GS Ballistics

The distance is changed with the gauge: the elevation updates automatically. On screen you find:

• the bullet and the optics currently active;
• the gauge and the distance set on it;
• slope angle, temperature, pressure and muzzle velocity used in the calculation — each one opens with a tap to be changed;
• the calculated elevation, in green when it has been verified on the range for that distance;
• the horizontal windage.

The V0 velocity is the bullet's speed as it leaves the barrel, that is the one measured at the muzzle (at the muzzle brake) with a chronograph: it is the starting point of the whole trajectory, so a wrong value here shifts the elevation at every distance.

Temperature and pressure set the air density and the speed of sound: using values other than the real ones produces an error that grows with distance. It is worth updating them from here before every shooting session.

Tapping "Slope angle" opens the same kind of popup as temperature and pressure. The "Use the phone's inclinometer" button reads the phone's sensor in real time — laid flat on top of the barrel or the scope, with its top end pointing at the target — and keeps updating the value until you stop it; from there it can also be corrected by hand before saving.

Saving updates the active range only if the distance set on the gauge matches an already saved target exactly; otherwise the value holds for this reading alone.

Three values are set on the optics card, each with the note the app shows underneath it:

• Angular unit — unit the elevation to apply is shown in: MOA or mrad, matching your scope.
• Elevation/Windage Click Value — what one turret click of elevation/windage is worth, in the unit chosen in settings. Examples: 1/4 MOA turret → 0.25, 1/8 MOA turret → 0.125, 0.1 mrad turret → 0.1.
• Elevation travel — if left blank, the main gauge's travel-based distance limit (in general Settings) won't apply to this optic.

There are four fields, each with the note the app shows underneath it:

• Sight-In Range — the distance the rifle is zeroed at with this scope: the elevation correction is zero at this distance.
• Line of Sight to Bore — the height of the scope's optical axis above the bore axis, measured ring-center to bore-center.
• Twist Rate (1:in) — the barrel's rifling twist rate (e.g. 1:8 = one full turn every 8 inches) — affects the bullet's in-flight stability.
• Rail + rings offset — extra elevation given by the canted rail/base and the rings, always in MOA. Added to the optic's own travel when computing the main gauge's lock.

Both values are always there. MOA and mrad are shown side by side and update each other: whatever you type into either field, the other immediately shows the same correction converted into the other unit.

It pays off above all when your spotter calls the correction in whichever unit they prefer: you enter it exactly as it was given to you and read straight away what it is worth in your own turret's unit, with no conversion in your head.

Below, the draggable ruler handles fine adjustment. At the bottom the app states how many clicks to dial and in which direction, how far the point of impact moves at that distance, and the click value of the turret it is using.

Every table in the app has its matching chart, reached with the same table/chart swap icon at the top right: the curve shows at a glance where the trajectory really starts to fall away, something a column of numbers makes far less immediate.

Comparing two bullets. From the bullet list, through a row's menu, a second bullet can be set as a comparison: from then on its curve is drawn on the same axes as the active bullet, in a different color, and the legend at the top says which curve is which.

It is the quickest way to see how two loads or two different bullets behave over the same distances — how much one drops against the other, where the curves separate and by how much — without switching the active profile or comparing two tables by hand.

On the axes: drop in centimeters vertically, distance in meters horizontally. The units follow the ones chosen in the settings.

The chart also marks two reference transonic thresholds, Mach 1.2 and Mach 0.8, recomputed on the speed of sound at the temperature set (at 15°C and 1013 hPa Mach 1 is about 340 m/s), together with the distance at which each curve crosses them. Against those thresholds the trajectory runs through three bands:

• Supersonic (above ~410 m/s) — the most predictable regime, the one you aim to still be in at the target.
• Transonic (~410–270 m/s) — drag and stability change abruptly: this is where groups tend to open up.
• Subsonic (below ~270 m/s) — predictable again, the band of ammunition designed to stay there from the muzzle onwards.

The band to avoid is the transonic one: better to pick a maximum working distance at which the bullet still arrives comfortably supersonic.

• Theme — choose dark or light theme for the whole app.
• Language — language for the app's text and menus.
• Round to click — round the computed elevation to the nearest click of your configured turret. Only available with a MOA scope.
• Limit to the optic's travel — when on and the active optic's elevation travel is set, the maximum distance selectable on the main gauge stops where the optic runs out of travel.