Android & Wear OS Setup Guide

Q: The Bluetooth icon stays grey, or no devices are found

Allow Nearby devices in Settings → Apps → OneShot → Permissions (Android 12 and later). • Turn on Bluetooth and put the device in pairing mode, then scan again. • ONESHOT only lists supported weather meters and chronographs (see Bluetooth devices).

Q: The weather didn't update by itself

It isn't automatic. Tap the location icon in the Firing screen header whenever you move position or conditions change.

01

Requirements

In short

ONESHOT Ballistics for Android is an offline ballistic calculator. You build a rifle profile, enter the distance and wind, and tap CALCULATE SOLUTION to get the elevation and windage to dial, plus a probability of hit from a 10,000-iteration Monte Carlo simulation. Live weather comes from your location when you have signal. The Wear OS app solves on the wrist using your last synced profile, even with the phone out of range.

Feature	Needs
ONESHOT app	Android phone on Android 7.0 or later
Wear OS app	Wear OS watch on Android 8.0 or later (every Wear OS 3, 4 and 5 watch, such as Galaxy Watch 4 and newer or Pixel Watch), paired to the phone
Live weather	Location permission and a data connection. Offline, OneShot uses the phone's barometer (if it has one) and your last known temperature.
Bluetooth weather meters & chronographs	The Nearby devices permission on Android 12 and later
Target analyzer & angle finder	Camera permission

02

Quick start

Allow about ten minutes, at home, before you go to the range. Tick each step off as you go; your progress is saved in this browser.

Mark step done

Install ONESHOT from Google Play

Install ONESHOT Ballistics from Google Play on your phone.

For the watch, open Google Play on the watch itself, search for OneShot Ballistics and tap Install.
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Accept the EULA and allow permissions

On first launch, read and accept the licence agreement (tap Wissel na Afrikaans to read it in Afrikaans), then tap I ACKNOWLEDGE AND AGREE. Allow Camera and Location when Android asks.

If you declined location, turn it on later in Settings → Apps → OneShot → Permissions → Location. The app can't ask you again by itself.
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Choose a unit system and your first rifle

The setup wizard asks for a unit preset (METRIC (MIL/m), IMPERIAL (MOA/yd) or F-CLASS (MOA/m)), then your rifle: name, caliber, muzzle velocity, zero, twist and sight height. For ammunition, pick from the bullet library, the factory loads, or type custom parameters (weight, BC with a G1 or G7 drag model, length).
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Check your units in Settings

Tap the gear icon on the Firing screen and confirm each unit under Unit System: distance, muzzle velocity, wind speed, bullet weight, sight height and Turret / Reticle Units. Pressure and temperature are under Environment.

Each rifle remembers its own distance, velocity and turret units. Selecting a rifle applies its units to the whole app, so check Settings once after first setup and whenever you add a rifle.
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Complete your equipment profile

On the Firing screen, tap MANAGE in the Equipment card. Tap + for the five-step NEW EQUIPMENT SETUP wizard (rifle, ammunition, calibration, optics & reticle, summary), or edit the active setup to add twist direction, reticle and powder sensitivity. Tap a profile under SAVED PROFILES to make it active.
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Allow Nearby devices (Bluetooth kit only)

If you use a Bluetooth weather meter or chronograph, go to Settings → Apps → OneShot → Permissions → Nearby devices and tap Allow. On Android 12 and later, scanning doesn't work without it, and the app doesn't prompt for it.
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Sync your watch

With your profile selected on the phone, open ONESHOT on the watch. The footer should show your rifle's name. If it says NO PROFILE - SOLVING ON DEFAULTS, keep both apps open for a few seconds with Bluetooth on.

The profile, units and conditions are stored on the watch, so it keeps solving later without the phone.
Mark step done

Test it at home

On the Firing screen, tap the location icon to fetch weather, enter a distance of 300, and tap CALCULATE SOLUTION. You should see elevation, windage and a probability of hit.

