The range of a 5" gun on a ship is about 17 thousand yards, horizontal. It can fire either a proximity flak round or high explosive. It can use the land and sea modes as well as manual. The proximity flak shell is trigured by a magnetic sensor causing it to detonate when it is close to a target. Hitting the target isn't required, but sure does a good job when it does =o)
It seems the AI ship ack starts firing at about 8 thousand yards. The icon of the plane becomes visible just under 6 thousand yards. It becomes fairly easy to hit an enemy target at 5 thousand yards. At 3 thousand yards (9000 feet) an enemy plane faces almost certain death, unless it is doing some major maneuvering. A plane doing a rope-a-dope over a carrier topping out at 3 or 4 thousand yards is suicidal.
I commonly kill at 3K, am not surprised to kill at 5K and have killed at 10K or more (which has irritated a few =o). Someone really good, like Whels I suspect, can probably flick a fly off your windshield at 3K.
Flying directly at or away from the ship takes a death wish. A formation of buffs flying just above the water at a CV are a gunner's delight. The hardest thing to hit is a formation of heavey buffs coming in at 10,000 feet or more. There are three planes to hit and each requires so many hits to take it down it's really tough to accomplish before they pickle their bombs.
The nemisis of the 5 inch guns is the planes and PT boats surrounding the carrier. They trip the proximity fuse before it can reach the enemy.