CaliberAtlas › Methodology
CaliberAtlas combines published reference data, stored catalog entries, and calculated results. Evidence coverage varies by record.
See reviewed products and remaining source gaps.
Last updated: September 11, 2026
A claim of physical measurement needs an identified measurer, method, and conditions. We do not claim that CaliberAtlas has independently field-tested every load or BC. See the reference comparisons for the scope of our numerical checks.
We prioritize published, authoritative sources and identify unresolved evidence in the source notes. Some older catalog entries still have incomplete supporting documentation. A stored value should not be read as an independently verified measurement.
G1 and G7 describe different reference drag models. Published BCs can vary with velocity; a BC number alone does not identify its measurement method or conditions.
Complete source receipts identify the publisher, document, review date, and supporting passage, and distinguish exact-product evidence from evidence for a broader bullet class or product line. A source review does not independently measure a BC. Unstated velocity intervals, methods, and conditions remain unknown. Multiple published BCs need their stated velocity conditions and reference model preserved, rather than being described as universal values for particular distances.
Hornady's explanation of BC and velocity
Pressure values are shown as catalog values unless CaliberAtlas can link the exact number to a specific standards document and locator. A source URL elsewhere on a record does not by itself prove that its pressure value comes from that authority. Case and cartridge dimensions may still come from published SAAMI or C.I.P. standards where cited.
Trajectories come from a 2D point-mass integrator using the G1 drag function, with drag corrected for air density from temperature, altitude, barometric pressure, and humidity. The launch angle is solved for a level zero at the entered atmosphere, then retained for an inclined shot. Ranges follow the line of sight, with gravity resolved along and across it. Wind drift uses the lag-time method; spin drift and Coriolis corrections are not applied. Both drag models use the standard published reference tables (BRL/JBM G1 and G7) with a drag scale derived from the physics of standard air density — no fitted corrections — validated against manufacturer tables: across 8 factory loads from Federal, Hornady, Remington, and Winchester, predicted drop matches published tables within 0.31 MOA at every published distance and 0.12 MOA at 500 yards — see the accuracy page for the full comparison.
| Effect | Supported | Notes |
|---|---|---|
| Bullet drop | Yes | 2D point-mass integration with the selected G1 or G7 drag model |
| Wind drift | Yes | Lag-time method |
| Atmosphere | Yes | Air density from temperature, altitude, pressure, and humidity; one atmosphere along the path |
| Inclined fire | −60° to +60° | Line-of-sight ranges; fixed level zero retained for the inclined shot |
| Spin drift | No | This correction is not applied |
| Coriolis | No | This correction is not applied |
| Aerodynamic jump | No | Not modeled |
| G7 drag model | Yes | Used when a load supplies a G7 BC; checked against a publisher calculation using measured BC (see the accuracy page) |
Unless overridden: 1.5-inch sight height, 59°F, 29.92 inHg, sea level, and 50% relative humidity.
Retained-energy references of about 1,000 ft-lb (deer-class) and 1,500 ft-lb (elk-class) are read directly from the trajectory table and never extrapolated beyond it.
The G1 model is least accurate through the transonic zone (roughly Mach 0.9–1.2). Using the July 12, 2026 source audit with modeled results refreshed September 5, 2026, our published rimfire validation covers one load, CCI Mini-Mag .22 LR 40gr. Against CCI's table, modeled drop differs by at most 0.08 MOA across the published drop rows through 75 yards, while retained velocity differs by at most 4 fps through 100 yards. That is evidence for the tested load, not a universal rimfire accuracy bound. Treat other rimfire loads and any trajectory near or beyond transonic as estimates to confirm with measured dope. Centerfire predictions past the cartridge's supersonic range should also be confirmed with measured dope. A G7 value in a catalog record is not a claim that CaliberAtlas measured it; check the source notes for attribution. Loads without a G7 value compute under G1. One representative load is shown per cartridge.
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