The 2nd Amendment was designed to protect an individual right to keep and bear arms, so that a militia force could always be raised in time of need to fight tyranny foreign or domesic. At the time, people were called to keep a musket, ammo, powder, etc. at hand. Translating that to a modern militia, the weapon would be any small arm, such as an M-16, AK-47, handgun, and so on. The rockets and mortars can be obtained in time of need from a national guard armory... essentially like the Iraqi insurgents did it, and how the Afganistan rebels won out (with US help) against the Soviets.

Oh, good! I didn't realise the 2nd amendment permitted us to keep AK-47s, rockets and mortars. We're safe, then!