As far as Apps go, I have Ballistic AE and KAC's Bulletflight on my iPhone. I find I prefer Ballistic AE more because its more customizable and it also has a good factory load database for those rare occasions when I am shooting something factory and want to get in the ballpark.
If you want free, I highly suggest you just use the JBM link above and print out your ballistics for each load the night before going to the range.
Remember, like anything - its always GIGO (garbage in, garbage out). You need accurate input data before you have any hope of getting a decent output.
Couple of things you will need:
- Measure your sight height. measure from center of tube to center of bore. Easiest way I've found is to measure from the center of your windage knob to the center of your receiver chamber.
- Have an accurate MV. If you are shooting reloads and don't have a chronograph, you'll have to guess. But I'll bet you can find something close to your load that someone has posted which will get you very close. Even if you find a load that matches but the barrel length is off - the normal Rule of thumb is +/- 25 fps for each inch of barrel difference. If factory loads, you should be able to get that from the company's website and then extrapolate using the 25 fps ROT.
- Pick the correct bullet and BC profile. G1 is fine, G7 Litz is better.
- know the environmentals. You will need elevation (altitude) of your shooting range (try google earth), temp, baro pressure, and % humidity. The Weather channel or Aviation websites are good for that.
- Wind. I would put in a 10 mph full value wind (90 deg or 3/9 o'clock crosswind) to give you a benchmark to adjust from depending on the wind you see out there on the day. Then when its different, you can easily adjust up and down. e.g. a 5 mph wind is half the correction and so on....
I would ignore for now all the sight offset, zero height, cant, etc BS data fields.
Finally make sure to match your outputs to what your scope knobs are calibrated in. For instance, make sure the elevation and windage output is in MOA if you have MOA knobs.
The bottom line is don't overthink it. At this stage, the calcs are to get you on paper at 600 yds. So they don't have to be perfect. What you REALLY want to do it then build your own dope from what the bullet tells you.
