Slog tipper Rich alerted me to the existence of Six-Gun Gorilla, a serialized novel from a British magazine that nearly disappeared entirely:
"Six-Gun Gorilla" originally appeared as a fifteen-part serial in the British story paper Wizard in 1939. Anonymously-written, and appearing alongside such immortals as Crispin Gaunt (the African railway adventurer-detective) and "Dr. Matto - the Man Who Knocked Out The World" (with his sleep-inducing Amazonian centipedes), Six-Gun Gorilla would have been consigned to the dung heap of pop culture history if not for E.S. Turner and his Boys Will Be Boys (1948), the landmark account of British magazine popular culture. Thanks to Turner, successive generations of readers have been tantalized by his description of the Six-Gun Gorilla and his lengthy attempt to avenge the murder of his human master.
I am a big fan of serialized pulp fiction, and I am a big fan of gorillas, which makes this the motherlode. You can download a PDF of the whole story for free—it's in the public domain—right here.