In addition to the rated number of carriage-mounted guns (which included the heaviest calibre available mounted on their lower decks, with smaller guns on the decks above), first rates also carried a number of anti-personnel guns, initially swivel-mounted weapons. From the invention of the slide-mounted carronade in the later 1770s, first rates (like other warships), could mount a number of these weapons on their quarterdecks and forecastles to augment their short-range firepower, but they were not included in the ship's rating until 1817 except where they replaced carriage-mounted guns.