The Colorado class supplies the 16-inch example, an inch wider than the Queen Elizabeth class's gun. The diameter prompts the suggestion that two heads might fit inside the bore. The two-head remark is a tentative joke about scale, continuing the informal comparison with a person's head before the move to 18 inches.
Notable Point · 1:00-1:09
Colorado's 16-inch gun in human scale
The Colorado class's 16-inch bore prompts a joke that two heads might fit inside it.