The argument I always hear revolves around self defense; why shouldn't it be tied to the fact that the 2A specifically mentions service in a militia. Militia members would be at a significant disadvantage having to constantly reload as opposed to government soldiers or police. If police officers need more than 10 rounds just to keep the peace there is no way a militia should be so restricted.

30 rounds EACH. x 6 in the front, one in a speed grab location, and one in the rifle, = 240 rounds of FREEDOM.

EDIT: And that's BEFORE you get to the sidearm.