Armies of NATO’s Central Front by David C. Isby
CEP (CIRCULAR ERROR PROBABLE) is the mean distance at which a projectile will be offset from it’s aim point. The offsets break down roughly as:
50% of all projectiles will impact within the radius of the CEP.
90% of all projectiles will impact within 2.5 times the radius of the CEP.
99% of all projectiles will impact within 4 times the radius of the CEP.
EFFECTIVE RANGE. For tanks, this is the maximum range at which a trained crew under “quasi-combat” conditions can achieve a 50% first round hit probability against a stationary 2.5m2 target. The same formula is also used for anti tank weapons against armor. For automatic weapons, it is the longest range at which substantial losses are likely to be inflicted on a small area target.
BURST RADIUS. The distance from the impact point of a weapon at which its blast or fragmentation effects are likely to cause effective casualties.
PER (PROBABLE ERROR RANGE). An index of precision of an artillery piece. The smaller the PER, the more accurate the weapon. 50% of a weapons's "overs" (shells that fall beyond the target) and 50% of its "shorts" (shells that fall short of the target) will be within one PER (for that gun and range) of the mean point of impact. This figure is usually larger in the field than on paper.
PED (PROBABLE ERROR DEFLECTION) Similar to PER, but dealing with deflection. For rifled artillery it is much smaller than PER.
PROBABILITY OF HIT An estimate of the chances of a shell (or series of smaller projectiles) striking a specific target at a specific range. Most of these figures are taken from field tests or estimated on their results. Crew training and battlefield conditions can modify these results greatly.
PROBABILITY OF KILL The US army divides kills into K-Kills (total destruction of all combat ability), F-Kills (Firepower kills; destruction of the primary weapons system capability) and M-Kills (Mobility kills; destruction of the ability to move). The probability of kill represents the average chance of achieving one of these. The exact point at which a projectile strikes a target greatly affects the probability of kill.