Arms, in the context of the Constitution , is thought of as weapons commonly available to the populace at large and consistent with an individual weapon that a soldier might carry into battle. It is also an individual right, at least that is how the writers of the Declaration and the Constitution considered it.
http://languagelog.ldc.upenn.edu/nll/?p=255$this->bbcode_second_pass_quote('', 'A')nother example is the construction of the term to "bear arms" by James Wilson. In the following passage from his Lectures on Law, he equates the passage in the Constitution of the State of Pennsylvania protecting the right "to bear arms in the defence of themselves" with the right of personal defense of one's self or house:
Homicide is enjoined when it is necessary for the defence of one's person or house.
With regard to the first, it is the great natural law of self-preservation, which, as we have seen, cannot be repealed, or superseded, or suspended by any human institution. This law, however, is expressly recognized in the constitution of Pennsylvania. "The right of the citizens to bear arms in the defence of themselves shall not be questioned." This is one of our many renewals of the Saxon regulations. "They were bound," says Mr. Selden, "to keep arms for the preservation of the kingdom, and of their own persons."
Wilson was a signer of the Declaration of Independence, a member of the Committee of Detail, which drafted the Constitution, and one of the six original justices of the Supreme Court, nominated by George Washington. He clearly took the right to "bear arms" to be an individual right.