Furious retained ten of her original eleven breech-loading BL 5.5-inch Mk I guns, five on each side, for self-defence from enemy warships.
They fired 82-pound (37 kg) projectiles at a muzzle velocity of 2,790 ft/s (850 m/s).
Their maximum range was 16,000 yards (15,000 m) at their maximum elevation of 25°, and the rate of fire was 12 rounds per minute.

Half a dozen QF 4-inch Mark V guns replaced her original anti-aircraft guns.
Four were mounted on the sides of the flying-off deck and two on the quarterdeck.
They had a maximum depression of −5° and a maximum elevation of 80°.
The guns fired a 31-pound (14 kg) high explosive (HE) shell at a muzzle velocity of 2,387 ft/s (728 m/s) at a rate of 10 to 15 rounds per minute.
The guns had a maximum ceiling of 31,000 ft (9,400 m), but an effective range of much less.
The four guns on the flying-off deck were removed during trials of the lower flight deck in 1926–1927, but only two were replaced when the trials were concluded.

Four single QF 2-pounder pom-poms were installed by 1927.
During Furious's September 1930 – February 1932 refit, her anti-aircraft outfit was changed by the substitution of two 8-barrel 2-pounder pom-pom mounts for the forward 4-inch guns on the flying-off deck removed earlier.
The Mark V mount could depress to −10° and elevate to a maximum of 80°.
The Mark VIII 2-pounder gun fired a 1.6-inch (40 mm) 0.91-pound (0.41 kg) shell at a muzzle velocity of 1,920 ft/s (590 m/s) to a distance of 3,800 yards (3,500 m).
The gun's rate of fire was approximately 96–98 rounds per minute.

The 5.5-inch (140 mm) and 4-inch (102 mm) guns were replaced during Furious's refit in early 1939 by a dozen QF 4-inch Mk XVI guns in twin dual-purpose Mark XIX mounts.
One mount each was on the former flying-off deck and the quarterdeck while the other four were mounted two per side.
The Mark XIX mount could depress to −10° and elevate to a maximum of 80°.
The Mark XVI gun fired  fifteen to twenty 35-pound (16 kg) HE shells per minute at a muzzle velocity of 2,660 ft/s (810 m/s).
Against surface targets it had a range of 19,850 yd (18,150 m) and a maximum ceiling of 31,000 ft (9,400 m), but an effective anti-aircraft range of much less.
Two more Mark V 2-pounder mounts were added fore and aft of the newly added island at the same time.

During the Second World War, Furious, the only surviving ship of the three, received an eventual total of 22 manually operated automatic 20 mm Oerlikon light anti-aircraft (AA) guns, which replaced the single quadruple Vickers 0.50-calibre machine gun mount.
The Oerlikon fired a 0.272-pound (0.123 kg) HE shell at a muzzle velocity of 2,750 ft/s (840 m/s).
The maximum ceiling was 10,000 ft and the maximum range was 4,800 yd (4,400 m) although the effective range was under 1,000 yd (910 m).
The cyclic rate of fire was 450 rounds per minute, but the practical rate was between 250 and 320 rounds per minute owing to the need to reload magazines.

A mix of single-purpose anti-surface and anti-aircraft guns in various sizes was considered for Courageous and Glorious by the Admiralty, but was ultimately rejected for a dual-purpose armament of sixteen QF 4.7-inch Mark VIII guns in single high-angle mounts.
One mount was on each side of the lower flight deck and a pair were on the quarterdeck.
The remaining twelve mounts were distributed along the sides of each ship.
These mounts could depress to −5° and elevate to a maximum of 90°.
The Mark VIII guns fired a 50-pound (23 kg) HE shell at a muzzle velocity of 2,457 ft/s (749 m/s) at a rate of 8–12 rounds per minute.
The guns had a maximum ceiling of 32,000 ft (9,800 m), but an effective range of much less.
They had a maximum range of 16,160 yd (14,780 m) against surface targets.

