When you first run Weta Precision, you will be asked to allow access to your location. We use the OpenWeather online service to retrieve environmental information in your area, and for this to work Weta Precision requires access to your location.

We do not save your location, or use background location data.

Even if you intend to use a Bluetooth weather device, we still retrieve your location weather as a backup, so please select Allow when prompted.

Click the menu icon at the top left to open the drawer. Here you'll see various options including Rifles, Bullets and Devices.

As different countries and people prefer varying combinations of units, get started by clicking Settings and choose your preferences.

You can choose any combination of units, and many such as scope height and bullet speed can be overridden when entering details into forms.

The most important items are the weather and range units.

There's no Save option, simply select your preferred units and use the back button at top left to head back to the menu.

We've started you off with a sample rifle and bullet. You can edit their details by clicking the pencil icon to their right.

Edit the sample rifle and overtype the make and model and any other details.

I find it useful to enter my serial number here as I'm required to provide it at one of my clubs.

The rifle type (rimfire, centrefire) is purely to set a maximum slider distance in the calculator screen.

Setting the barrel twist is required if you want your spin drift calculated.

Weta Pro allows you to specify the length of your barrel and muzzle thread for reference.

You can also add any notes about your rifle, and the make and model of a muzzle brake or sound moderator.

Along with setting your zero distance, Weta Pro allows you to specify the distance from your chronograph so that your velocity can be calculated accurately.

In addition, if you record the weather conditions when you zero, differences in weather can automatically be calculated for you.

Your scope height is the distance from the centre of the barrel to the centre of the scope, measured at the middle of the scope.

To do this, measure the barrel diameter and halve it. Measure the scope diameter and halve it. Finally measure the distance between them, then add all three numbers together.

Finally, select your turret type. There's no option to select a specific scope or reticle.

Click Save, which will save your details and take you back to the menu.

The entry will update with your new details. When selected, it will be highlighted as shown above.

You can add as many rifles as you like. Just click "Add New Entry" under Rifles. Once added, they will be selected - new bullets are always added to the selected rifle.

Once you've selected your rifle, the list of Bullets will display the bullets you've added to it.

You can add multiple bullets to a rifle by clicking "Add New Entry".

Edit the sample by clicking the pencil icon, just as you did for the rifle.

Overtype the text with your own details. There are a lot of entries you can add, and they're grouped to make it easier.

If you forget to add a mandatory item, you'll be prompted when you try to save it.

Powders tend to burn faster at higher temperature - the burn rate. This increases pressure and velocity.

Weta Pro allows you to account for this when setting your velocity.

To use Powder Temp, chronograph your setup at different times of the year (i.e. at different temperatures) and enter at least two pairs in any order.

Weta Pro will then calculate the velocity of your bullet based on the current temperature.

The Metrics section contains a lot of important information about your bullet, and as with the free version, you can specify the atmospheric model and BC.

If you're using a bullet with multiple velocity based BCs, select "Multi BC" and enter the details from the bullet manufacturer, from highest to lowest velocity.

Enter as many as you need leaving the others empty. The final velocity should read 0.

Before you save, remember to select the correct drag model (G1, G7 etc) for the information you have available.

The entries under Spin Drift are required if you want spin drift to be calculated for you. You can often find the bullet head length online.

Your changes will be reflected in the Bullets card right away, but it will not be selected.

Select it and slide the drawer away to get back to the calculator.

You can add as many bullets to the rifle as you like. Just click "Add New Entry" under Bullets when you have selected a Rifle.

Your environmental conditions have enormous impact on bullet performance and trajectory.

Tap the top right location icon to see your current conditions as determined by the OpenWeather service.

min and max refer to the predicted minimum and maximum temperature in your location.

We can also fetch your what3words as Emergency Services are increasingly able to use them to locate you.

Refresh the location screen to get hold of it.

You can override the forecasted humidity and air pressure (both very important for accurate calculations) by tapping that area of the screen.

Make your changes then click Confirm to save them. Your air pressure will be set in the unit you chose in Settings:

• Inch of mercury (inHg)

• Hectopascal / Millibar (hPa)

You can fine tune the temperature to your exact location by sliding the display up and down, overriding the forecasted weather.

When overriding the temperature, the min, max and feels like will all read the same value and are not used in any calculations.

Navigate back to the calculator...

The main menu of Weta Pro has a Devices section. This stores a list of the Bluetooth devices you've added.

Click "Add new Device"

Next, power on your weather meter and it will appear in the list of nearby devices.

You do not need to "pair" your device in your phone's Bluetooth settings.

Click a device and it will be inspected for support.

Once the battery level and manufacturer details have been updated, click "Add This Device" to be taken back to the main menu.

You only need to add a device once.

Here, I've added both devices by running through the Scan sequence twice, and selected the Skywatch meter.

You can remove a device at any time by clicking the bin icon next to it.

If you have a device selected, the Device icon will be displayed above the calculator.

I've been working on a virtual Range Finder, which utilises your phone's GPS location in order to estimate the distance from your target.

This provides a very handy estimate if you don't own a laser range finder.

Click "Reset", and as you walk the estimated distance will be calculated and displayed.

The accuracy depends entirely on your GPS signal strength (better outside than indoors), phone and operating system.