The following weapons were used in the film Son of Godzilla:
Marlin Model 336 (Replica)
Nearly all of the characters use this lever action rifle that resembles a Marlin Model 336 throughout. Likely flash paper non-guns due to the kind of muzzle flash and the smoke they produce. They are used several times to engage Kamakuras, a giant praying mantis species living on the island.
Marlin 336A Carbine - .30-30 Carbine
Reporter Goro Maki (Akira Kubo) holds his rifle at a juvenile Kamakuras while Dr. Tsunezou Kusumi (Tadao Takashima) tries to phone for help.
Goro keeps his rifle up as he and Kusumi back into hiding.
Goro keeps his rifle on the passing mantis whilst motioning for Kusumi to stay put.
The scientists fire at Kamakuras.
The scientists fire at Kamakuras. Kamakuras is by far one of the weakest kaiju in the series, but he's still durable enough to survive small arms fire.