The flintlock musket was the standard long gun of 18th and early 19th century warfare, and its two-stage report, the flash in the pan followed by the main blast, is instantly recognisable from pirate films and colonial battle reenactments. This clip is a generic user-uploaded effect with no documented source, but it circulates online like meme impact sounds: editors treat it as a vintage vine boom for history-themed punchlines, swapping it in where others would use pew pew laser shots or a gunshot. Its staying power comes from old-timey flavour that reads as dramatic and funny at the same time.