Although I agree that its not an essential liberty, many would say that's debatable. I think using Franklin's quote in the attempt to convey a right to firearms is taking it out of context. I'm pretty sure that what he meant by essential liberties are the three major philosohpical driving factors into the foundation of the United States; that is the right to life, liberty, and the persuit of happiness. Which mainly constitutes a freedom of thought, conversation, expression, life, and that no man should be disquieted or called in question for differences of opinion.

I don't think a right to own a firearm designed exclusively for the purpose of efficient killing of other human beings would fall under the realm of said essential liberties. That is why we see bannings of automatic weapons, military weapons, military grade explosives, and weapons out of the realm of arms designed for the purpose of hunting an animal.

Although one may, like I, argue that the founding fathers' purpose of right to bare arms is to be readily available to overthrow a government which is an enemy to the United States. And thus the lines in the constitution, in the second amendment, of right to organized militia. And therefore an essential liberty might constitute the ability to effectively overthrow a regime which violates the constitution. And therefore it that context it could be considered essential. Although I don't think Franklin's words were used in that context. Although I could be wrong.