The expanding reach of interwar anti-aircraft guns

The 1926 comparison gives a single 4.7-inch anti-aircraft gun a theoretical coverage area of 686.28 square kilometres, described as about 80 percent of New York City's area. Its mounting can elevate from about -5 to +90 degrees. The quoted maximum range is 16,160 yards, or 14.78 kilometres, at 45 degrees, with a ceiling of 32,000 feet at 90 degrees. The Mark VIII pom-pom is assigned 120.76 square kilometres of coverage with an unobstructed 360-degree field of fire, compared with 3.8 square kilometres for the earlier Mark II. The comparison concentrates on specialist air-defence weapons so that their development can be followed through to missiles. In the destroyer counterfactual, continued development of the 4.7-inch gun and especially its mounting would have reduced Royal Navy losses in the Second World War.