Furlong enrolled with the Canadian Army and served with the 3rd Battalion, Princess Patricia’s Canadian Light Infantry.
In March 2002, Furlong participated in Operation Anaconda in Afghanistan’s Shah-i-Kot Valley. His sniper team included MCpl. Graham Ragsdale (Team Commander), MCpl. Tim McMeekin, MCpl. Arron Perry, and Cpl. Dennis Eason. A group of three Al-Qaeda fighters were moving into a mountainside position when Furlong took aim with his Long Range Sniper Weapon (LRSW), a .50-calibre McMillan Brothers Tac-50 rifle, loaded with Hornady A-MAX 750 gr very-low-drag bullets. He began firing at a fighter carrying an RPK machine gun. Furlong’s first shot missed and his second shot hit the knapsack on the target’s back. The third struck the target’s torso, killing him. The distance was measured as 2,430 m (2,657 yd). With a muzzle speed of 823 m/s (2,700 ft/s), each shot reached the target almost four seconds after Furlong fired. This became the longest sniper kill in history at the time, surpassing the previous record set by his teammate, Master-Corporal Arron Perry, by 120 m (130 yd).
This feat is not typical for the effective range with a high first-hit probability of the employed rifle on non-static targets (see maximum effective range). The shot was aided by the ambient air density in the Shah-i-Kot Valley where Corporal Furlong operated, which is significantly lower than at sea level due to its 2,700-meters (9,000 ft) mean elevation.
In December 2003, PPCLI snipers Master Corporal Graham Ragsdale, Master Corporal Tim McMeekin, Corporal Dennis Eason, Corporal Rob Furlong and Master Corporal Arron Perry were awarded the Bronze Star Medal by the U.S. Army for their actions in combat during Operation Anaconda, March 2–11, 2002. Rob Furlong held the record of longest kill shot recorded in history until November 2009 when his record of 2,430 m (2,657 yd) was beaten by Corporal of Horse (CoH) Craig Harrison, of the Blues and Royals, part of the Household Cavalry of the British Army, who set a new record by shooting two Taliban fighters at 2,475 m (2,707 yd), using a .338 Lapua L115A3 Long Range Rifle.