Initially, the 5.5 inch gun fired a 100-pound (45 kg) shell, using four charges in two cartridges to give a maximum range table muzzle velocity of 1,675 feet per second (511 m/s) and a maximum range of 16,200 yards (14,800 m).

In 1944 an 82-pound (37 kg) shell was introduced along with Charge Super giving a maximum muzzle velocity of 1,950 feet per second (590 m/s) and a range of 18,100 yards (16,600 m) yards.
 The new lighter shell contained 1.5 pounds (0.68 kg) more explosive and gradually replaced the older, heavier shell.

In addition to high explosive rounds, there were several types of chemical shell weighing between 90 and 98 pounds (41 and 44 kg) and 100-pound (45 kg) coloured smoke shells; coloured flare shells were also developed.
After World War 2, only HE was used.
There was no AP (armour-piercing) round for the gun but, in an emergency, gunners were taught to remove the impact fuze and fire the unfuzed high explosive as an AP substitute.

The normal HE fuze was No 117, a percussion, impact fuze that was introduced in 1920 and saw use until the 1960s.
In late 1944, the T100 proximity fuze became available.
Initially, the 5.5 inch gun fired a 100-pound (45 kg) shell, using four charges in two cartridges to give a maximum range table muzzle velocity of 1,675 feet per second (511 m/s) and a maximum range of 16,200 yards (14,800 m).
In 1944 an 82-pound (37 kg) shell was introduced along with Charge Super giving a maximum muzzle velocity of 1,950 feet per second (590 m/s) and a range of 18,100 yards (16,600 m) yards.  The new lighter shell contained 1.5 pounds (0.68 kg) more explosive and gradually replaced the older, heavier shell.
In addition to high explosive rounds, there were several types of chemical shell weighing between 90 and 98 pounds (41 and 44 kg) and 100-pound (45 kg) coloured smoke shells; coloured flare shells were also developed. After World War 2, only HE was used. There was no AP (armour-piercing) round for the gun but, in an emergency, gunners were taught to remove the impact fuze and fire the unfuzed high explosive as an AP substitute.
The normal HE fuze was No 117, a percussion, impact fuze that was introduced in 1920 and saw use until the 1960s. In late 1944, the T100 proximity fuze became available.
BL 5.5-inch medium gun