The Israeli commission of inquiry into the Hebron massacre heard expert testimony today that supported assertions by the army that the killings were the work of a lone gunman. The testimony by police ballistics experts produced no evidence to back up assertions by Arab survivors of the massacre on Feb. 25 that there had been more than one source of gunfire in the mosque, where at least 29 worshipers were killed. Inspector Lior Nedivi of the police ballistics lab testified that of 115 bullet casings found in the shrine, 109 had come from the Israeli-made Galil rifle found near the body of Dr. Baruch Goldstein, the Jewish settler who had carried out the attack. Five casings came from the Galil rifles of two soldiers who had fired several shots as Arab worshipers began fleeing the Cave of the Patriarchs shrine. One Galil casing could not be traced, the inspector said.