Adam Lanza had a Bushmaster AR-15, a semiautomatic rifle which used a 30 round magazine.
What does a responsible gun owner need one of these weapons for?
For militia duty of course.
Seems to me, then, that we need exactly those kinds of regulations, if we were to keep with the intent of the Amendment.
If you paraphrase the amendment it might say: "The weaponry the citizens possess is none of the government's business."
When the congress adopted the amendment the word 'State' was capitalized. Jefferson was Secretary of State and was charged with preparing the amendment and sending it to the states for ratification by each. He changed 'state' to lower case, and thus changed the meaning that the congress had envisioned, divorcing or separating it from the incorporated State, and thus the government itself. The amendment now protects the 'condition' or 'state of freedom' of the people, not the incorporated 'State'.
We have always considered that the right to bear arms was under the guardianship of our present government system and intended to protect our incorporated territories, the 'states'. Jefferson worded the amendment to be a natural right of a people regardless if they possessed a constitutional government or an incorporated territory.
If everything failed the people at large would freely possess the means to protect and defend themselves. Jefferson believed that if the 'state' failed a well-armed citizenry would quickly restore or maintain order by means of a militia who would assent to regulation and discipline.
This is the true meaning of the 2nd Amendment.