FBP is a 9 mm submachine gun originally developed from a design first conceived in 1940 by Gonçalves Cardoso, an officer of artillery in the Portuguese Army.

The onset of World War II halted development of the weapon, which was further modified and put into production in 1948.

[4] Unusual for submachine guns, the m/948 was fitted with a barrel sleeve with a mount to accept the standard Portuguese Mauser bayonet.

The original version of the submachine gun (the FBP m/948) only allowed for fully automatic fire.

It was eventually replaced in service by the 9 mm Uzi and the collapsible-stock version of the standard m/961 G3 rifle.