A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
Translation: In order for an independent free state to securely exist, the state must control a well regulated militia for defense.
Thus for the people to remain free of state tyranny, the people must be able to keep and bear arms in the event of said tyranny.
Not quite, more like- "Because having defense forces that can be ready at a moment's notice is necessary to protect a free state, the right of the citizens to own and carry weapons shall not be infringed."
ALL gun laws are an INFRINGEMENT. The entire purpose of the 2nd as stated is for citizens to be as well armed or more well armed than any hypothetical enemy invading force! I don't know of any invading forces that will use only semi automatic weapons with barrels that must be 16" or longer!