Battleships and cruisers in World War II did not use their massive main guns for anti-aircraft (AAA) fragmentation (frag) shells due to several practical, technical, and tactical reasons. While the idea of employing the heavy firepower of main guns against aircraft might seem appealing, these weapons were fundamentally unsuitable for the fast-paced, close-range requirements of anti-aircraft warfare. Here's why:
1. Design Purpose of Main Guns
Primary Role: The main guns on battleships and cruisers were designed for long-range engagements with enemy ships and land bombardments. These guns fired heavy shells (weighing up to several tons) over distances of 20 miles or more. Their primary function was to destroy armored targets, not to intercept fast-moving aircraft.
Inappropriate Ammunition: The standard shells for main guns—armor-piercing (AP) and high-explosive (HE)—were not optimized for producing widespread fragmentation clouds needed to effectively damage aircraft. Designing and carrying specialized frag shells for main guns would have been inefficient and logistically burdensome.
2. Rate of Fire and Target Speed
Slow Rate of Fire: Main guns had a firing rate of about 1-2 rounds per minute, far too slow to engage fast-moving aircraft effectively. In contrast, smaller anti-aircraft guns like the 40mm Bofors or 20mm Oerlikon could fire hundreds of rounds per minute, saturating the sky with fire.
Aircraft Speed and Maneuverability: Aircraft in WWII typically flew at speeds of 200-400 mph and were highly maneuverable. The slow firing rate and cumbersome aiming systems of main guns could not keep up with such targets.
3. Fire Control Challenges
Tracking Fast Targets: The fire control systems for main guns were optimized for slow-moving or stationary targets like ships and shore installations. They lacked the speed and precision to track fast, erratic aircraft.
Inefficient Targeting: Engaging aircraft required rapid adjustments in elevation and bearing, which large gun turrets could not achieve quickly. Smaller anti-aircraft mounts were far more agile and better suited to the task.
4. Ammunition Handling and Logistics
Size and Complexity: Main gun shells were enormous, weighing hundreds or even thousands of pounds. Loading and firing these shells was a slow, labor-intensive process. Using such large weapons for anti-aircraft defense would have been a logistical nightmare.
Space Limitations: Ships carried a finite amount of ammunition. Dedicating storage space to specialized anti-aircraft shells for main guns would have reduced the availability of primary ammunition needed for surface combat.