An ammunition cartridge comprising a casing body that defines a hollow interior configured to receive a projectile is provided. The casing body contains a polymer composition that includes a polyarylene sulfide and an impact modifier. The impact modifier includes an epoxy-functionalized polymer. Further, the polymer composition exhibits a notched Charpy impact strength of about 6 kJ/m2 or more as determined at a temperature of 23° C. in accordance with ISO Test No. 179-1:2010.