COLDBORE by AK Systems

Setup

Conditions

Pressure must be the absolute reading where you stand, not the sea-level figure a weather app shows. Fetching by location converts it for you using the altitude above.

Density altitude —

Target

3 o’clock wind blowing from
Elevation —
Windage —
Velocity —
Energy —
Stability — Supersonic to — Max ordinate — Spin drift —
Range Elev Clicks Wind Vel Mach Energy TOF s

DOPE card

Atmosphere comes from the Solver tab; the card is always computed for level ground so it stays valid whatever you are shooting at. The wind column is pure wind deflection at the reference speed, so you can halve it for a half-value wind — spin drift is listed separately because it is always there and never scales with the wind.

Turret label

A strip printed at true size, cut out and wrapped round the turret, so a range is dialled straight off the scope. It is built from the same solution as the card, in the conditions on the Solver tab.

Travel per turn is on your scope or in its manual — 10 MRAD and 15 MOA are common. Measure the turret with calipers; the defaults are a typical 32 × 18 mm. Rotation direction only decides which way the numbers run: if the preview ring disagrees with your scope, switch it. The index mark is the fixed line you read the turret against — engraved on the housing at the base on most scopes, which is where the graduations go.

Distances

Preview shown at true size

Handload simulation Estimate

This models the burn inside the case to show how a charge behaves — velocity, how hard pressure climbs, how full the case is. It is not load data. Start from a published start charge, work up watching for pressure signs, and cross-check every result against a current reloading manual. Calibrating to your own chronograph makes the comparison between charges trustworthy; the absolute pressure figure never becomes exact.

Cartridge

Bullet

The seated part of the bullet takes volume out of the case; a boat tail takes less than a cylinder. Worth ~5 m/s on a 6.5 mm match bullet.

Powder

Calibration

Enter one charge you have actually chronographed. The model then matches your rifle instead of a generic one.

Muzzle velocity —
Peak pressure —
Case fill —
Powder burnt —
Peak pressure against the CIP ceiling —

Charge ladder

Charge gr Grams MV Peak bar % max Fill Burnt

Load book

Your record of what you actually loaded and what it did. Saved loads keep the whole recipe — brass, primer, charge, seating — plus what the chronograph and the target showed. They travel with your backup file.

Writes the predicted muzzle velocity onto a load the solver and DOPE cards can use.

Rifles

Ammunition

Backup & transfer

All data lives on this device. Export a backup file to move your rifles, loads, settings and device mappings to another phone or computer — share it (AirDrop, message, drive) and import it there.

Device link Coming soon

Direct Bluetooth connection to Kestrel weather meters and to the Garmin Xero C1/C2 and Athlon Rangecraft chronographs is in development — live conditions will fill in the solver, and shot strings will land in the Loads tab where a chronographed ladder is exactly what fits a powder.

Until then: enter conditions manually on the Solver tab, and set your chronographed average MV on the load in the Library.

Rifle

Tall-target test: dial a known amount up a plumb line and measure what the impact actually moved. Dial 5.00 mil, get 4.85, enter 0.970. Do this before truing velocity — otherwise a tracking error hides inside a false muzzle velocity.

Ammunition

Powder sensitivity: how much MV rises per degree above reference temperature. Leave 0 to ignore.

Notice

Coldbore Ballistics

A ballistic solver, handload workbench and DOPE card printer that runs entirely on your own device.

Version · © 2026 AK Systems. All rights reserved.

Your data

Rifles, loads, powders and your load book are stored on this device only. Nothing is uploaded and there is no account. The single exception is fetching conditions by location, which sends your coordinates to Open-Meteo when you press that button. Use Library → Backup to move everything to another device.

Where the numbers come from

Safety

Firing solutions and simulated pressures are estimates, not guarantees. Verify zero and dope with live fire. Interior ballistics output is not load data: start from a published start charge, work up watching for pressure signs, and cross-check every result against a current reloading manual. You are responsible for what you load and what you shoot at.

True to your dope

Enter what you actually had to dial to hit at each range, in calm conditions. Coldbore bends the solution to match: muzzle velocity from a mid-range impact, drag from a far one near transonic. Do the tall-target test first — a scope that tracks 3% off will otherwise hide inside a wrong velocity.

Range Dialled MRAD

Cartridge

Case capacity is the water weight of a fired, sized case with the primer in — the figure that varies most between brands, so measure yours. Maximum pressure is the CIP or SAAMI ceiling for the cartridge.

Propellant model

Vivacity is the one that moves velocity — raise it and the powder burns faster. Bulk density only affects the case-fill figure, but that is the number that tells you whether the charge physically fits.

Save load

Fit a powder from chronograph data

Fire a charge ladder and enter what your chronograph measured. Coldbore solves for the burn parameters that reproduce those velocities — giving you a model of that powder in your barrel, with your brass and lot. Two points work; four or more also pin down how steeply pressure builds.

Your own chronograph: your barrel. Manual data: the maker's test barrel — Vihtavuori publish 650 mm for most rifle cartridges, Hodgdon and Hornady usually 24″ (610 mm). Getting this wrong shifts every later prediction.

Charge grMeasured MV
Takes a few seconds.

Map characteristic

Latest packet, parsed with these settings:

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