Range Report JBM Ballestics FTE calculator for I phone question

[Arif]

i am using the JBM Ballestics calcualator in my I phone and i wanted to find out under settings we have an option to use either JBM or Ballestics to get the Trajectory calcualtion. i get slitely different results with both of them, i also use I Snipe and when i use Ballestics with identical data the results are identical with I snipe, but when i use JBM the results are slitely different, for examole .4 Mil difference in windage at 1000 yards. can anyone please tell me which one i should be using becasue i think .4 Mil is a big difference for that distance. Eevn when i use 180 degree angle for wind i get .3 Mil for windage adjustment for 1000 yards with JBM but 0 adjustments for Ballestics. I would also like to understnad what OPBZ means and what it does, and for Atmosphere which option i should be selecting, Meterologiccal/density air or density Altitude. sorry new at this and would apprecite your comments

thanks in advance

A

 

[ctressler]

Re: JBM Ballestics FTE calculator for I phone question

OPBZ = Optimum Point Blank Zero. It won't affect output, it is just a suggested range to zero your rifle at.

Which software are you running on your Iphone? The Ballistic FTE?

The JBM is the better result in my opinion. I like to use Density Altitude since that takes into account several environmental factors and all I have to input is one number. Well, two since you need to update the Mach value.

I noticed that the units of density altitude are incorrect when using the HUD, but the calcs are still correct.

The Ballistic FTE has almost too many features for the average user. You will get the most out of it if you use the zero atmosphere setting, save your load in favorites and then have the HUD load from favorites. Then you just have to enter your current density altitude and mach, choose a range and your set.

The HUD doesn't reload every time so make sure you select your round from favorites each time so you are sure what is actually loaded in the JBM.

 

[Arif]

Re: JBM Ballestics FTE calculator for I phone question

yes i am using the Ballestic FTE for my I Phone. Thank you for your comments. just could not understand why the varience in windage by using JBM even when i use 180 wind drift angle, any other calculator would say zero adjustment for wind for this angle but JBM asks me to adjust .3 MIL for 1000 yards. which direction should i adjust for if it is perfect head wind or down wind? second question what is a Mach value and how do i get it?


Arif

 

[ctressler]

Re: JBM Ballestics FTE calculator for I phone question

The Mach number is the result of dividing the speed of an object moving through air by the speed of sound. The number entered in the Ballistic FTE box is actually the speed of sound at your given temperature.

On the Trajectory side of Ballistic FTE, you can enter the current temperature and it will automatically calculate the speed of sound at that temperature.

As far as the windage issue, could it be the software correcting for spin drift, it does have that capability.

Wind angles: 0° = headwind, 90° = crosswind (right to left), -90° = crosswind (left to right). (from Jonathan Zdziarski's website)

One thing that is troubling me is the affect a headwind and tailwind have. Maybe I'm missing something but a headwind will slow the bullet down so the bullet would drop more with a headwind, but the software indicates that it actually drops less with a 0 degree wind. Any thoughts?

By the way, check out this link for details and instructions on this particular software.
http://ballistic.zdziarski.com/

 

[azimutha]

Re: JBM Ballestics FTE calculator for I phone question

Spin drift @ 1000 yards might account for
.2 mils. But mostly the difference is because the JBM engine is more accurate.

 

[Arif]

Re: JBM Ballestics FTE calculator for I phone question

thank you, ok i will stick with JBM

 

[Arif]

Re: JBM Ballestics FTE calculator for I phone question

just so that i understand correctly. so for headwind or downwind conditions i should be adjusting for opposite direction? i have right twist so i should be adjusting left for those condition becasue of spin drit

A

 

[ctressler]

Re: JBM Ballestics FTE calculator for I phone question

At this point I'm just not sure what is going on with the wind adjustments. I hope to hear from the apps author regard this.