When Britain and America nearly chose different 40 mm weapons

Which navies nearly chose the alternative to their familiar wartime 40 mm anti-aircraft weapon?

The United States nearly chose the pom-pom, while Britain nearly chose the 40 mm Bofors.

Two familiar wartime anti-aircraft systems emerged from a procurement crossroads. The United States nearly adopted the pom-pom, while Britain nearly moved toward the Bofors earlier. A momentary correction in the weapon name is audible, but the contrast is clear. Testing and institutional choice produced the fits later associated with each navy.