Ballistic calculator help.

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Bryan Carvalho

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I've got a couple calculators downloaded to my phone and I'm getting some different results. What is everyone using for a calculator? If someone could punch my numbers into their calculator I'd appreciate it.

308 win
1:12
175 berger otm (.512 G1 .263 G7)
Avg. 2689fps
My elevation would be for barrie on. (Can't remember what it is)
Sight height is 1.89
Looking for dope in mils. I'm getting about a .4 difference at 500 yards between calculators. It's a new load for this gun and I'm going to run it at 100-500 soon and won't have a chance to run some tests...sort of just thrown into a match so to speak. Thanks for any help.
 
I run my data on JBM as well but then check in the field to see if dopes correspond correctly from real world to what the program spits out.
 
What I do:
Shoot consitent quality ammo (reloaded!) with a chronograph at 200Y, zero my rifle.
I shoot multiples rounds, I note carefully all the temperature / environment data. I make an avreage of the velocity as a guide.
Then I switch to 500Y target. Once I got the real drop, I write it down, with all other data observed.
When I go home, I run these data in a Ballistic calculator, with the BC gived by the bullet manf. Usually there is a little mismatch between the ballistic program and the real drop at 500Y. To make them match, I change the BC of the bullet around until there is a match wioth the real life and the chart. I print it out, and try it back on the range at 300Y, 400Y and if possible farther. If the temperature and atmospheric conditions are very similar (and the same range or same altitude!) the printed chart should match very closely.
Bingo, you have a chart that work AT THIS GIVEN TEMPERATURE. If the temperature change, the powder will change so not only the air temperature will affect the bullet fly path, but the powder will burn slower so the velocity will change also. So you can anticipate your velocity with a chart that estimate the velocity with given temperatures, or you do it yourself with your chronograph at différents temperature during the year and make yourself a burn rate curve that you use to make some different charts for each temperature brackets. It is easy afterward to interpolate the results between two températures.

Dark
 
I use Ballistic AE and have found it gives me great dope, after I trued up the muzzle velocity using dope observed near transonic (800 yards-ish). Have used it to make hits out to 1140 with my .308 in many different environmental conditions. Try JBM online, that's the solver Ballistic AE uses.

You're going to need better environmentals though if you expect accurate results. That being said, 500 isn't all that far and looking at my charts I only need 0.2 mils more elevation for 500 yards going from 0m of density altitude to 1500m. Other than the data you provided, what you'll need to get good dope is the density altitude you zeroed at (or altitude, barometric pressure(not station pressure) and humidity) as well as the temperature you zeroed at and the temp you measure your mv at as well the muzzle velocity variation for the powder you use (or you can use some standardized curves). Plug all that in and you should get decent dope. Hate to say it but the only way to get great dope is to go out and test what the calculator tells you in the real world and true up the program so things match...
 
Strelock Pro has some really good reviews. Works on your mobile. In fact, in all the looking for a ballistics calculator I've done, nobody is really negative about it - I have gotten it myself, and not pushed it past 300 yards. Being a novice, it was getting me on a 12x12 board. I have even communicated with the author of the app, and he really believes in his product and is continually improving upon it. The feature I really like the most, is that it actually has the reticle for countless different scopes from many manufacturers, and it will show you the exact hold, with zoom adjustments as an interactive display if you wish to not use the scope adjustments. I've played a little with that as well, and it would get me on target. It was about $20 for the full version, come spring time I will sit with it for longer periods at a more relaxed pace to really see what it can do.

Checking it out is just a google search away.
 
Bumping this thread because I ran in to the exact same problem of ballistics calculators disagreeing despite the same data going in. I was using these two:

http://gundata.org/ballistic-calculator/

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Between these and Strelok and others, has anybody done an actual field test to confirm the models used by the ballistics calculators out there?

Regardless, thanks for the suggestion from Evil_Dark, that's a solid idea.
 
I was using Applied Ballistics Mobile last weekend and comparing it to Ballistics ARC which uses JBM. Drop predictions were the same and accurate, but we only shot to 500 yards.
 
