This is the predecessor of the 7.62×24.5mm sub caliber cartridge and was used as an anti-tank spotter round. It was phased out of service when the 7.62mm became standard, although it remained in use to some extent. The case was not based on the modification of any other existing case type and ordinary ball as well as tracer were produced. According to “Cartuchería Española” by Molina-Orea, it was designed by Spanish Lieutenant Colonel Gervasio González Regaña, but manufactured in Portugal. It was intended for the M-76 sub-caliber (Built by Ramen, S.A. of Madrid) for the Instalaza M-65 grenade launcher.