40mm XM663 Star Cluster Grenade (Green)

Overview: The XM663 Star Cluster Grenade is a 40mm pyrotechnic signaling round designed for use with under-barrel grenade launchers (UBGLs) such as the M203, M320, and similar platforms. It is used primarily for battlefield signalling, target marking, and identification, deploying multiple bright green star flares that ascend into the air upon launch.

Development & Background: The XM663 was developed as a variant of the M585 Star Cluster, offering a distinctive green flare effect for mission-specific signaling. Upon launch, the grenade ejects five to seven bright green star flares, which rise to an altitude of approximately 200–250 meters before igniting and descending slowly. The use of color-coded flares allows for differentiation between signals, reducing confusion in multi-unit operations or joint-force engagements

Service & Usage: The XM663 Star Cluster Grenade is primarily used for battlefield coordination, aerial target marking, and friendly unit identification in low-light conditions. The green star cluster is often used for pre-arranged signals between ground and air forces, marking safe zones, or providing direction to allied troops. It is part of a series of star cluster grenades, including the M585 (White) and XM664 (Red), allowing for color-coded battlefield communication in night operations and complex engagements.