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FRA380X4(Richelieu B turret-bore premature)

FRA380X4(Richelieu B turret-bore premature)
The last battleship guns developed by France, these weapons had an unfortunate war history.
Richelieu had fired only six shots from each of her guns during abbreviated gunnery trials on 13-14 June 1940 before she had to flee to Africa to escape the invading Germans. At the time of her escape, she carried 296 APC rounds, but only 198 quarter charges and her ammunition handling equipment was barely functional.

During the first day of the British attack on the French Fleet at Dakar in September 1940, Richelieu returned fire from Turret II - the crew of Turret I having been placed ashore to man coast defense batteries - but the two starboard guns of this turret both failed at the first salvo. The inner gun No. 7 was shattered and the outer gun No. 8 bulged with the rifling gashed for 8 meters (26 feet). Guns No. 5 and No. 6 remained in action for the rest of the first day, but the next day the gunnery crewmen were switched to Turret I. Rounds fired from this turret used propellant charges that produced less pressure than the ones used on the previous day and thus did not suffer bore prematures. However, these lower pressures also gave significantly less range than estimated which caused fire control problems. Richelieu fired a total of 24 rounds during both days of the battle but she failed to score any hits. A few days after the battle, the French attempted to clear No. 5 and No. 6 guns by fire, but No. 5 gun failed in the same manner as had No. 8 and the gun stuck in the recoil position at an angle of 15 degrees. After this, No. 6 gun was cleared by hosing down the charges and then removing them and the projectile through the breech.

The cause of these problems was eventually traced to a defective shell design. The original APC projectiles had 4 cavities in the base which were designed to accept cartridges containing toxic war gases. These cavities were protected by a base cap, but this broke under the pressure generated when the guns fired. Splinters from the broken base cap smashed through the gas cavities and into the burster charge which then detonated. After this incident, a new base cap was produced and the gas cavities were filled in with cement.