Exterior ballistics / aperture geometry

Loophole clearance calculator

A technical planning utility for modeling the projectile centerline and a conservative dispersion envelope through a recessed rectangular opening. The solver uses numerical point-mass integration with G1 or G7 standard drag.

INPUT DECKUS customary units

01 Projectile

Bullet weight gr Caliber in Muzzle velocity fps Ballistic coefficient BC Drag model standard Precision MOA ES

02 Geometry

Zero range yd Target range yd Sight over bore in Optic lateral offset in Aperture distance ft, front Aperture depth in Opening height in Opening width in LOS vertical offset in, + up LOS horizontal offset in, + right Added safety radius in

03 Atmosphere

Temperature °F Pressure inHg Pressure type reference Altitude ft, MSL Humidity % RH Wind speed mph Wind from clock

Altitude is applied only when pressure is sea-level corrected. Clock direction is the direction the wind comes from: 12 is a headwind; 3 is from the right.

APERTURE STATUSClear in model

MINIMUM CLEARANCE0.125 in

Elevation3.48 mil

Relative to 100 yd zero

Windage0.00 mil

Positive is right

Terminal velocity1,778 fps

1,228 ft·lbf

Time of flight0.698 s

Density ratio 0.997

SAFE LINE-OF-SIGHT WINDOW

Where the optic axis may cross the opening

Offsets from aperture center

Vertical-0.13 to 2.24 in

Horizontal-1.20 to 1.20 in

Opening Projectile envelope

Minimum centered opening for current LOS0.60 W × 2.75 H in

TRAJECTORY RELATIVE TO LOS

Near-field offset

Vertical and horizontal / inches

MODEL NOTES

Assumptions and limits

Point mass Standard G1/G7 retardation, measured BC, gravity, air density, and a steady three-dimensional wind vector. Spin drift, Coriolis, aerodynamic jump, and inclination are not modeled.

Clearance envelope Projectile radius + added safety radius + half the entered MOA extreme-spread diameter at each aperture plane. The full aperture depth is sampled.

Geometry The optical line of sight is straight and the rifle is level. Positive LOS offsets are up and right when viewed toward the target.

SAFETY / VALIDATION

This is an engineering estimate, not a firing authorization or substitute for a verified ballistic solver, direct measurement, qualified supervision, or a controlled range. Do not fire when the muzzle, projectile path, backstop, or target cannot be positively confirmed safe.