"Napier, keep your .38 strapped to your calf until you're off Swannekke, and for a long time after. "
Smith & Wesson 10-6 .38 Special caliber revolver. 1970s vintage 4
Public Domain Smith & Wesson 10-6 .38 Special caliber revolver. 1970s vintage 4" gun - It may seem familiar from 1970s US cop dramas.

The .38 refers to the loaded diameter of the case and not the gun. The Smith and Wesson .38 special was standard for most police departments in America from the 1920s to the early 1990s. The cartridge is very accurate when used in a well-made revolver, produces little kickback and remains the most popular in the world.