Evil_Dark said:
What I do:
Shoot consitent quality ammo (reloaded!) with a chronograph at 200Y, zero my rifle.
I shoot multiples rounds, I note carefully all the temperature / environment data. I make an avreage of the velocity as a guide.
Then I switch to 500Y target. Once I got the real drop, I write it down, with all other data observed.
When I go home, I run these data in a Ballistic calculator, with the BC gived by the bullet manf. Usually there is a little mismatch between the ballistic program and the real drop at 500Y. To make them match, I change the BC of the bullet around until there is a match wioth the real life and the chart. I print it out, and try it back on the range at 300Y, 400Y and if possible farther. If the temperature and atmospheric conditions are very similar (and the same range or same altitude!) the printed chart should match very closely.
Bingo, you have a chart that work AT THIS GIVEN TEMPERATURE. If the temperature change, the powder will change so not only the air temperature will affect the bullet fly path, but the powder will burn slower so the velocity will change also. So you can anticipate your velocity with a chart that estimate the velocity with given temperatures, or you do it yourself with your chronograph at différents temperature during the year and make yourself a burn rate curve that you use to make some different charts for each temperature brackets. It is easy afterward to interpolate the results between two températures.

Dark
Click to expand...

that should put as a sticky: very well explained and still simple.

well done and thanks a lot.
 
I use bulletflight, it's not free but seems to work well. I chronograph my rounds first then plug the data in and shoot at 600 yards and adjust my velocity in the program until it gives me my actual adjustment to make the hit(my chrony sucks). Then I just push it out from there to make sure it's consistent. I usually try to validate it to at least 1200 yards depending on the weather
 
What Dark said plus my .02

I think you still need to "true" the curve your calculator is using no matter what model, and as others have stated as soon as temperature or another environmental factor changes so does your drop. I was at a course in Texas last week and we used the Kestrel 5700 with Applied Ballistics for the class, and I also had the Horus Atrag on a Recon of my own. We zeroed at 94m and then "trued" at confirmed 800m.

Even with all the environmental plugged in (temp, baro, humidity-DA), my rifle (308 FGMM 175) used 8.1 mils instead of the predicted 8.4 mils that either one of these devices predicted. Using the trueing feature on either program it adjusted the velocity until the curve matched. Was my velocity actually what the program used-probably not as it ended up being 2680 for Federal Match which I doubt (24" barrel), but regardless it made the necessary correction for the predicted curve to match the actual curve.

The take away from the class was provided you had a distant object, even a rock that you could confirm was at distance close to transonic for your cartridge, you could firm up your longer range zeros in the field without the need for a chronograph.
 
Astute Observer said:
Bumping this thread because I ran in to the exact same problem of ballistics calculators disagreeing despite the same data going in. I was using these two:

http://gundata.org/ballistic-calculator/

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

Between these and Strelok and others, has anybody done an actual field test to confirm the models used by the ballistics calculators out there?

Regardless, thanks for the suggestion from Evil_Dark, that's a solid idea.
Click to expand...

I do the same field test as evil dark with the exception of - I change the bullet velocity to match the program to actual results and leave the B.C. Set
 
Well Bryan; I have two on my phone that where recommended.
1st was Ballistic Advanced Edition which seams to be pretty user friendly but I have not tested it out at any great distance.
2nd Recommended to me by a PRS shooter is GEO Ballistics.
He has been using this one for a while and reports that it is "spot on".
I can get you the first one at a discount if you like.
SRSA311
 
Whenever you use one of these the first thing you should do is read whatever material they have with it that explains how it's calculating and what "variables" you can load.

Things like wind direction, wind speed, humidity, temperature etc that all effect trajectory may be "constants" in one program but not another (and they may not use the same values for those constants) - just depends on the complexity of the software.

Of course the best software in the world is still only going to give you an "almost, nearly, but not in all cases". It might be super close to "your reality" but you have to spend some time shooting to recon any error that may apply to your set-up.

I use Strelok mostly but sometimes Hawke Ballistics.
 
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