question :
what is of importance what well regulated meant 1787 today ?
how is 1787 diffrent from 2016 ?
where ther semi automatic weapons with 20 round exchangeble magazine capable of killing people at 800 meters available 1787 ?
did the founding fathers even imagine these weapons could exist ?
Of course they could image those kinds of weapons could exist. Not only had people been trying to increase ammunition capacity and firing rates since the first firearms were created, some of them had already been in existence long before the Constitution, like the Puckle Gun, a kind of a flintlock Gatling Gun dating back to 1718.
The Continental Congress even went so far as to look into buying the Belton Flintlock, an early machine gun-type weapon that would have fed ammunition in via a belt. They abandoned the project because it was too expensive.