Howdy JSB,
"4- and they where not very useful (did they ever really fight anything) ? "
Barham was at Cape Matapan and helped sink the Italian cruisers. One of the R's was on convoy escort duty when Scharnhorst and Gneisenau intercepted the convoy. The sight of the R was enough for S & G not to attack fearing unrepairable damage in mid-Atlantic (I think the same thing happened with Malaya as well). The R's were at the Battle of Mers-el-kebir in 1940. The biggest problem with the R's were that they were just too slow for modern warfare. They were great as escorts and fire support ships.
But Matapan was at night and very close,
the British battleships Barham, Valiant and Warspite were able to close to 3,800 yards (3,500 m) unnoticed by the Italian ships—point blank range for battleship guns—from where they opened fire
None of the above suggests that unmodernised battleships ever fought at a range where the turrets would make a difference ?
(and could S&G tell what BB they might be running into ? i.e.. they don't know that the mast in front cant shoot at 30 deg until it happens or not).
I don't think the above actions really tell us if a 20deg ship could fight in a day battle with new ships.(and in 1920s radar/codebreaking cant be relied on)
JSB