Dane Hartman. Duel for Cannons (1981) (Dirty Harry #1) 173 pp. [pbo]
Publishers description: Dirty Harry Callahan blasts his way from the mean streets of San Francisco to the blazing byways of San Antonio. His target—a crime boss whos got the whole town, including the cops, under his thumb. Harrys all alone now, with nothing but a .44 Magnum and a bagful of dirty tricks between him and instant death!
Setting: San Francisco; San Antonio (Tex.)