Some 2000 basalt ballista balls (some still strewn along the wall and unrecorded yet) have been found to date. As opposed to arrowheads, which would have been collected (see below); this probably represents more or less the complete inventory of ballista balls that were deployed at Gamla. The concentration of ballista balls and arrowheads was greatest in and around the large breach, where clearly an artillery barrage took place (see above), but most buildings next to the wall, including the synagogue hall, were filled with them, providing a dramatic visualization of the siege. In the synagogue hall itself 157 balls were collected. Near the round tower some 130, while near the entrance just above the synagogue about 100.

At the foot of the twin towers of area M (10 on plan), on the inside, a concentration of several dozen ballista balls was found . Apparently, at night the defenders would gather the balls that had fallen in the city and hurl them back by hand at the Romans the following day. Ballistae had an effective range of c. 350–450 meters at most (Holley 1994:361). The furthest balls were found in areas S (3) and R (2), some 300m from the wall. These are among the smallest and lightest, as lighter balls would have traveled farther. Thus, the ballistae themselves were placed at most some 300 meters from the wall, and as the attack inside the city progressed, some machines were brought closer to the wall. There were probably several emplacements along the wall, though it cannot be determined exactly where. The edge of the Deir Qaruh spur that has been suggested (Gichon 1987:79) is probably beyond firing range. In the cut made in the mountainside during the construction of the service road to the expedition camp, a large pile of ballista balls was discovered. It is situated c. 300 meters from the wall, so it could be a ballista emplacement, but it could just as well be the spot where the balls were manufactured from locally collected basalt.