0 of 8 steps done ·

03

Permissions & settings

Solving never needs a permission. Each one below unlocks a feature. All of them live under Settings → Apps → OneShot → Permissions on the phone.

Phone

Location

Allow Location (precise is best)
Keep device location switched on
Used for live temperature, pressure, humidity, wind, latitude and altitude

Phone · Android 12+

Nearby devices

Allow Nearby devices
Turn on Bluetooth
Needed to find weather meters and chronographs

Phone

Camera

Allow Camera
Used by the Target Analyzer and the camera Angle Finder

Weather updates when you ask for it

ONESHOT fetches weather only when you tap the location icon in the Firing screen header ("Fetch Weather Data"). Tap it when you arrive at your position, and again if conditions change.

04

The Firing screen: from setup to solution

The Firing screen is home. Work down it from top to bottom. A typical shot goes like this:

1

You Tap SELECT RIFLE and SELECT BULLET in the Equipment card.

CALCULATE SOLUTION stays disabled until both are selected.
2

You Tap the location icon in the header.

App Fills temperature, pressure, humidity, latitude and a base wind from live weather.
3

You Enter the Distance and set the Look Angle.

For the angle, tap the capture icon while holding the phone along the line of sight, or use the camera button to open the Angle Finder. Use the m | yd chip to switch distance units.
4

You Check the wind zones and tap CALCULATE SOLUTION.

App Shows ELEVATION and WINDAGE in your turret unit, with velocity, energy and time of flight at the target, and the probability of hit.

ELEVATION / WINDAGE

ELEV4.8

WIND0.3

VELOCITY592 m/s

ENERGY1,915 J

TOF0.73 s

CALCULATE SOLUTION

POH ANALYSIS

87%

V-SD6.1 cm

H-SD8.4 cm

Illustration

Environmental card

Expand ENVIRONMENTAL to see temperature, pressure, density altitude, humidity, latitude and target direction. Use Temp Override if the temperature has changed since the last fetch, and Direction Override (or the compass toggle) to set the direction you're firing. Turn on DA MODE to shoot from a known density altitude instead of live readings.

05

Wind zones & probability of hit

Wind zones

Tap + in the WIND card to add a zone. Each zone has a Speed and an Angle (°). Tap − to remove one.
Fetching weather creates a base zone from the forecast, which is measured 10 m above the ground. Wind at your position is usually lighter and gustier, so correct the zone to what you see.
No wind zones defined means the solution has no wind in it.
Before you dial, check that the windage direction matches the wind you're reading on the flags or mirage.

Probability of hit (POH)

After every solve, ONESHOT runs 10,000 simulated shots, varying muzzle velocity, wind and your own precision, and counts how many land on the target. The POH ANALYSIS card shows the percentage, plus the vertical and horizontal spread (V-SD and H-SD) in centimetres.

Uncertainty (SD)	Default	What it models
Muzzle velocity SD	3 m/s	Shot-to-shot velocity spread from your chronograph
Wind SD	1 m/s	How far off your wind call might be
Precision	1 MOA	Your rifle-and-shooter group size
Target width × height	45 × 45 cm	The size of what you need to hit

Open UNCERTAINTIES (SD) in the POH card to change these. The result updates immediately. The values reset to the defaults when the app restarts.

06

Tools

The buttons at the bottom of the Firing screen open these tools.

RANGE CARD

DOPE table

A table of elevation and windage for a range of distances. Open its settings to choose START, END and STEP, and which columns to show: elevation and wind in MIL or MOA, velocity, energy and time of flight.

TRUING

Match real impacts

Pick a profile, then TUNE BY SPEED (muzzle velocity) or TUNE BY BC. Enter the distance and the real elevation you needed, with the conditions at the time (tap LIVE to fill them). Tap CALCULATE, then SAVE CHANGES to update the profile.

