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G1 & G7 physics engine
Point-mass trajectory modelling steps the bullet through flight while accounting for gravity, drag and changing velocity.
iPhone & iPad external-ballistics calculator
Ballistic answers.
Right in your pocket.
A genuine point-mass ballistics engine with G1/G7 drag, projectile profiles, truing, wind, spin drift, Coriolis, live environmental inputs and clear down-range results.
Available now on the UK App Store.
Standalone calculations • No account required • Core data stays on your device
Built for real shooting data
From projectile data to a usable firing solution.
Configure the variables that matter, run the physics engine, and review a clear trajectory table with the corrections you need.
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Real projectile data
Choose from built-in projectile data or refresh the larger public projectile library, then save the setup in your own rifle/load profile.
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Drop & turret data
Review drop, sight correction, remaining velocity, energy and Mach number across the range increments you choose.
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Spin drift & Coriolis
Include gyroscopic spin drift and Earth-rotation effects using twist, bullet dimensions, latitude and firing direction when required.
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Live conditions
Use supported iPhone sensors for altitude, pressure, location and heading alongside temperature, humidity and wind inputs.
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Truing & elevation trim
Use real range observations to true ballistic coefficient or muzzle velocity, or apply a quick constant elevation trim when your zero has shifted.
Version 1.2
Faster to adjust. Easier to use in the field.
Version 1.2 adds flexible units and keeps the Calculate control available as you move through a long configuration screen.
✓More sequential input workflow. The setup now progresses more naturally from rifle and load basics into corrections that matter increasingly as distance grows.
✓Phone-measured inclination. Measure significant uphill or downhill shooting angles using the phone, or enter the incline manually.
✓Floating Validation and Calculate controls. Both stay available while you scroll, so checking and recalculating no longer means hunting through the setup.
✓Clear long-range progression. Wind, incline, spin drift, Coriolis and environmental inputs are grouped in a more logical order for increasing range.
✓iPhone and iPad layouts. The same setup and results workflow scales cleanly to the larger iPad display.
New in 2.2: inclination from the phone
For significantly uphill or downhill shots, the app can now use the phone as an inclinometer. Hold it flat against the top of the scope or rail, pointed with the barrel, then feed that angle directly into the ballistic solution.
App walkthrough
See Bob on Ballistics working on a real iPhone.
The Version 1.2 walkthrough shows the revised configuration flow, floating Validation data and Calculate controls, inclination measurement, environmental inputs and the long-range results display.
The application is designed as a civilian calculation and reference tool. It does not connect to or control a firearm, weapon sight or fire-control system.
One workflow
Configure. Calculate. Read the result.
The interface keeps configuration and results distinct, while the floating Calculate button makes it quicker to change a variable and rerun the trajectory.
✓Choose or enter projectile data including weight, ballistic coefficient and G1/G7 drag model.
✓Set rifle and environment inputs such as velocity, sight height, zero, wind and pressure.
✓Add advanced corrections including spin drift and Coriolis where they matter.
✓Review the range table with drop, correction, velocity, energy and Mach in one place.
VERSION 1.2 ON iPAD
Latest iPad interface
The iPad layout now shows the revised sequential configuration flow, floating Validation Data and Calculate controls, phone-assisted inclination, environmental inputs and the long-range transonic/subsonic results display.
Privacy by design
Your calculations stay yours.
The physics engine, profiles, truing and settings operate locally on your device. No account or login is required.
Local sensors
Location, altitude, heading and pressure are used locally as calculation inputs.
Location, altitude, heading and pressure are used locally as calculation inputs.
No tracking
No analytics account, advertising tracker or developer telemetry is required for core operation.
No analytics account, advertising tracker or developer telemetry is required for core operation.
Optional library refresh
The projectile-library refresh performs a user-initiated, one-way download of public projectile specifications.
The projectile-library refresh performs a user-initiated, one-way download of public projectile specifications.
Want to understand the physics?
The support page includes a downloadable plain-English guide explaining gravity, drag, G1/G7 ballistic coefficient, wind, spin drift, Coriolis, weather, truing, elevation trim and the sound barrier.