During refits in the mid-1930s, both ships received multiple 2-pounder pom-pom mounts.
Courageous received three quadruple Mark VII mounts, one on each side of the flying-off deck, forward of the 4.7-inch guns, and one behind the island on the flight deck (two of these were transferred from the battleship Royal Sovereign).
Glorious received
Furious retained ten of her original eleven breech-loading BL 5.5-inch Mk I guns, five on each side, for self-defence from enemy warships. They fired 82-pound (37 kg) projectiles at a muzzle velocity of 2,790 ft/s (850 m/s). Their maximum range was 16,000 yards (15,000 m) at their maximum elevation of 25°, and the rate of fire was 12 rounds per minute.
Half a dozen QF 4-inch Mark V guns replaced her original anti-aircraft guns. Four were mounted on the sides of the flying-off deck and two on the quarterdeck. They had a maximum depression of −5° and a maximum elevation of 80°. The guns fired a 31-pound (14 kg) high explosive (HE) shell at a muzzle velocity of 2,387 ft/s (728 m/s) at a rate of 10 to 15 rounds per minute. The guns had a maximum ceiling of 31,000 ft (9,400 m), but an effective range of much less. The four guns on the flying-off deck were removed during trials of the lower flight deck in 1926–1927, but only two were replaced when the trials were concluded.
Four single QF 2-pounder pom-poms were installed by 1927. During Furious's September 1930 – February 1932 refit, her anti-aircraft outfit was changed by the substitution of two 8-barrel 2-pounder pom-pom mounts for the forward 4-inch guns on the flying-off deck removed earlier. The Mark V mount could depress to −10° and elevate to a maximum of 80°. The Mark VIII 2-pounder gun fired a 1.6-inch (40 mm) 0.91-pound (0.41 kg) shell at a muzzle velocity of 1,920 ft/s (590 m/s) to a distance of 3,800 yards (3,500 m). The gun's rate of fire was approximately 96–98 rounds per minute.
The 5.5-inch (140 mm) and 4-inch (102 mm) guns were replaced during Furious's refit in early 1939 by a dozen QF 4-inch Mk XVI guns in twin dual-purpose Mark XIX mounts. One mount each was on the former flying-off deck and the quarterdeck while the other four were mounted two per side. The Mark XIX mount could depress to −10° and elevate to a maximum of 80°. The Mark XVI gun fired  fifteen to twenty 35-pound (16 kg) HE shells per minute at a muzzle velocity of 2,660 ft/s (810 m/s). Against surface targets it had a range of 19,850 yd (18,150 m) and a maximum ceiling of 31,000 ft (9,400 m), but an effective anti-aircraft range of much less. Two more Mark V 2-pounder mounts were added fore and aft of the newly added island at the same time.
During the Second World War, Furious, the only surviving ship of the three, received an eventual total of 22 manually operated automatic 20 mm Oerlikon light anti-aircraft (AA) guns, which replaced the single quadruple Vickers 0.50-calibre machine gun mount. The Oerlikon fired a 0.272-pound (0.123 kg) HE shell at a muzzle velocity of 2,750 ft/s (840 m/s). The maximum ceiling was 10,000 ft and the maximum range was 4,800 yd (4,400 m) although the effective range was under 1,000 yd (910 m). The cyclic rate of fire was 450 rounds per minute, but the practical rate was between 250 and 320 rounds per minute owing to the need to reload magazines.
A mix of single-purpose anti-surface and anti-aircraft guns in various sizes was considered for Courageous and Glorious by the Admiralty, but was ultimately rejected for a dual-purpose armament of sixteen QF 4.7-inch Mark VIII guns in single high-angle mounts. One mount was on each side of the lower flight deck and a pair were on the quarterdeck. The remaining twelve mounts were distributed along the sides of each ship. These mounts could depress to −5° and elevate to a maximum of 90°. The Mark VIII guns fired a 50-pound (23 kg) HE shell at a muzzle velocity of 2,457 ft/s (749 m/s) at a rate of 8–12 rounds per minute. The guns had a maximum ceiling of 32,000 ft (9,800 m), but an effective range of much less. They had a maximum range of 16,160 yd (14,780 m) against surface targets.
During refits in the mid-1930s, both ships received multiple 2-pounder pom-pom mounts. Courageous received three quadruple Mark VII mounts, one on each side of the flying-off deck, forward of the 4.7-inch guns, and one behind the island on the flight deck (two of these were transferred from the battleship Royal Sovereign). Glorious received 
Courageous-class aircraft carrier