A study has been made of the adaptability of fin stabilized, discarding sabot projectiles to the 538 gun. Such a projectile has a definite time-to-target and range advantage over spin stabilized projectiles. Preliminary design details of fixed and semi-fixed t-inch rounds incorporating an FSDS projectile are presented. The designs are patterned after similar type projectiles which have been developed at NOLWO. These projectiles could be fired through rifled barrels interchangeably with standard spin stabilized ammunition but modifications to ammunition handling and fire control equipment would be required for compatibility with the FSDS round. The magnitude of the alterations involved would depend upon the efficiency desired in the overall system. The fixed round, one-piece ammunition offers several advantages in respect to stowing, handling and increased cyclic rate. Relative merits of utilizing the British 12759 mm round in the 538 gun are also discussed.