Knowledge Base

Kestrel 5 Series Ballistics

Kestrel 5 Series Ballistics
Learn more about the how to use your Kestrel 5 series ballistics product

4DOF is a ballistics engine created by Hornady for their bullets as well as other common long range bullets made by other manufacturers. The 4DOF solver utilizes a modified point mass solution which models bullet flight in 4 degrees of freedom to provide incredibly accurate trajectories to extremely long ranges. The software does not use Ballistic Coefficients (BC), but instead utilizes Drag Coefficient versus Mach number data measured with a Doppler radar for each projectile. While the 4DOF solver does not use traditional ballistic coefficient numbers, the Kestrel 5700 with Hornady 4DOF also includes a traditional G1 & G7 ballistics engine for use with bullets which don’t have a 4DOF bullet file available.

Hornady 4DOF Solver... Read more

Due to differences in barrel machining, muzzle breaks, propellants and other factors, when the same bullet is fired from different rifles there will be a slight difference in the drag the bullet will experience. The Hornady 4DOF solver assumes the bullet will be fired from an "average" barrel but in reality your rifle may impact the bullet slightly differently. To account for any differences the Axial Form Factor value can be modified to align the output from the solver to what your bullet is experiencing. By firing at a known target and adjusting the Axial Form Factor value till the predicted solution matches real world results, you can calibrate the solver to match your rifle and bullet and deliver even more accurate firing solutions. Axial Form Factor can be calibrated using a target anywhere from 300 to 800 yards away and impacts the solution through the supersonic, transonic, and subsonic flight of the bullet.

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Zero range is the distance from the muzzle to where a straight line following the axis of your scope crosses the flight path of the bullet. The scope is typically adjusted so this crossing point happens at 100yds but can be set further out. Because the flight path of the bullet can be impacted by changes in environmental conditions, the distance to that crossing point can vary with altitude or changes in the weather, notably if longer distance zero ranges are used. Zero Angle on the other hand is a measure of the angle between the straight line following the axis of the scope and the straight line following the axis of the rifle barrel. This angle is very small and would be difficult to measure directly but the 4DOF ballistics engine can find the angle when provided with environmental data and bullet impact location. Once the solver knows the Zero Angle between your rifle and scope a very accurate solution can be provided regardless of how long the zero range is or how much the weather changes. Read more about the Hornady 4DOF ballistics engine.

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Zero Angle is available but it is not the default option. To find Zero Angle in your Kestrel, enter the gun menu and scroll down to Zero Range (ZR) and press the center button. In the Rifle Zero sub menu, highlight Zero Range and toggle left or right. Zero Range will change to Zero Angle and a Calibrate Zero Angle command will appear below it. Selecting Cal Zero Angle will open the Zero Angle Calculator tool.

In the Kestrel LiNK Ballistics app, enter the Gun Profile Editor where you build profiles and tap the Zero Range field name in yellow. In the pop up you will see an option to switch to use Zero Angle.

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Because not all laser rangefinder manufacturers use the Kestrel Ballistics Bluetooth Protocol to talk to a Kestrel, the Hornady Kestrel cannot communicate with some rangefinders which can talk to our existing ballistics meters. The Hornady Kestrel can currently communicate with the following rangefinders.

  • Leica Rangemaster CRF 2800.com
  • Vectronix Terrapin X
  • Bushnell Elite 1 Mile CONX

If you have a laser rangefinder with Bluetooth LE which you would like to have communicate with one of our Kestrel meters please contact the manufacturer and ask them to implement the Kestrel Ballistics Protocol in their rangefinder.

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When calculating Zero Angle, the Hornady Kestrel asks for the distance to the Zero Target. This distance can be any distance you want but you’ll want to pick a distance where you’ll be able to accurately measure the distance between your point of aim and average point of impact with no elevation dialed or held when shooting. 100 yards or meters is a convenient distance and may be close to where your rifle is already zeroed.

Note: Just because your shooting range says a berm is at 100 yards, you should still confirm that distance with an accurate laser rangefinder or 100 yard tape measure.

