Just gonna point out the sheriff in Nate Jones' story had a semi automatic pistol in a Wild West setting. I dunno, its not like One Piece does anything realistically but it still manages to bother me. Most of their firearms in the series at least look like they might belong there with some artistic license even if they don't function like regular flintlocks, while a revolver was a unique weapon for a mildly important member of a large scale criminal organization and other crazier stuff is in the hands of very important people or Franky, who can build that stuff because he's a straight up genius.