Volley guns, organ guns and early implementations like the Puckle gun long predate the founding of the US. The ribauldequin was what...14th century? Also they were certainly aware of early "artillery" weapons firing hundreds of arrows at once invented centuries earlier in China & Korea. In fact, European armies started embracing the use of rockets as early as the 1780s.

These were educated men. They had an idea about how technology could improve and, more specifically, that technological development would first be applied to war.