iStrelok. Ballistic calculator for iPhone


Ballistic calculator for iPhone, iPad, iPod

Supports metric and imperial units! (yards, feet, inches, etc)
Supports iPhone, iPad and iPod (iOS versions from 8.0)

Field-proven accuracy since 2001

List of supported reticles (984!): here

Configuring and tuning iStrelok

Here is a video from users of iStrelok: (Spanish)

User manual

Frequently Asked Questions (FAQ)


Q. I have iStrelok in my iPhone and just bought iPad. How can I transfer my data to iPad?

A. 1. On iPhone make Export rifles to Dropbox
2. On iPad make Import rifles from Dropbox
That's it.

Q. I have Strelok+ on Android phone and have iPad/iPhone with iStrelok. How can I move my data to iStrelok?

A. 1. On Android export rifles to Dropbox
2. On iPhone. Link iStrelok to Dropbox. Dropbox/Apps/iStrelok forder will be created
3. On big computer locate file Dropbox/Apps/StrelokPlus/ Copy it to folder Dropbox/Apps/iStrelok
3. On iPhone/iPad. Start iStrelok and make Import rifles from Dropbox.
That's it.

Q. Is it compatible with airgunning as well, or is it only useable for firearms?

A. Yes, it is compatible. You can find ballistic coefficients for air rifle bullets here: Air rifles pellet database

Q. Could you try to explain how to use "truing" feature?

A. Suppose, you input muzzle speed as 2648 f/s
Shoot at distance bigger than zero distance. Suppose this is 800 yards. Calculated elevation for this distance is 26 MOA
Find out REAL elevation is needed to hit the target. Suppose this is 27 MOA.
On the trajectory validation screen input Distance as 800 yards and Elevation as 27 MOA
Tap button "Calculate" and speed at which elevation will be equal 27 MOA will be calculated. It this case, it will be 2609 f/s
Tap button "Use this velocity" and this calculated speed will replace your current cartridge speed (2648->2609) and screen will be closed.
On the main screen tap "Calculate" button and you will get calculated elevation which equals REAL elevation and equals 27 MOA
Now you can input any distance and hit the target.

Q. Could you try to explain how to use the offset relative to first cartridge feature?

A. Sight in with first cartridge in the rifle list. Shoot with second cartridge at the same distance and note vertical and horizontal offset from center. Write this values to the program. Now you can change cartridges without zeroing rifle again.

Q. Could you try to explain further about this reticle scaling ?

A. If you have, for instance, scope with reticle in second focal plane, you be able to use reticle at all magnification range not only one fixed range (as in free version).
You need to know for sure:
1. First focal or second focal reticle you have.
2. Min. and max. magnification your scope.
3. If your reticle is placed to second focal plane you need to now magnification the reticle was calibrated for (Scope manufacturer usually specifies in the manual "power setting for using the ranging features". Use this zoom.).
Tap the "Settings" button on reticle screen and input this values.
After you can set the magnification you prefer and my program will scale reticle dimensions and calculate holdovers for this magnification. No changes in physical dimensions will occur but if you move slider left and right you can see the holdovers changes.

If you doubt which focal plane your reticle is placed, leave the checkbox "This reticle in the First Focal Plane" in checked state.

Q. Am using a Leupold 8.5-25 scope with the varmint reticle
What ranging magnification should I use to get accurate results in your app?

A. 1. On the "Reticle" screen tap "Settings" button
2. Find on a scope power selector a big triangle. Look what magnification it corresponds. Set this magnification as "Ranging magnification".
3. Set 8.5 as "Min. magnification"
4. Set 25 as "Max.magnification"
5. Return to "Reticle" screen, select any power you want of you scope, select the same power in the scope, read holdovers from reticle and shoot.

Q. Any plan to add "Truing" feature?

A. Already included.

Q. What is your definition of "scope height"?

A. Distance between center line of scope and center line of bore. Like here.

Q. What is difference between MilDot (USMC) and MilDot (US Army)?

A.Read this good article: The Truth About Mil Dots

Q. Would it be possible to support reticle duplex for hunting rifle?

A. Sorry, but duplex reticle has no subtensions, so calculate holdovers is not possible. Without holdovers the presence of this reticle in my program does not make sense.

Q. Where is cartriges base?

A. Coming soon. You can find ballistic coefficient for your bullet here

Q. Why I can not hit the target with your ballistic program outputs?

A. Read this good article: Sources of Ballistic Program Inaccuracies

Q. Which drag function used in the program?

A. G1.


Click to download iStrelok on App Store



Explanation of terms:

1. Zeroing weather:
Weather at which you zero the rifle (scope) in

2. Zeroing weather: match current weather:
Weather at which you zero the rifle in match the weather you shoot the range
Another words, you zero in the rifle and shoot the range at the same place and time

3. Zeroing weather: enabled (disabled):
If zeroing weather enabled, the program will consider a difference between zeroing weather and present weather.
If zeroing weather disabled, the program will consider that zeroing weather and the present weather are identical.

4. On how many percent bullet speed will change at change temperature on 15 degrees:

Suppose, you have 2 bullet velocity mesurement. 1 and 2 (for different temperatures):
TempDiference = temp_2 - temp_1;
SpeedDiference = speed_2 - speed_1;

TempModifyer = SpeedDiference/TempDiference*15/speed_1*100;

TempModifyer - this is parameter we need for input to my ballistic calculator.

Here is simple calculator for this purpose: metric units, imperial units


MOA - minute of angle

MIL - miliradian.

clicks - clicks of scope knob

Hor. - Horisontal adjustrment

Vert. - Vertical adjustrment

See also: Strelok for Android, Mac OS X

E-mail me: (russian, english)

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