A high strength polymer-based cartridge casing can include a first end having a mouth and a neck extending away from the mouth. Next, a shoulder extends below the neck and away from the first end. The cartridge can be have a frangible portion capable of being split upon discharge of a projectile. The shoulder can have unequal outside and inside shoulder angles. The casing can also include an insert having a rim at one end or a plurality of ribs extending longitudinally along a wall between the shoulder and the bottom of the cartridge and spaced radially from each other around a circumference of the wall. A projectile can be disposed in the mouth and a relief can be disposed on the neck near the mouth and projectile. The relief can form a gap between the neck and the projectile to receive an adhesive.