Brick House Accuracy & Gun Works
Downrange Dispersion Estimator — Planning Record
Generated Nov 9, 2026, 4:34 PM · Current on-screen inputs and outputs
Downrange Dispersion Estimator
A small group at 100 yards is important, but it is not the whole story. Analyze one recorded test or compare two to estimate a typical future group at distance and see how much of that spread comes from the original group versus velocity variation.
Enter measured group and chronograph data for one recorded test, or use a second test for comparison. The tool uses a matched G1 or G7 point-mass model internally to isolate velocity-sensitive vertical dispersion. It does not provide drop, holds, clicks, wind calls, or load guidance.
Test A
Optional label only. It does not add a bullet-specific adjustment.
Measured center-to-center extreme spread from this test.
Distance at which the group was actually measured.
Keep every valid shot in the entered group.
Use the measured average for this ammunition test.
The measured sample SD is the primary velocity-consistency input.
Optional context from the same chrono string. It must not be lower than SD.
The number of velocities used to calculate the SD and ES.
Use the manufacturer-published value that matches the selected drag model. No G1-to-G7 conversion is performed.
Choose one test when you want to understand its own projected spread. Add Test B only when you want a second line and a direct comparison.
Test B
Optional label only. It does not add a bullet-specific adjustment.
Measured center-to-center extreme spread from this test.
Distance at which the group was actually measured.
Keep every valid shot in the entered group.
Use the measured average for this ammunition test.
The measured sample SD is the primary velocity-consistency input.
Optional context from the same chrono string. It must not be lower than SD.
The number of velocities used to calculate the SD and ES.
Use the manufacturer-published value that matches the selected drag model. No G1-to-G7 conversion is performed.
Shown in 100-yard stations up to 1,000 yards, plus the selected final distance.
The simulated group size used for the expected future-group bands.
Atmospheric values apply to both tests. Use conditions representative of the downrange question—not a powder-temperature correction. If you do not know them, 59°F, sea level, and 50% humidity are conservative visible defaults.
Enter valid values to compare two recorded tests.
Opens your browser’s print dialog. Choose Save as PDF to keep this current planning record.