In the context of the 2nd Amendment, a well regulated militia meant that the members were proficient in the use of their rifles, that they could load and fire a certain amount of rounds within a minute. I believe the number was 3.
If they had the AR back then, I suppose a well regulated member of that militia would be expected to be able to fire off a full magazine, do a mag change, and get back into the fight.
What it didn’t mean was to regulate who could or could not own arms.
There, I trust that cleared that up for you, sonny.