We could get into another argument over exactly what kind of "arms" are protected by the 2nd Amendment here. Hopefully we can limit this discussion to "portable firearms" and not crew-served weaponry or artillery/RPG type weapons.
I would tend to agree, but even the cannons of the revolution were crew-served.
I'm not sure, that under the theory that this passage illuminates what is protected, that the a SAW (as in M249) wouldn't be protected.
I. for one, would rather see some special requirements on the public owning weapons such as an M249 (such as secure storage requirement, some level of training certification, etc.) than to see them prohibited outright.
I think when we get in to the category of mortars, grenages, shoulder fired rockets, etc, these are probably dangerous and unusual.