Exterior ballistics trajectory mechanics
A projectile fired from a firearm follows a curved parabolic trajectory determined by initial muzzle velocity (V0), the G1 ballistic coefficient (BC), gravity, aerodynamic drag, and line-of-sight scope geometry.
Scope elevation corrections compensate for drop: 1 Minute of Angle (MOA) subtends 1.047 inches per 100 yards; 1 Milliradian (Mil / MRAD) subtends exactly 3.6 inches per 100 yards (10 cm per 100 metres).
Crosswind drift occurs because drag causes the bullet to lag behind vacuum flight time, causing Didion displacement along the wind vector.
Worked example: .308 Winchester 168gr MatchKing
A 168-grain .308 Win bullet with G1 BC of 0.450 zeroed at 100 yards leaves the muzzle at 2,700 fps.
At 400 yards, the bullet drops approximately 25 inches below point of aim, requiring a +6.0 MOA (+1.7 Mils) elevation turret adjustment, retaining over 2,100 fps and 1,600 ft-lbs of energy.
Ballistics calculator inputs
Muzzle Velocity
Speed of bullet exiting the barrel in feet per second (fps).
Ballistic Coefficient (BC)
Standard G1 aerodynamic drag efficiency rating.
CALCULATOR QUESTIONS
Bullet trajectory & drop calculator questions
What is the difference between MOA and MRAD (Mils)?
1 MOA equals 1/60th of a degree (~1.047 inches at 100 yards). 1 MRAD equals 1/1000th of a radian (~3.6 inches at 100 yards or 10 cm at 100 metres).
Why does sight height above bore matter?
Sight height defines the vertical offset between the crosshair line of sight and the barrel bore axis, determining the close-range trajectory crossover point.