When Koba steals an Armored Security Vehicle class M1117A Guardian, he kills the gunner from the turret and then somehow manages to use the 240B attached to the turret. First, it takes three men/apes to operate the ASV, and second, the ASV cannot be operated from the turret. In that scene, it is assumed that Koba is operating the entire vehicle, something most humans cannot do or do not know how to do. Let alone a 240B, MK19, or .50 Cal M2 Browning. The ASV turned in the direction of the wall, which was the only way that the Apes were able to breach the city walls. This is also kind of an important plot hole blunder too because if it were not for the breach from the ASV, the Apes would not have won. The other blunder from this is that the gunner would not have been exposed from the hatch, since the ASV was using .50Cal and MK19. No need to use the 240B.