The LAPA FA-03 was a rifle chambered in 5.56x45mm NATO, American M193 ammunition (55 grains), the barrel pitch was 1:12 (one round in 305mm); with plans for the future Belgian 62-grain FN SS109 standard ammunition, which would later be adopted as a standard by NATO. Production specimens would have barrels adapted for NATO's new SS109 ammunition.
The LAPA FA-03 rifle was designed to fire 5.56x45mm NATO cartridges, including American M193 ammunition (55 grains), with a specific barrel twist of 1:12 (one round in 305mm). The design also anticipated the adoption of Belgian-made 62-grain FN SS109 ammunition, which would eventually become a standard for NATO.