7.7 mm Lewis Machine Gun Model 92 (1932)
The Lewis type machine gun is used widely by the Japanese. Markings on a number of these guns found in the New Georgia area indicate that the weapon as used by the Japanese is of naval origin. It is also believed that the gun is used extensively for ship or air base protection as the tripod mount is adaptable for antiaircraft fire.
http://www.lonesentry.com/ordnance/tag/machine-gun
The sailor manning the AA gun in the tub can be seen operating a Type 92 7.7 mm machine gun (center) while the one aft of the tub (left) uses the Type 76 13.2 mm machine gun.
sources :
13.2 mm Type 76 machine gun :
http://www.navweaps.com/Weapons/WNJAP_13mm-76_mg.htm
7.7 mm lewis gun :
http://www.navweaps.com/Weapons/WNJAP_77mm-87_RU.htm
keltos