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Quick Start
Define your bullet, range, and variability parameters. Choose a circle or rectangle target shape. Click Run to fire the Monte Carlo simulation and view hit probability and dispersion statistics.
Ballistic Parameters
BC (Ballistic Coefficient): Aerodynamic efficiency. Higher = less drift and drop.
Drag: G7 for modern boat-tails; G1 for older/flat-base data.
MV (fps): Muzzle velocity in feet per second.
Weight / Diameter / Length: Bullet geometry and mass used by the trajectory model.
Twist (in/turn): Barrel twist rate (e.g., 8 for 1:8 twist).
Spin Effects: Includes spin drift and crosswind jump for realism.
Range (yd): Distance to the target the shots are fired at.
Shots: Number of shots to simulate; more shots give smoother statistics.
Target Shape
Circle: Defined by diameter in inches. Hit = impact landing within the circle.
Rectangle: Defined by width and height in inches. Hit = impact landing within the rectangle.
Variability Parameters (Standard Deviations)
MV σ (fps): Spread in muzzle velocity (lower = more consistent).
BC σ (%): Shot-to-shot ballistic coefficient spread, as a percent of BC, sampled from a normal distribution. Drives vertical dispersion at long range. Match-grade ≈ 0.4–0.6%, typical ≈ 0.8–1.2%, poor lots 1.5–2%+.
Cross Wind σ (mph): Side-to-side wind variability (main driver of horizontal spread).
H/T Wind σ (mph): Head/tail variability (small influence on drop).
Vert Wind σ (mph): Up/down air movement (usually minor).
Accuracy (MOA): Rifle+shooter precision; 1 MOA is about 1 inch at 100 yards.
Scope Cant (deg): Per-shot rifle tilt about the bore axis, drawn uniformly from −value to +value degrees; it trades some elevation hold for windage (and vice versa). Set 0 to disable.
Environmental Parameters
Altitude: Height above sea level in feet. Higher altitude reduces air density and drag.
Temperature: Air temperature in Fahrenheit. Warmer air is less dense.
Humidity: Relative humidity percentage. Higher humidity slightly reduces air resistance.
Statistics
Hit Probability: Fraction of shots landing inside the target shape.
Shots / Hits / Misses: Total shots simulated, and how many landed inside vs. outside the target.
Horizontal/Vertical Spread: Max X and Y extent of the group (inches).
Extreme Spread: Largest distance between any two impacts (inches). Exact up to 5,000 shots; above that it is a close bounding-box approximation.
Mean Radius: Average distance from group center (inches).
Radial Std Dev: Standard deviation of radial distances from center (inches).
CEP (50%): Circular Error Probable, the radius of the circle, centered on the group's center, that contains 50% of shots (inches).
Known Limitations
This list is not exhaustive. Additional limitations, errors, or inaccuracies may exist.
Simplified Wind: Wind drawn independently per shot from Gaussian distributions; constant along trajectory.
Accuracy Model: Uniform distribution within a circle (diameter = MOA setting).
Statistical Tool: This simulator is for exploring statistical patterns, not predicting real-world performance.
Full Disclaimers: See the
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