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After entering the Zero Angle sub menu, select Cal Zero Angle and then follow the prompts to enter the required data for your shooting environment and target. When shooting at your zero target, make sure your scope turrets are dialed to zero elevation, don’t hold any elevation in your reticle and place the cross-hairs directly on the target (point of aim). After firing enough shots to be confident of your average point of impact, measure the distance between your point of aim and average point of impact. Enter this value in the Cal Zero Angle calculator field asking for the Impact Height at Target, (impacts above the point of aim are positive and below are negative). After calculating the Zero Angle, press Exit and when prompted, accept the Zero Angle value.

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The Kestrel LiNK Ballistics app works with all of our Kestrel Ballistics meters. It recognizes the exact meter that you are currently connecting and changes to match that Kestrel.

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Please check out our tutorial:

Kestrel 5 Series Troubleshooting Documents

Find answers to common Bluetooth connection issues

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Please see this guidance:

Kestrel 5700 with Hornady 4DOF Downloads

Guidance on how to properly adjust your Axial Form Factor

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Please see this guide:

Kestrel 5700 with Hornady 4DOF Downloads

This guide covers explaining Temperature Sensitivity Coefficient and how to enter through Kestrel LiNK Ballistics app or on Kestrel itself.

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The attached links will help with determining average wind direction and the use of a wind rose. The documents would be pertinent to any of the 5500 models, especially important for spray drift and measurements in the protected zones.

Kestrel 5 Series Downloads

The attached document in Excel will help with determining average wind direction and the use of a wind rose by using the exported CSV file. This would be pertinent to any of the 5500 models, especially important for spray drift and measurements in the protected zones.

Kestrel 5 Series Downloads

How to Figure out Average Wind Direction with a Kestrel 5000 Series Unit.

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You will first need to create an account if you do not already have one. After you create an account, sign in. Click on your account name at the top of the page and select My Account. On the left of the screen, you will see Product Registration, select this option. Enter your purchase date, serial number and product name into the fields and then select Save.

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A bullet file is the exact physical model of the projectile that includes the bullet's mass properties, aerodynamic moments and Doppler Radar determined drag coefficients. By having the exact shape and mass distribution of the bullet along with the aerodynamic moments and drag coefficients for that specific bullet, 4DOF can accurately model the dynamic flight characteristics and provide an incredibly accurate trajectory solution. This exact modeling of the projectile allows us to predict drop, wind drift, projectile Gyroscopic Stability Factor (Sg) as a function of range, yaw of repose and corresponding prediction of spin drift, aerodynamic jump due to a cross wind, and limit cycle yaw at extended ranges due to Magnus effects.

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Please see this guide:

Kestrel 5700 with Hornady 4DOF Downloads

Quick guide on connecting a Kestrel 5700 with Hornady 4DOF to the Kestrel LiNK Ballistics App

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Please see this guide:

Kestrel 5700 with Hornady 4DOF Downloads

Quick tutorial on how to create and transfer gun profiles for Kestrel Hornady 5700 4DOF units

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Please see this guide on how to update your Kestrel Firmware using Windows:

Kestrel 5 Series Troubleshooting Documents

Tutorial on how to update your Kestrel 5000 series firmware using LiNK for Windows.

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Please see this guide for updating Kestrel 5000 series units with MAC/OSX:

Kestrel 5 Series Troubleshooting Documents

Tutorial on how to update your Kestrel 5000 series firmware using LiNK for MAC/OSX

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If you are getting NaN shown as a solution, then you have a bad value in your gun profile. For instance, the bullet length is set to 0.000. This also confirms that you have an older version of the firmware as later versions will check for these conditions before loading the gun on the unit. Check your profile and update your firmware to resolve this issue. If you are getting Bad Enviro as a solution, then there is an issue with one of the sensors. If the issue persists, then there might be a sensor failure. The best course of action is to fill out a Kestrel Service request and send it in.

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Var is going to be the magnetic declination of your current location, further information can be found here: Magnetic Declination
Var is not used when selecting Magnetic North. If you choose True North, then it is advisable to add the Var number.
To find your magnetic declination, here is a good place to start Find my Var

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Make sure Bluetooth® is turned ON on your phone. On the Kestrel, go to the Main Menu->Bluetooth and turn it ON. Press the center button while Bluetooth is highlighted and check to ensure that Conct is set to PC/Mobile and it shows Available. Next go to the application that you are connecting with on your phone and select the Kestrel as the device you would like to connect with. Please note: if you do not find the Kestrel on your phone’s “standard” Bluetooth connection screen, that does not mean that the Kestrel is not working properly. Please first go to the application and try to connect through the application. The Kestrel should connect.