TARGET ANALYZER

Measure your groups

Take a photo or pick one from the gallery. Calibrate the scale with a reference object (A4 paper, a credit card, or an R5, R2 or R1 coin), align the corners, and tap each impact. You get extreme spread and mean radius in MOA and MIL, and can save the marked-up image.

RETICLE

See the hold

Shows your reticle with the hold and a target silhouette (IPSC, gongs or custom). Set focal plane, magnification range and click value under scope settings. Adjust DIALED ELEV and the magnification slider to match your scope.

MPBR

Maximum point-blank range

In the equipment editor, open MAX POINT BLANK RANGE (MPBR) to find the zero that keeps the bullet inside your vital zone for the longest distance, or check a specific zero.

SETTINGS

Calculations & display

Under Calculations, turn Coriolis and Spin Drift on or off. Under display, use Tactical Red Night Mode to protect your night vision, and Apparent Reticle Scale to size the reticle view.

07

Bluetooth weather meters & chronographs

Connect a device

Allow Nearby devices and turn on Bluetooth
Put the device in Bluetooth / pairing mode
Tap the Bluetooth icon in the Firing screen header to open DEVICE MANAGER
Tap the refresh (Scan) icon. Scanning runs for 30 seconds
Tap your device in the list to connect

What ONESHOT looks for

Weather meters: Kestrel (including DROP), WeatherFlow, SkyWatch, Calypso
Chronographs: Garmin Xero, LabRadar and other devices with "chrono" in the name

Readings are used in the equipment editor. A weather meter updates temperature, pressure and humidity, and a chronograph fills in muzzle velocity.

08

Wear OS watch

The watch is a complete solver on your wrist. It follows the phone while the phone is nearby, and always works out the solution on the watch itself, so it keeps working with the phone in the vehicle, out of range, or flat.

ONESHOT

RANGE550m

ANGLE3°

ELEVATION4.80mil

WINDAGE→0.30mil

WIND3.5m/s3 O CLOCK

TEMP18°C

DOPE 308 Win 168gr 2650fps

Illustration

Reading the screen

RANGE · ANGLE: Target distance and inclination in degrees.
ELEVATION · WINDAGE: What to dial. The arrow shows which way to hold for wind.
WIND · TEMP: Wind speed with its clock direction, and air temperature from the phone. STD means standard atmosphere until the phone sends real conditions.
Footer: The rifle, bullet weight and muzzle velocity the solution is for.

Controls

Do this	To
Tap RANGE, ANGLE or WIND	Choose which value the crown changes. The selected cell glows gold.
Turn the crown or rotating bezel	Adjust the selected value: range by 10 m, angle by 1° and wind by 0.5 m/s per click, with a haptic tick each step.
Long-press RANGE, ANGLE or WIND	Type or dictate an exact value. Enter just the number, such as 500; anything else is ignored.
Swipe right	Go back.

Limits: range 0–2,000 m, wind 0–50 m/s, angle ±90°. Wind direction is set on the phone.

Phone nearby, or not

Phone nearby

The phone sends the active profile, units, conditions and shot inputs to the watch. When you stop turning the crown, the watch sends the new value back so the phone matches.

Standalone

With no phone, the watch keeps solving with the last profile and conditions it received. Probability of hit is calculated on the phone only.

Never dial "NO PROFILE" numbers

If the footer shows NO PROFILE - SOLVING ON DEFAULTS, the watch hasn't received your rifle yet and is solving for a generic bullet. Open ONESHOT on the phone with your profile selected, then open it on the watch.

09

How ONESHOT solves

Four things go into every solution. Getting each one right is what makes the number worth dialing.

01 · Profiles

Isolated rifle profiles

Each profile stores its own rifle, twist, sight height, zero, bullet and velocity in a local database on your phone, so data from one rifle never leaks into another.

02 · Units & drag

Units and ballistic coefficient

Each rifle keeps its own distance, velocity and turret units: one in m/s and MIL, another in fps and MOA. Bullets use a G1 or G7 drag model, with velocity-banded BCs where the bullet data includes them.

