K.626

K.626

Ballistics

The science behind the shot.

A practical reference covering internal, external, and terminal ballistics— plus field-ready calculators for energy, scope corrections, twist rate, and dope cards.

Internal External Terminal

The three parts of ballistics

01

Internal

What happens from ignition until the projectile exits the muzzle: pressure, burn rate, barrel length, and the velocity and spin the projectile leaves with.

02

External

What the bullet does in flight: gravity, aerodynamic drag, wind drift, drop, stability, and how the trajectory relates to your line of sight.

03

Terminal

What happens on impact: penetration, expansion, fragmentation, retained mass, and how bullet construction influences performance in the target medium.

Reference

Ballistic coefficient

Ballistic coefficient (BC) describes how well a projectile resists drag. Higher BC values generally indicate less deceleration in flight.

G1 BCs are common. G7 BCs usually track modern boat-tail, long-range bullets more consistently. Use whichever drag model and BC the bullet maker actually publishes for that bullet.

Reference

MOA vs MIL

1 MOA1.047″ at 100 yd10.47″ at 1,000 yd
1 MIL3.6″ at 100 yd36″ at 1,000 yd

Both are angular units. Neither is “better” in a vacuum—what matters most is matching your reticle, turrets, and dope to the same system and using one consistently.

Reference

Twist rate & stability

Twist rate is expressed as one turn in X inches. Lower numbers mean a faster twist. Stability depends on bullet length, caliber, velocity, and air density—not weight alone.

A quick exact spin formula: RPM = muzzle velocity × 720 ÷ twist (with twist in inches per turn).

Reference

Zeroing

A zero is the distance at which your line of sight and bullet path intersect by design. Your “best” zero depends on cartridge, target size, and how you plan to use the rifle.

Real trajectory prediction depends on verified muzzle velocity, atmospheric conditions, and the correct drag model—not just a catalog number.

Ballistics calculator suite

Calculator

Shot fundamentals

Select a common load to prefill the calculator, then adjust any value below for your actual ammunition and rifle.

Muzzle energy0 ft·lb
Momentum0 lb·ft/s
Power factor0
Sectional density0
Spin rate0 RPM
Recommended twist*—

*Greenhill is a classic approximation and not a substitute for a full stability calculation. It is included here as a quick reference only.

Calculator

Scope correction

MOA0 MOA
1/4 MOA clicks0
MIL0 MIL
0.1 MIL clicks0
MOA
MIL

Calculator

Dope card builder

Enter your known drop data by distance. K.626 converts it to MOA, MIL, quarter-MOA clicks, and tenth-MIL clicks, then plots the correction curve.

Distance (yd) Drop (in) MOA MIL ¼ MOA 0.1 MIL
Correction chart MOA & MIL by distance

Good data matters

Chronograph it. Verify it. Then trust it.

The best ballistic solution in the world still depends on honest inputs. Confirm velocity with real chronograph data, verify your zero, and true your dope in the conditions you actually shoot in.