If you used JBM
For years JBM was the calculator people checked everything else against. In August 2026 the web calculators went offline, and the site now says its author has retired them and points to the iPhone apps he has written. That’s fair enough after that long — but if your phone is an Android, it leaves you without the tool you trusted.
Being straight up front. JBM was a web calculator: you could run it on any computer, and it had a very large bullet library and a whole shelf of specialist tools. Harson Ballistics is an Android app, with no web version and no iPhone version. Its library is 234 bullets and 48 factory loads, each with the source it came from — smaller than JBM’s, and you can add any bullet yourself from the figures on the box.
It runs on the phone, with no signal. Set up the rifle, scope and load once and every solution after that is calculated on the device. No account, nothing to log into at the far end of a paddock.
The same kind of maths. Point-mass trajectory with G1 and G7 drag, velocity-banded ballistic coefficients where the bullet maker publishes them, air density from real temperature, pressure and humidity, Miller stability from your twist, spin drift and Coriolis. Every result is cross-checked against an independent reference solver before a release.
Your reticle, not a table. Drop and wind come out in MRAD, MOA, clicks, centimetres and inches at once, and the hold is drawn on the reticle you are actually looking through, scaled to magnification. Reticles are drawn from the makers’ own spec sheets, and every verified one is published here so you can check yours before installing.
A range card you can print for the scope cap, and truing from what you actually saw on target.
The solver, the full bullet and factory-load library, your own custom bullets, generic Mil-Dot and MOA reticles, two rifle profiles and truing are free, for good. No ads. Pro adds the manufacturer reticle library and unlimited rifles, at the price shown in your own currency on Google Play.
Also coming from Strelok? Read this one →
Harson.ai is not affiliated with JBM Ballistics; the name is used only to describe what shooters are searching for. Harson Ballistics is a calculation aid, not a substitute for your own judgement, safe firearm handling, or confirming your zero on a range.
