The Brazilian Navy has recently armed its Piratini-class patrol ships – NPa Piratini (P10), NPa Pirajá (P11), NPa Penedo (P14), and NPa Poti (P15) – with manually controlled 20 mm Oerlikon GAM-B01 gun mounts, replacing the 20 mm pedestal-mounted Oerlikon Mk 10 gun system. The boats also are armed with 12.7 mm machine guns. The Oerlikon 20 mm cannon is a series of autocannons, based on an original German 20 mm Becker design that appeared very early in World War I, with various models employed by both Allied and Axis forces during World War II, and many versions still in use today. The gun system installation is meant to upgrade the ships with newer weapons and was co-ordinated by the Navy Weapon Systems Directorate and performed by the Navy Systems Maintenance Center, the River Base of Ladário, and personnel of the flotilla.
The six Piratini-class patrol boats are a series of patrol vessels that were built for the Brazilian Navy at the Rio de Janeiro Navy Arsenal. Based on the United States Coast Guard Cape-class cutter design, they were built between 1970–1971 as coastal patrol vessels. In 1993 they were moved from coastal patrol to riverine patrol. The patrol fleet is fielded by the Mato Grosso Flotilla Command of the 6th Naval District Command of Ladário in Mato Grosso do Sul state. It is mainly used to patrol rivers in the states of Mato Grosso and Mato Grosso do Sul. The boats also are armed with 12.7 mm machine guns.