Why the Royal Navy held so many spare four-inch barrels

Which navies kept large emergency stocks of naval gun barrels?

The Royal Navy had a large reserve of four-inch barrels. The US Navy is also thought to have held stocks, though in less useful calibres.

One recalled estimate puts the Royal Navy's four-inch barrel stock at three times its requirements, even with the large number of ships using the calibre. A replacement was already available whenever a worn barrel came in. The old barrel could then go for relining without making an appreciable difference to the reserve. The US Navy is also thought to have held spare barrels, although often in calibres it no longer wanted to use.