Green’s Dictionary of Slang

smoking pistol n.

an opium pipe.

1947

(con. late 19C) A. McLeod Pigtails and Gold Dust 157: A pipe called the ‘smoking pistol,’ it being a polished stem of bamboo, often mounted with silver, a ring of ivory at the mouthpiece, and a round earthenware, flat-faced bowl, with a tiny hole in the centre.