A fast action is useful only if the breech safely contains increasing pressure at sea. Under the definition used here, "quick firing" means at least twelve rounds per minute in all conditions. The quick-firing 4.7-inch gun therefore depended as much on rapid, secure breech closure as on moving ammunition. As shells grow toward the roughly 100-pound six-inch round, theoretical rates collide with human endurance. Realistic sustained fire required rotating loaders and continuously feeding ready-use positions from elsewhere in the ship, turning rate of fire into an ammunition-supply and personnel problem.
Chapter · 32:36-50:38
Quick-firing guns meet breech pressure and shell weight
The rise from small quick-firing weapons to 4.7-inch and six-inch guns shows why sealing and human endurance constrained practical fire rates.