Why the Argencourt concept uses 18-inch/45 guns

Would the proposed Argencourt's 18-inch guns be 40- or 45-calibre weapons?

The reconstruction uses 18-inch/45 guns, interpreting Furious's shorter weapons as cut-down versions, but the original Argencourt connection remains uncertain.

The surviving Furious weapons were constrained by the small hull and are described as cut-down guns. A longer 18-inch/45 weapon may therefore have preceded them in design work. That hypothetical original can be connected to Argencourt, although the evidence remains circumstantial. This reasoned reconstruction should not be mistaken for a confirmed historical specification.