The 4.5-inch weapon inherited an 80-degree requirement from its anti-aircraft origins, while the 4.7-inch destroyer guns were designed around low-angle attacks. Norway illustrates how an aircraft could pass through the lower-angle flak zone and then approach with less heavy-gun interference. Greater elevation would not guarantee a kill, but would lengthen the time an attacking formation had to manoeuvre under fire. Redirecting 4.5-inch development money could also have improved the older 4.7-inch shell, which had otherwise been accepted as good enough.
Notable Point · 44:51-49:45
Why 80 degrees matters against dive-bombers
A mount reaching roughly 80 degrees could keep firing as a diving aircraft closed, unlike the 50-degree destroyer guns that left a dangerous gap near the ship.