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 enemies at extended ranges in open country. Other AR-10s were used by the paratroopers in a secondary role to launch rifle grenades. The AR-10's built-in gas cutoff design enabled it to fire Energa rifle grenades without adjustment of the gas system, and the self-loading action would even eject the spent blank shells and load the next one, allowing several grenades to be quickly fired. The added recoil took its toll on rifle stocks, and some Portuguese rifles were retrofitted with all-metal butt stocks to better withstand the strain caused by firing the heavy grenades. Additional sales of the AR-10 rifle were stymied after the Netherlands embargoed further shipments of the rifle to Portugal. Paratroopers deploying to Africa in later years were subsequently issued a collapsible stock version of the German Heckler & Koch G3 rifle. Nevertheless, the AR-10 continued in service with a few Portuguese airborne units, and was in use as late as 1975 in the Portuguese Timor (now East Timor) decolonization emergency.