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As can be seen in the pictures below, place your thumb on the bottom of the unit and slide the latch from the “Locked” to the “Unlocked” position. The battery door should pop up enough that you can remove it. If you have trouble opening the battery door, some slight pressure DOWN on the battery door itself with your other thumb may help release the latch.


Opening the Kestrel Battery Door ... Read more

First slide in the tab at towards the top of the unit, then gently press the bottom part of the battery door down until it snaps into place.  Ensure that the O-ring remains in place on the battery door when closing.

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NK strongly recommends continual use of Lithium AA batteries in your Kestrel.  Lithium batteries respond best in extreme temperatures and help prevent against any corrosion.  Customers can also use Alkaline or Nickel Metal Hydride (NiMh) if they prefer, but we recommend turning “Auto Store” to “OFF” when placing these units in storage to minimize the drain on the battery.  Also, please make sure you set the System->Battery setting to match the type of batteries that you are using.

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The Kestrel 5 Series models can store over 10,000 data sets.

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Wind Speed – NK sells factory calibrated replacement impellers that can easily be installed by the customer. NK recommends replacing the impeller every 2-3 years depending on usage.

Humidity – The Kestrel 5 Series and DROP data loggers employ a highly accurate, calibrated, digital humidity sensor. Based on the sensor manufacturer's specifications and NK testing, drift on this sensor over time is minimal and field recalibration is likely to degrade accuracy rather than improve it. Factory calibration to validate and certify accuracy at a minimum of two RH points is available from NK. In the event NK observes a significant number of tested sensors exhibiting drift greater than +/-1%RH/year, NK will develop a recalibration routine which can be installed via firmware update. During the five-year warranty period, NK will repair, recalibrate or replace any Kestrel 5 Series or DROP which drifts more than +/-1% RH/year since the date of manufacture.

Temperature – The thermistor in the Kestrel 5 series should not need to be recalibrated. If you think your sensor is incorrect, please contact techsupport@nkhome.com

Pressure – The pressure in the Kestrel 5 series should not need to be recalibrated. If you think your sensor is incorrect, please contact techsupport@nkhome.com

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Kestrel 5 series units with LiNK will need to use the Kestrel LiNK Wireless Dongle to connect with a computer. The Kestrel 5 series will not work with any internal Bluetooth modules. To connect, insert the Kestrel LiNK Dongle into an open USB port. On the Kestrel, go to the Main Menu->Bluetooth and turn it ON. Set Conct to "PC / Mobile." Open the application on the computer and select the Kestrel as the device to connect to. There is no more “pairing," "COM port numbers," or "PIN Codes" to worry about for those familiar with the 4000 series.

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Please see our guide for this Bluetooth issue:

Kestrel 5 Series Troubleshooting Documents

Get help connecting my Kestrel 5 series unit to my computer using a bluetooth dongle.

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Please see our graphing guide:

LiNK (Kestrel)

This tutorial will show you how to create a graph of the data that you exported from your Kestrel 5000 series or Kestrel DROP using one of the Kestrel LiNK applications.

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The free Kestrel LiNK Ballistics app for Android and iOS is the ideal companion to the Kestrel 5700 Ballistics series of Weather Meters. Build and manage your gun/bullet profiles and download them to your Kestrel Ballistics unit before you set out. The app is also the perfect way to display your ballistic solutions remotely via Bluetooth.

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Our article Understanding Pressure, Altitude and Density Altitude talks about Altitude and Barometric Pressure in great detail. The article also describes how to utilize your Kestrel to take these measurements.

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The true distance to target should be entered, as reported by a laser range finder or whatever other means the operator is using to get range to target. See below:

Angle of Inclination

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Reference Altitude and Reference Baro have no impact on your ballistic solutions when using the Kestrel's internal solver.

If you are using an outside application to solve for the ballistic solution, it is suggested that you leave REF ALT set to 0. If you can select Absolute (or Station) Pressure in the app, then just use the number on the Baro screen wherever you go. If your ballistic solver expects an altitude, use the number on the Baro screen and always input 0 as your altitude. This way your solutions will be right and you never need to adjust the Kestrel at different locations.

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