Generic class-name for any grenade launcher ammunition, becuase most of the weapons have 40mm calibre. Identifiable by the stubby size and rounded tip.
Notable examples are the 40×46 mm LV (low velocity) cartridge used by NATO and US forces, and the Soviet/Russian 40mm VOG-25 for GP-25 series.

External links

• Wikipedia: 40mm grenade

This tag implicates ammunition (learn more).