As a former battleship sailor, I'll reply to that. I served aboard the USS Iowa from 6/85 to 12/89. I was a technician in Guided Missile Div., Weapons Dept. There is no weapon on earth like those 16" guns. The ability to stand offshore 20 miles and deliver 1900-2700# projectiles at 2500 FPS, capable of penetrating and destroying hard targets like bunkers, steel mills, bridges, etc, one after the other for days or weeks if necessary, is unmatched. With good spotting by radar or aircraft, we destroyed truck-size targets from over the horizon during gunnery exercises. It is only since the Iraq and Afghanistan wars that effective modern bunker-buster aerial bombs have been developed, and it would take many aircraft sorties to deliver the hundreds of tons of ordnance carried in a battleship's magazines.That is the primary reason the Iowa-class ships were recommissioned in the 1980's. At that time, they also became cruise missile platforms.
Barrel life in large naval guns is not limited to a fixed number of rounds. The type of projectile and propellant charge determine the barrel wear per shot. When firing at shorter ranges, for example, reduced charges are used, which cause less barrel erosion. The determination to replace was made by gauging the actual wear in each barrel.
And for required freight car content, I recall steaming up the York River to take on ammunition at the NWS Yorktown. Ammo was brought to the pier by GE switchers toting ancient but immaculate non-interchange USN (steam-era) boxcars that never left the base. Unfortunately no photos were allowed.
Most Navy floating cranes are barge-mounted, and have numbers rather than names. When the Iowa was based at Norfolk, the nearby naval shipyard in Portsmouth, VA was our repair depot. For a job like changing gun barrels, the large pier-side cranes in the shipyard would be the preferred tool. We sometimes onloaded things like Tomahawk missiles or heavy transmitter parts from a crane bobbing alongside, and even in the calm of the harbor, it was spooky and dangerous.
Thanks for stimulating these memories, I've enjoyed following the conversation.