Why a 5.1-inch gun would barely change wartime destroyer conversions

How would a 5.1-inch/50-caliber gun change Second World War destroyer conversions?

Very little, because the conversions emphasized anti-submarine and anti-aircraft work and used readily available stored weapons.

A new 5.1-inch/50-caliber gun would have little effect on most wartime destroyer conversions. Those programs usually sought better anti-submarine reach and air defense rather than stronger surface gunfire. Production pressure also encouraged navies to fit weapons that already existed in large numbers, including guns removed from older ships. Flower-class corvettes illustrate the same wartime logic: available equipment that met the mission was more valuable than the newest theoretical choice. The new caliber would therefore struggle to displace established stocks and conversion priorities.