I tried using it but couldn't get it to work. I don't know if the website isn't working properly, or if it was my browser.

http://www.vortexoptics.com/content/lrbc

you would need to register to use it

 

[sscoyote]

I've used JBM often to calculate and troubleshoot trajectories, oftentimes using various models based on G1-G7 drag functions. I can get very close by adjusting drag function often.

 

[Sensai]

A 1.5 inch POI shift for a 22 degree temperature change seems a little extreme for extenal ballistics alone to account for. The only time that I've had that much change was caused by a temperature sensitive powder. Of course none of that has anything to do with your question!

I use the Quickload software program for internal ballistics for reloading, so I naturally migrated to the QuickTarget external ballistics program that comes with it for external ballistics computations. You can customize either/both for your gun(s). I can't complain about the performance of either program, but they are definately NOT free.

 

[briansmithwins]

Monkeyleg, where are you getting your SD and muzzle velocity numbers from?

BSW

 

[Monkeyleg]

briansmithtwins, I'm getting the muzzle velocity from my chronograph. I'm also brain dead this morning. What's "SD"?

 

[briansmithwins]

I was thinking Sectional Density when I should have been thinking BC or Ballistic Coefficient.

Apparently I shouldn't post before I finish my first cup of coffee.

BSW

 

[Monkeyleg]

Sierra has sectional density data for all of their bullets. For the BC, Sierra gives three different coefficients depending upon velocity. Come to think of it, the ideal calculator would allow you to change the BC for different velocity ranges, because the BC is going to change as the bullet slows.

 

[taliv]

best i can figure, it's not the calculator that's the problem, it's the input. specifically, I think almost all the published G1 BCs are worthless. I've had very good luck with Litz' G7 BCs matching real-world experience.

 

[MCMXI]

I think almost all the published G1 BCs are worthless. I've had very good luck with Litz' G7 BCs matching real-world experience.

This was certainly the case for the 178gr A-MAX that I use. I had to contact Hornady directly to get the actual BC for "typical" .308 Win MVs. It's quite a bit higher than the commonly published data. Sierra provides three BC values for their match bullets whereas Hornady publishes an average over some velocity range.

 

[Offfhand]

If you already have the QuickLoad loading program, a smart imvestment is the companion QuickTarget program. Whatever caliber, load, bullet you're working on with the QuickLoad is transfered to QuickTarget and you get detailed external ballistics. Both programs are well worth the money and then some.