Why wartime guns still used pounder names

Why were some Second World War guns still named by projectile weight rather than calibre?

The names reflected both manufacturing history and a familiar vocabulary that already told crews which weapon was meant.

The older projectile-weight labels persisted partly because of established manufacturing practice and partly because naval personnel already understood them. A two-pounder or six-pounder immediately identified a familiar weapon even when metric calibre descriptions were available. Technical terminology can outlast the system that originally produced it.