First time trying these shells - Sterling 12 Gauge 00 Buck 9 Pellet 2 3/4 in Shotgun Buckshot Ammunition

Tried the sterling 12 gauge 00 shot 23/4 in shells in my shotgun (target practice) the third shot the gun jammed dropped the mag and cleared the chamber notice the shells had failed the clear cover had cracked opened and the shots were falling out the chamber