advertisement
SNIPER CALCULATOR
Ballistic Calculator
User's Guide
Index
Contents
Introduction
Purpose
External Ballistic Calculator is aimed towards recreational long range shooters, Army Snipers and Law
Enforcement Officers. It helps shooters calculate hold overs, and scope settings necessary for long range shots. It also keep log of shots fired, in order to make Data On Previous Engagements (DOPE) available for a later review. Software is designed to operate on an Android platform in portrait orientation only.
Concept of operation
External ballistics is the part of the science of ballistics that deals with the behavior of a non-powered projectile in flight. External ballistics deals with the behavior of the bullet after it exits the barrel and before it hits the target, so it lies between transitional ballistics and terminal ballistics.
Features
Multiple drag calculation functions
Several drag curve models optimized for several standard projectile shapes are available. The resulting fixed drag curve models for several standard projectile shapes or types are supported:
G1 or Ingalls (by far the most popular) tandard model, flat-based pointed bullet, 3.28 calibers in length, with a 1.32 caliber length nose, with a 2 caliber (blunt) nose ogive.
G2 (Aberdeen J projectile) Special model for a long conical-point banded artillery projectile,
5.19 calibers long with a .5 caliber 6° boat tail. Not generally applicable to small arms.
G5 (short 7.5° boat-tail, 6.19 calibers long tangent ogive) For Moderate (low base) boat tails,
4.29 calibers long with a .49 caliber 7° 30′ boat tail and a 2.1 caliber nose with a 6.19 caliber tangent nose ogive.
G6 (flat base, 6 calibers long secant ogive) For flat-based spire-point type bullets, 4.81 calibers long and a 2.53 caliber nose with a 6.99 caliber secant nose ogive.
G7 ((long 7.5° boat-tail, 10 calibers tangent ogive, preferred by some manufacturers for verylow-drag bullets) For VLD type, or pointed boat tails, 4.23 calibers long with with a .6 caliber long 7° 30′ Tail Taper and a 2.18 caliber long nose with a 10 caliber tangent nose ogive. Most modern US military boat tailed bullets match this model.
External factors
Wind (Wind has a range of effects, the first being the effect of making the bullet deviate to the side.)
Vertical angels (The vertical angle (or elevation) of a shot will also affect the trajectory of the shot. Ballistic tables for small caliber projectiles (fired from pistols or rifles) assume that gravity is acting nearly perpendicular to the bullet path. If the angle is up or down, then the perpendicular acceleration will actually be less.)
Distance
Ambient air density (Air temperature, pressure, and humidity variations make up the ambient air density. Humidity has a counter intuitive impact. Since water vapor has a density of 0.8 grams per liter, while dry air averages about 1.225 grams per liter, higher humidity actually decreases the air density, and therefore decreases the drag.)
Spin drift (PRO version only) (Even in completely calm air, with no sideways air movement at all, a spin-stabilized projectile will experience a spin-induced sideways component. For a right hand (clockwise) direction of rotation this component will always be to the right. For a left hand (counterclockwise) direction of rotation this component will always be to the left.)
Coriolis drift (PRO version only) (Coriolis drift is caused by the Coriolis effect and the Eötvös effect. These effects cause drift related to the spin of the Earth, known as Coriolis drift.
Coriolis drift can be up, down, left or right. Coriolis drift is not an aerodynamic effect; it is a consequence of flying from one point to another across the surface of a rotating Earth.
The direction of Coriolis drift depends on the firer's and target's location or latitude on the planet Earth, and the azimuth of firing. The magnitude of the drift depends on the firing and target location, azimuth, and time of flight.)
A lot of good info is available in “A Short Course in External Ballistics” by Fr. Frog.
(www.throwinglead.com)
Functionality
Sniper Calculator is designed with the usability in mind from the ground up. All tasks performed often, and while shooting are accessible from a single screen (CALC). Of course, there is always a certain workflow to follow. Before using a Calculator you need to enter your weapon and ammunition data first.
Application screen is divided into 5 TABs: Calculations (CALC), Environment (ENV), Weapon and
Ammo (WPN) and Logbook (LOG). Additional functionality and settings are available by pressing
Android device OPTIONS button.
OPTIONS Menu is content sensitive, and will give you different options, depending on which TAB you press the Android OPTIONS button.
QUICK START
1. Select “WPN” tab, press Android OPTIONS button, and select “Add Weapon” or “Add
Ammunition”
2. Select “ENV” tab, and enter general weather data
3. Select “CALC” tab, enter range, wind speed, direction
4. Shoot
5. Log your shot, and switch to “LOG” tab
CALC - Calculations Screen
This is a main screen, used most of the time. Solution is automatically recalculated every time, data is changed. If Kestrel weather station is used, parameters from Kestrel will be automatically transferred to Calculator when pushing “SET” button on the Kestrel panel.
