I second this, while the Mk. 6 16" gun had a slightly lower muzzle velocity than the Iowas Mk. 7, however, at the range that Washington would've pounded Yamato during the Battle off Guadalcanal, this would be irrelevant, especially since she too used the Mk. 8 "super heavy" round, and infact, in a longer ranged duel, the Mk. 6 might have had a slight edge over the Iowas guns in regards to penetrating deck armor, as the shells would have dived at a steeper angle due to losing energy faster. Now combined with also having superior radar fire control, the ability to shoot with accuracy even while making radical maneuvers, better damage control, and with the inclined STS armor, which as you mentioned in an earlier post, might actually provide better protection than Yamatos, I strongly believe that the South Dakota and North Carolina class' could also have a strong chance at beating Yamato.