Like SASS, Cowboy Action, and The Wild Bunch, there is a small but enthusiastic group that likes to dress in and shoot Prohibition Era period correct accessories.
I don't know if they drive flat head Ford V-8s or not.
In one of Bogarts movies, he ementioned a Webley. A cut down Webley would fit nicely in a 'Zoot Shooters' arsenal.
Mob guns would fit right in with that crowd.