The effective range of a weapon is the range at which it will have a specific type of effect on a particular target. It is distinct from the weapon's absolute maximum range, which is the furthest it can throw a projectile in accordance with the laws of physics, and is only normally used for large artillery guns. As an example, the absolute maximum range of a Beretta M9 (aiming it up in the air like a mortar, and disregarding air resistance it should be aimed up at +45 degrees above the horizon) is 1,800 meters, while its effective range on a point target is just 50 meters.
Some weapons, typically explosive weapons with arming delays for operator safety and missiles which need to complete boost phases before their seeker activates or their tracker captures them, also have a minimum effective range. Below this range the projectile is either not armed and only functional as a kinetic impactor, or incapable of tracking and only effective against a perfectly stationary target.
Weapons designed primarily for anti-aircraft use often have their AA Ceiling quoted, which is a measure of the maximum vertical range at which they can successfully engage a target.
There are four main types of effective range figure:
Absolute maximum effective range
This is the threshold of the distance at which the energy of a round drops to the point where it can no longer be considered lethal: there is no accuracy requirement attached to it. It is sometimes quoted misleadingly in PR materials: for example, this is the range figure used in claims that the FN P90 is "effective" against unarmored targets at a range of 400 meters.
Maximum effective range on a point target
This is the range at which a weapon can hit a target, typically one the size of a human torso for small arms and one the size of a tank's hull for anti-tank weapons, with 50% of shots fired, when secured in a machine rest. It does not require the round to retain lethal energy at this range: if it does not, the absolute maximum effective range figure tends to be used instead.
Maximum effective range on an area target
Typically used for machine guns, this is the range at which a weapon lands 50% of shots inside an area of defined radius, hence the very high effective range figures for machine guns even compared to rifles firing the same caliber. As with range on a point target, it does not require the round to retain lethal energy at this range: if it does not, the absolute maximum effective range figure tends to be used instead.
Sniper rifle effective range
The range at which a "high" expert marksman can be expected to achieve a hit on a human-sized target at least 80-90% of the time. Because wind is such a huge variable of ranges more than 3-500 meters, depending on the weapon and ammo, the unstated percentage of hits is assumed and understood. While very much longer range shots have been made, they are usually the 3rd to 6th round out of the gun. The allow the use of the first shots to show the wing value.