The 2nd amendment is not about protecting yourself from common criminals, in fact I would argue the intent of it is for the people to be well armed enough to be the army of the United States should the need arise. The large standing armies we have now were definitely not the intent of the framers.
"The right of the people to keep and bear...arms shall not be infringed. A well regulated militia, composed of the body of the people, trained to arms, is the best and most natural defense of a free country..." (James Madison, I Annals of Congress 434 [June 8, 1789])
"A militia, when properly formed, are in fact the people themselves...and include all men capable of bearing arms." (Richard Henry Lee, Additional Letters from the Federal Farmer (1788) at 169)
"What, Sir, is the use of a militia? It is to prevent the establishment of a standing army, the bane of liberty.... Whenever Governments mean to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise an army upon their ruins." (Rep. Elbridge Gerry of Massachusetts, spoken during floor debate over the Second Amendment [ I Annals of Congress at 750 {August 17, 1789}])
"...to disarm the people - that was the best and most effectual way to enslave them." (George Mason, 3 Elliot, Debates at 380)
"Americans have the right and advantage of being armed - unlike the citizens of other countries whose governments are afraid to trust the people with arms." (James Madison, The Federalist Papers #46 at 243-244)
"Before a standing army can rule, the people must be disarmed; as they are in almost every kingdom of Europe. The supreme power in America cannot enforce unjust laws by the sword; because the whole body of the people are armed, and constitute a force superior to any bands of regular troops that can be, on any pretense, raised in the United States" (Noah Webster in `An Examination into the Leading Principles of the Federal Constitution', 1787, a pamphlet aimed at swaying Pennsylvania toward ratification, in Paul Ford, ed., Pamphlets on the Constitution of the United States, at 56(New York, 1888))
"As civil rulers, not having their duty to the people before them, may attempt to tyrannize, and as the military forces which must be occasionally raised to defend our country, might pervert their power to the injury of their fellow citizens, the people are confirmed by the article in their right to keep and bear their private arms." (Tench Coxe in `Remarks on the First Part of the Amendments to the Federal Constitution' under the Pseudonym `A Pennsylvanian' in the Philadelphia Federal Gazette, June 18, 1789 at 2 col. 1)
etc, etc
