edit- follow up question
“a well regulated militia”. since the amendment was passed, and since the US has a military, has there even been a militia? would you trust your random neighbours loading up and marching against something? or would you expect law enforcement to crush it?
seems like the amendment has become “the locals can have guns and murder each other”. Nothing to with a “militia”; or defending your country.
Repeating rifles existed back then. The founders being well read would have been aware of their existence. Some of these repeating rifles were in use on the frontier. The Girardon air rifle could shoot 20+ rounds and was famously used by the Lewis and Clarke expedition.
https://en.wikipedia.org/wiki/Girardoni_air_rifle
https://arizonadailyindependent.com/2018/03/11/multi-shot-assault-weapons-of-the-1700s-and-the-2nd-amendment/