Gordon's Reloading Tool was the free desktop simulator a lot of reloaders grew up on, and it was good. Its author, known as rgf, died in 2022. Development had continued in the community's hands for a while, but in July 2026 the grtools.de site posted that downloads were removed and bugs would no longer be fixed. Copies still circulate and still run. If you have one that works, it remains a legitimate tool.
IBC keeps the useful core of what GRT offered: a free way to simulate loads before you load them. It runs in your browser instead of a desktop install, on Windows, Linux, Mac, or a phone at the bench.
The calculator covers 607 rifle and pistol cartridges with 5,671 bullets, and its powder catalog lists only powders we have measured against published loads. Enter a load from your reloading manual and it predicts velocity and peak pressure, draws the pressure and velocity curves, and rates every load against the cartridge's pressure ceiling. There is a charge work-up ladder with a verdict per rung, trajectory and drop tables, a load logbook, and a printable range checklist for the ladder.
Accuracy is published, not implied. IBC runs its engine against a corpus of thousands of loads from printed reloading manuals and publishes the error rates, overall and broken out per powder and per cartridge, with the method and provenance alongside. Neither GRT nor any other simulator we know of publishes comparable numbers, so if you are coming from GRT you never had a way to judge how much to trust it. Now you do.
Honestly: chronograph imports from MagnetoSpeed, Caldwell, ProChrono, and LabRadar; the OBT tool; cartridge and wildcat design; report printing; and GRT's much larger community-fed powder set. IBC prints the work-up checklist and saves loads to a logbook, but if your workflow depends on chrono calibration or wildcat design specifically, an archived GRT copy may still be the better answer for you.
IBC's free tier covers full single-load predictions, trajectory, and the first steps of the work-up ladder; PRO ($17.99/month) unlocks the whole ladder and the charts. No install, no disc, no account needed to try it.
IBC is a comparison tool, not a load table. It does not publish loads: start from a load in a current reloading manual, enter it, and compare. Start 10% below the maximum charge and work up. The GRT facts on this page come from the grtools.de site's own notices.