Within a short time, the Portuguese Army saw the need for a modern selective-fire combat rifle, and in 1961 adopted the 7.62×51mm NATO caliber "Espingarda m/961" (Heckler & Koch G3) as the standard infantry weapon for most of its forces, that would be produced in large quantities in the Fábrica do Braço de Prata, a Portuguese small arms producer. However, quantities of the 7.62×51mm FN and Belgian G1 FAL battle rifle, known as the m/962, were also issued; the FAL was a favored weapon of members serving in elite commando units such as the "Caçadores Especiais". At the beginning of the war, the elite airborne units ("Caçadores Pára-quedistas") rarely used the m/961, having adopted the modern 7.62 mm NATO ArmaLite AR-10 (produced by the Netherlands-based arms manufacturer Artillerie Inrichtingen) in 1960. In the days before attached grenade launchers became standard, Portuguese paratroopers frequently resorted to the use of ENERGA anti-tank rifle grenades fired from their AR-10 rifles. Some Portuguese-model AR-10s were fitted with A.I.-modified upper receivers in order to mount 3× or 3.6× telescopic sights. These rifles were used by marksmen accompanying small patrols to eliminate individual enemy at extended ranges in open country. After the Netherlands embargoed further sales of the AR-10, the paratroop battalions were issued a collapsible-stock version of the regular m/961 (G3) rifle, also in 7.62×51mm NATO caliber.