Revisionist history has Batman vowing never to use a gun in his war against crime, but actual history begs to differ.
The Original Bat Man was a true avenger of evil-- and he took no prisoners. As shown in the collection of early stories in Batman Chronicles Vol 1 he executed no fewer than 30 no goodniks in the span of just 10 issues.
Based on the pulp avenger The Shadow, it was no surprise that Batsy even spent some time with a .45 caliber automatic strapped to his hip.
Makes sense, if you're going to go out there and fight crime in long underwear, you want to bring some firepower with you.