I’m reading about the great northern war and theirs stuff like the streltsey using an axe along with their gun as well as Swedish infantry noted for drawing swords and charging after firing a volley. Reading about these historical tactics I’m left scratching my head and asking where are these peoples guns going? Are they dropping them on the ground? Carrying them on their backs while fighting? Both options seem impractical.
As the sling was a later invention, yes, if a musketeer wanted to fight with a sword he had to drop his musket, so this sounds a bit unlikely. Not sure about Gustavus Adolphus' Swedish army in particular, but for most European armies by the 1640's there would be a mix of soldiers armed with matchlock muskets and pikemen. The musketeers would advance, the front rank would fire, and while it was reloading the next rank would step through and fire. This was repeated a few times until the opposing force was close, then the ranks would charge forward and the pikemen would engage, and in the melee the musketeers would swing their guns like clubs. Swords you would expect in the hands of officers ( who would not carry muskets) or cavalry, however, so certainly after a few volleys you would expect the officers to draw their swords: they were likely already drawn.
Firth, Charles. (1902)Cromwell's Army. Methuen & Co. https://archive.org/details/cromwellsarmy0000firt