Fired at the muzzle, a representative 9mm Luger load (8 g, FMJ, 360 m/s) reaches roughly 20 mm (0.8 inches) into polycarbonate. That is enough to defeat a typical barrier of this material — treat anything behind it as exposed.
About Polycarbonate
A polycarbonate pane (~12 mm); true bullet-resistant glass is far thicker and layered.