Push/Hold to
Decrease Range
Push to
Enter Range
Push/Hold to
Increase Range
Push to access
OPTIONS
Drag to
Mark Impact
Drag to set
Wind Direction
Push to
Increase Slope
Push to
Enter Slope
Push to
Decrease Slope
Push to
Set shooting direction
Push to
Increase
Windspeed
Push to
Enter
Windspeed
Push to
Decrease
Windspeed
Push to
Log hit
Push/Hold to
Decrease Zoom
Push to
Switch Zoom
Push/Hold to
Increase Zoom
Calculations screen integrates most common controls, with most commonly used tools. Range, Slope,
Wind Speed, Wind Direction, Cardinal direction of shooting, and Scope magnification can be changed directly. Values can be altered by using red arrow keys, or by entering value directly by pressing on
the red text labels. Wind Direction is a 360 deg. Slider, around the scope view.
1. Pressing red arrow keys: Values will change in increments/decrements of 1.
2. Holding red arrow keys: Values will start to change in small steps by 1, then will gradually switch to larger increments/decrements by 10.
3. Pressing a red label between the arrows: will give you a direct entry panel.
Values used for calculation are displayed top left and top right in white color. Every time, a parameter is changed, Calculator will recalculate a solution, and display the results in yellow color on the screen:
Elevation: Number of clicks on top scope turret
Windage:
Mil dot:
Number of clicks on side windage turret
Size of 1 mil dot at a given distance and scope magnification
Impact point: Yellow dot in scope view
Gray impact (actual) point can be moved around to mark actual impact point after each shot. This is the impact point logged by pressing red LOG button in a bottom right corner of the screen.
When shooting long range, don’t forget to set the cardinal direction of shooting in the lower left corner.
Using the Range Calculator
Range calculator will popup when pressing “RANGE” button on top center of the screen. This panel gives user a few options:
To enter RANGE to target directly, by selecting “Range ()” input field, and keying in the distance.
To calculate RANGE, by entering a number of Mils, that an object of a known size will cover in the scope reticule, and then pressing “Calculate Range Button” or “Set” button directly.
Using the Solution Table
You have an option to list a solution table with all the data available, for a given distance. Solution
Table is available in OPTION menu at the CALC TAB.
1. Select “SETTINGS” and set the columns you want in a solution Table, Min/Max range, and a distance step.
2. Select “SOLUTION TABLE” from the OPTION menu, to display the solution table. You can pan the table up and down, and left and right to display all values in the table. Line marked in
RED, is the maximum distance, where bullet is still supersonic.
Using Truing correction
Often, theoretical data about the ammunition or weapon system is not 100% correct. Truing enables users to adjust muzzle velocity based on a difference between actual and calculated impact point on a known distance.
Double check if weapon and ammunition data is correct.
Enter known distance to target, and set your windage and elevation.
Shoot, and measure the distance between the bulls eye and actual hole in the target
Access Truing, via OPTIONS menu on CALC TAB, and enter the distance in the “Truing()” Field.
Press “Calculate Adjustment” to calculate the difference in muzzle velocity. Press “Set” to save this to the Ammunition parameters.
Using Kestrel Weather Station
Sniper Calculator can use weather data provided by the Kestrel weather station over the Bluetooth connection.
Make sure your Kestrel device is calibrated and working correctly. It is also a good idea to use the same system (metric /imperial) on Kestrel and Sniper
Calculator.
Pair the Kestrel with the Android device using BT connectivity options.
Access Kestrel application screen in Calculator by selection “OPTIONS -> Kestrel” in ENV or CALC tab.
If Kestrel is connected top line will show “CONNECTED
TO…” string, and data will update according to the
Kestrel settings.
Set shooting direction by dragging the red arrow
Data coming from the Kestrel device is shown in yellow, and relative (calculated) wind direction is displayed in the middle of the compass screen. “Shoot” marks the shooting direction and “Wind” marks the actual wind direction.
Press “Set” to use the data in the calculation.
Kestrel related settings are available under “OPTIONS -> Settings -> Kestrel” menu:
Data from Kestrel: Select parameters to read from a Kestrel device
Units: Select which settings (metric/imperial) have priority – Kestrel or Sniper Calculator
Refresh Rate: Rate of data update from Kestrel device.
If Kestrel did not connect automatically you can initiate pairing by pressing on the top line of the screen.
ENV - Environmental data
Data which changes less frequently (like weather) is entered on this screen. Weather data is organized into three expandable sections. Sections can be expanded or collapsed by pressing a red arrow (or triangle) on the right side of the screen. Kestrel device data is available through an OPTION button.
Location
Geographic location. This is a rough geo location data. It is needed for Coriolis drift calculations only. Enter it manually or select “GPS location” to use device’s built in
GPS receiver. (if GPS signal is available, last update time will be displayed)
Weather
Temperature, Air Pressure and Humidity are used in ballistic calculations.
If Air pressure is unknown, altitude above sea level can be used in a pinch by ticking
“STD. PRESSUARE AT ALT” check box.
Wind
Wind speed and direction can be entered here, or in the CALC TAB.
