The main armament of the new American battleships according to the Dutch magazine Marineblad dated 1920 no. 6

British Courageous-class battle cruisers

Briitsh aircraft carrier HMS Furious

An item referred to the American magazine Army and Navy Register reporting that the rumours that the US navy considered to arm the new American battleships with 18” in stead of 16” guns was not correct. It was mentioned that in the First World War in England 4-18” guns were manufactured placed on board of the HMS Furious (1) and 3 monitors. Lord Fisher (2) ordered that at Elswick [by Armstrong?] a test gun of 20” was manufactured. The shell for this gun weighed around 2,5 ton and was able to pierce over a distance of 10 miles still armour with a thickness of 30“. The calibre was to be used on board of the designed battle cruiser Incomparable (3) of which the building after the war was cancelled.

Notes
1. This must be the battle cruiser Furious laid down on 8 June 1915. Launched on 15 August 1916, commissioned n 26 June 1917, converted into an aircraft carrier during the building and sold to be broken up in 1940. Of the Courageous-class with 2x1-18“ guns. Her 18” guns were used for the Lord Clive-class monitors HMS General Wolfe and Lord Clive.
2. John ‘Jackie’Fisher (25 January 1841 Ramboda, Ceylon-10 July 1920 London, England), left the service as Admiral of the Fleet and was Firs Sea Lord in 1904-1910 and 1914-1915.
3. Building was proposed by Fisher on 1915 but apparently never designed. She was to have a standard displacement of 46.000 tons and as dimensions 304,8 x 31,7 x 7,3 (deep load) metres or 1.000 x 104 x 24 feet with an main armament of 3x3050,8cm/20” breech loading guns).