Usage Notes

Coordinates

• x: distance (downrange): Positive is the direction projectile leaves muzzle
• y: vertical (drop): Positive is up
• z: windage (horizontal): Positive is towards right

For Wind (ref conditions.py::Wind):

• direction_from = 0 degrees (12 O'Clock) is blowing from behind shooter.
• direction_from = 90 degrees (3 O'Clock) is blowing from shooter's left towards right.

Atmospheric calculations

From the U.S. Standard Atmosphere, 1976 model, from sea level to 11km altitude:

• H = altitude
• $g_0 = 9.80665 \text{ m/s²}$ (Gravitational constant at sea level)
• $T_0 = 288.15 \text{ K}$ (Standard temperature at sea level)
• $M_0 = 28.9644 \text{ kg/kmol}$ (Mass of dry air)
• $L_m = -6.5 \text{ K/km}$ (Temperature Lapse Rate)
• $R^* = 8.31432 \times 10^{-3} \text{ N·m/(kmol·K)}$ (Gas constant)

Standard temperature at altitude $T_m(H) = T_0 + L_m \cdot H$

Standard pressure at altitude $P(H) = P_b \left( 1+ \frac{H \cdot L_m}{T_m} \right)^{\frac{-g_0 \cdot M_0}{R^* \cdot L_m}} $

Common Ammo

.22LR 40gr

ammo=Ammo(DragModel(0.07, TableRA4), mv=Velocity.FPS(1100))).

5.56x45mm NATO SS109

dm = DragModel(bc=0.151, drag_table=TableG7, weight=Weight.Grain(62), diameter=Distance.Millimeter(5.56), length=Distance.Millimeter(21.0))
Ammo(dm, mv=Velocity.MPS(900))

.308 Winchester 155gr SMK

dm = DragModel(bc=0.22, drag_table=TableG7, weight=Weight.Grain(155), diameter=Distance.Inch(0.308), length=Distance.Inch(1.2))
Ammo(dm, mv=Velocity.MPS(900))

.308 Winchester 168gr SMK

dm = DragModel(bc=0.223, drag_table=TableG7, weight=Weight.Grain(168), diameter=Distance.Inch(0.308), length=Distance.Inch(1.282))
Ammo(dm, mv=Velocity.FPS(2750))

7.62x51mm NATO M118

dm = DragModel(bc=0.243, drag_table=TableG7, weight=Weight.Grain(175), diameter=Distance.Millimeter(7.62), length=Distance.Millimeter(32.0))
Ammo(dm, mv=Velocity.MPS(800))