Kestrel
Kestrel screen is available by selecting “Kestrel” from an OPTIONS menu. Kestrel related settings are available under “Settings -> Kestrel”.
Yellow arrow displays Kestrel compass data (absolute wind direction). Mark shooting direction by dragging red arrow in the compass. Calculator will then calculate relative wind direction, to be used in the calculation. Pres “Set” to use current data displayed.
WPN - Weapon and Ammo data
Before using ballistic calculator, weapon type and ammo type must be defined. User can define more weapons and different ammo to be used later on. Data is organized into two expandable sections.
Sections can be expanded or collapsed by pressing a red arrow (or triangle) on the right side of the screen.
Expand Weapon or Ammunition data by pressing on a Weapon or Ammunition name.
1. To ADD new weapon or ammunition type press Android OPTIONS button and select “Add
Firearm” or “Add Ammunition”.
2. To change the Firearm (weapon) type, Expand the Firearm dropdown, and select (click) the firearm name in yellow color. Selection Pop Up with all available Firearms in the database will open.
3. To change the Ammunition type, Expand the Ammunition dropdown, and select (click) the
Ammunition name in yellow color. Selection Pop Up with all available Ammunition in the database will open.
HINT:
Firearm and Ammunition data is often available as a mix of metric and imperial quantities. A lot of units can be set individually in the Settings menu of the Sniper Calculator, but it is hard to guess the right combination. In such cases we suggest to go to settings and select general imperial units first, enter all the parameters provided as metric units, then select general imperial units in the setting, and add all the parameters provided in the imperial units.
Firearm Data
Weapon Name: You can change currently selected weapon, by pressing a yellow
weapon name label.
Zero Range: Range at which weapon is currently zeroed.
Sight height: height if scope center over bore center.
Sight offset: left or right optics offset
Max zoom: Maximum zoom available on a scope mounted
Reticle Type: Select Scope Reticule
Click Type: Type of units used by current scope
Elevation Click Value: Value of 1 click on a scope elevation turret
Windage Click Value: Value of 1 click on a scope windage turret
Optional:
Barrel Length, Barrel Twist, Twist direction
Ammunition Data
Ammunition name: You can change currently selected Ammunition, by pressing a
yellow Ammo name label.
Weight: Weight of bullet
Velocity: V0 – muzzle velocity
Ballistic coefficient: BC of a bullet
Drag Function: Drag function, for selected bullet shape
Optional:
Diameter (bullet), Length (bullet), Powder temperature when data recorded
To DELETE current weapon or ammunition type press Android OPTIONS button and select:
DELETE FIREARM to delete currently selected firearm
DELETE AMMUNITION to delete currently selected ammunition
LOG - Log Book
Shots fired can be logged, by marking bullet hit position in CALC screen. ALL shot data is logged, and can be displayed in LOG screen in form of a shooter logbook.
Logs can be exported via Android OPTIONS menu. Export format choice is CSV (comma separated values) for further processing, or HTML format for immediate printing.
Options menu
Additional functionality and options are accessible via Android device OPTIONS button.
SOLUTION TABLE: Display solution table for current Weapon and Ammunition
TRUING: Actual vs. Calculated impact point correction
KESTREL: Access weather data from a Kestrel Weather Station
SETTINGS: Application Settings
HELP: This help document
EXIT: Exit program
Additional Options on WPN tab:
ADD FIREARM: Add new firearm to the application
ADD AMMUNITION: Add new ammunition type to the application
EXPORT FIREARM: Export firearm data as a message (gmail) o Users can export all firearms or a single (selected) firearm from calculator o Users can send data to other users o To import the received data, open a message attachment, (select sniper calc)
EXPORT AMMUNITION: Export ammunition data as a message (gmail) o Users can export all ammunition data or a single (selected) ammo type from calculator o Users can send data to other users o To import the received data, open a message attachment, (select sniper calc)
DELETE FIREARM: Delete currently selected firearm
DELETE AMMUNITION: Delete currently selected ammunition
Additional Options on LOG tab:
DELETE LOGS: Clear all logs
EXPORT LOGS: Export logs from the application
Solution table Export is available by pressing OPTIONS button, while on solution table view.
Settings
Behavior and look and feel of Bal Calc is controlled by the pre-set defaults that can be changed from the settings menu. Settings menu in Ballistic Calc:
SETTINGS: Program settings o Units: Select units used by the calculator
Measurement units (Metric / Imperial)
Wind speed units (km/h – m/s)
Pressure units (mmHg / inHg / Pa / hPa / mBar)
Bullet weight unit (Grain / Gram)
Windage and Elevation units (Click / MOA-MRAD) o Calculation
Spin Drift
Coriolis
Atmosphere o Solution Table
Columns
Maximum Range
Minimum Range
Step size o Logs
Group Logs by... o Kestrel
Data Used
Units
Refresh Rate o Display
Keep device screen on
advertisement
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Related manuals
advertisement