The British 18-inch gun was not originally designed specifically for HMS Furious. Fitting it in the ship required shortening the barrel, which points toward an underlying 42- or 45-calibre concept rather than a purpose-built 40-calibre weapon. At this scale, removing several calibres meant cutting away feet of heavy gun tube to reduce the mass that had to be carried and moved. The weapon used a built-up, partly wire-wound construction method associated with contemporary British heavy-gun practice.
Notable Point · 35:50-37:43
Why HMS Furious carried a shortened 18-inch gun
The 18-inch weapon fitted to HMS Furious had been shortened for the ship, suggesting that the underlying design was longer than the familiar 40-calibre form.