The LA-set film centres on a hustler (Howard) with unrealised Hollywood dreams who becomes wrapped up in a world of intrigue after being mugged, Deadline reports.
Killer Joe's Juno Temple, Christopher Walken and Luis Guzmán round out the cast, while Filip Jan Rymsza will direct from his own script.
Filming on A Girl and a Gun is set to begin this autumn.
Howard will next be seen in Kristen Stewart-starring adaptation On the Road.
He has just completed a role opposite Colin Farrell in thriller Dead Man Down, and is currently filming Lee Daniels's The Butler.
Watch the trailer for On the Road below: