BBC Home Affairs Correspondent Vincent Kearney said it is possible the weapon was an AK47, which has previously been used in dissident republican attacks.
Up to eight shots struck the passenger side of the car parked at Rossnareen Avenue, at about 18:50 GMT on Thursday.
Two male officers who were in the car were not injured but were said to have been badly shaken.
Police described it as a "mindless, reckless attempt to kill officers". Dissident republicans are being blamed.
Ch Supt Nigel Grimshaw said the police car's armour-plating and bullet-proof glass had stopped the officers from being seriously injured or killed.
Detectives believe the attackers made off in a BMW car that had been waiting nearby at Tullagh Park.
The car, which was fitted with a false Republic of Ireland registration plate, was later found abandoned and on fire at Cluain Mor Drive in the Beechmount area.
Police described the gun used in the attack as "accurate firing".
One of the officers was looking through the passenger window when it was struck by two bullets.
A military assault rifle was used in an attack on a police patrol car in west Belfast.