The Hatcher Formula is an attempt to mathematically evaluate the approximate effectiveness of pistol ammunition at incapacitating a person. Developed by Gen. Julian Hatcher in the 1930's, it uses the bullet momentum, frontal area, velocity, and a 'form factor.'

The formula is:

RSP = M * A * F

where RSP = Relative Stopping Power Index, M = Momentum of the bullet in foot pounds, A = Area of the bullet in square inches, F = Form factor derived from his observations with some additions for later bullet types. The table lists an RSP for each 'Form Factor', whether or not that form of bullet actually exists for a particular caliber or weight. The form factors presented below include:

0.70 Fully Jacketed Pointed

0.90 Fully Jacketed Round Nose

1.05 Fully Jacketed Flat Point

1.10 Fully Jacketed Flat Point (Large flat)

1.00 Lead Round Nose

1.05 Lead Flat Point

1.10 Lead Flat Point (Large Flat)

1.00 Jacketed Softpoint (unexpanded)

1.35 Jacketed Softpoint (expanded)

1.25 Lead Semi-wadcutter

1.10 Hollow Point (unexpanded)

1.35 Hollow Point (expanded)

Hatcher's Theory Of Relative Stopping Power

The standard Kinetic Energy equation (½mv²)uses kilograms and meters-per-second and yields Joules of KE.

In Ballistics Kinetic Energy is expressed in Foot Pounds (ft-lbs) rather than Joules. Furthermore, the standard equation usually uses 980.261 cm/sec (32.16 feet per second) as a standard, but in reality that number varies depending upon your position on the earth - different latitudes or altitutes have small differences in acceleration due to gravity. Since bullet weights are expressed in grains and velocity is in feet per second, in Ballistics, you see Kinetic Energy formulas expressed like KE = mv²/450240. (The mystery factor of 450240 is (7000 * 32.16 * 2) or (GrainsInPound * FeetPerSecond * 2). The table uses latitude 41º at sealevel (32.1607 ft per second).

**Hatcher's Theory Of Relative Stopping Power**