The RPGs in the game are so slow that even if you're only 20 feet from a passing car you still need to lead it by a whole car length just to hit it. It seems like the RPGs only travel around 60-80 mph... IRL they travel 300 m/s...
Does the "rule of cool" apply here or should they be more realistic?
Also, there's a huge bug when firing RPGs. The rocket should leave the tube so fast it's IMPOSSIBLE to change the trajectory by turning. But in game, if you snap your aim somewhere else up to ~200 ms AFTER firing the RPG, it will be fired at the new aimpoint. Try it. Fire an RPG and then snap your aim somewhere else really fast. The RPG (that should have already left the tube) will be "re-aimed"