The British .50 Cal Spotter round was specifically designed for use with the 120mm Wombat (Weapon Of Magnesium, Battalion, Anti-Tank), an anti-tank recoilless rifle developed in the 1950s. This unique spotting system was created to enhance accuracy and precision in targeting enemy armor.

The .50 Cal Spotter round was a special tracer round that closely mimicked the trajectory and ballistics of the main 120mm high-explosive anti-tank (HEAT) round. Its primary purpose was to aid the gunner in aligning the weapon before firing the larger, more destructive ammunition. Equipped with a small explosive charge and a smoke tracer, the spotter round allowed soldiers to see the projectile's path, providing immediate feedback for adjustment.

This system was highly effective in training scenarios and combat, as it enabled operators to conserve valuable HEAT rounds and quickly correct aiming errors. The spotter round was fired from a coaxial spotting rifle mounted alongside the main barrel of the Wombat. The design emphasized practicality and cost-effectiveness, significantly increasing the weapon's overall efficiency by reducing the chances of missed shots against enemy tanks.

Ultimately, the .50 Cal Spotter round contributed significantly to the Wombat's reputation as a powerful and reliable anti-tank weapon during its service life.