A well-regulated militia was seen as a bullwark against the establishment of a standing army (large military apparatus).You have to remember the Tory quip about the War for Independence that they would rather be ruled by "one tyrant who was 3000 miles away than 3000 tyrants a mile away".
The founders were well aware of ancient history (Roman and Greek) and knew that tyrants wanted a large military.
In the exact sense, a tyrant is an individual who arrogates to himself the royal authority without having a right to it. This is how the Greeks understood the word 'tyrant': they applied it indifferently to good and bad princes whose authority was not legitimate. [Rousseau, "The Social Contract"]
IOW, if "Chief" Kessler wants to kill tyrants, then the next time he needs to make sure it's lethal shoots himself.
Also, don't forget that tyrrants can usurp power, which is why the militia is "well-regulated"--that is under civilian control (and the Domestic Violence Clause exists). The entire standing army v. militia debate was about how much control would there be over the military. And makes it far more likely that the Second Amendment was intended on addressing the militia, not private arms, since the US Constitution says it is intended to address the common defence.
Let's put it this way, there is far more evidence that the Second Amendment was intended to protect the "Well-regulated Militia" than private arms.