03 · Atmosphere

Density altitude

Temperature, pressure and humidity set the air density the bullet flies through. Live weather supplies them; offline, the phone's barometer and your last reading fill in. How density altitude is calculated.

04 · Monte Carlo

Probability of hit

10,000 simulated shots with realistic velocity, wind and shooter spread turn a single aim point into a hit probability. The statistical model · Coriolis & Eötvös effects.

10

What the app says, and what to do

When something is missing, ONESHOT tells you. Here is each message and the fix.

Message	Where	What to do
Location unavailable. Cannot fetch weather.	Phone	Turn on device location and allow the Location permission. Step outside for a GPS fix, then tap the location icon again.
LOCATION PERMISSION REQUIRED	Phone	Turn on location in Settings → Apps → OneShot → Permissions. Without it, enter conditions yourself or use DA MODE.
Offline: pressure from the barometer, temperature is last known.	Phone	No signal. Pressure is measured live; temperature is your last reading. Use Temp Override if it has changed.
Offline: no barometer, using last known pressure.	Phone	Your phone has no barometer. If you know the density altitude, turn on DA MODE.
Weather service unavailable and no sensors to fall back on.	Phone	No weather and no barometer. Use DA MODE and Temp Override.
Unexpected error during weather update.	Phone	Tap the location icon again in a moment.
Please fix errors before saving · Required · Must be > 0	Phone	A field in the equipment editor is empty or zero. Fill in the highlighted fields.
Step size must be greater than 0.	Phone	In the range card settings, set STEP above zero.
Invalid Corners	Phone	In the target analyzer, tap the four corners of the reference again.
NO PROFILE - SOLVING ON DEFAULTS	Watch	Don't use these numbers. Sync from the phone (see Wear OS watch).
STD (temperature)	Watch	The watch hasn't received conditions yet. Fetch weather on the phone with the watch app open.

11

Troubleshooting

CALCULATE SOLUTION is greyed out, or no solution appears

Select both a rifle and a bullet in the Equipment card. The distance, muzzle velocity and zero distance must all be greater than zero.

My units changed after I selected a rifle

Each rifle remembers its own distance, velocity and turret units, and applies them when you select it. Set the units you want in Settings with that rifle active, or use the m | yd chip on the Firing screen, which saves to the rifle.

The Bluetooth icon stays grey, or no devices are found

Allow Nearby devices in Settings → Apps → OneShot → Permissions (Android 12 and later).
Turn on Bluetooth and put the device in pairing mode, then scan again.
ONESHOT only lists supported weather meters and chronographs (see Bluetooth devices).

Can my rangefinder send the distance to ONESHOT?

Not yet. Type the distance into the Firing screen, or set it with the crown on the watch.

The weather didn't update by itself

It isn't automatic. Tap the location icon in the Firing screen header whenever you move position or conditions change.

The watch shows NO PROFILE or doesn't update

Make sure the watch is paired to the phone (through the Galaxy Wearable or Pixel Watch app) with Bluetooth on. Select your profile on the phone, then open ONESHOT on the watch. The watch picks up changes while its app is open.

The watch and phone show slightly different numbers

The watch works out its own solution from the last profile and conditions it received. If conditions have changed since then, or you've changed Coriolis or spin-drift settings, expect small differences. Open the watch app with the phone nearby to refresh it.

Can I use voice commands on Android?

Not on the phone yet. On the watch, long-press RANGE, ANGLE or WIND and dictate a number. Hands-free Siri commands are coming with the iPhone and Apple Watch app.

Is the app available in Afrikaans?

The app itself is in English. You can read the licence agreement in Afrikaans, and this guide is available in Afrikaans.

Does ONESHOT need signal?

No. Every solution is calculated on the phone or watch. Signal is only used to fetch live weather for your location.

Still stuck?

Read the technical articles on how the solver works, see the iPhone & Apple Watch guide, or get in touch.