Original intent.
The founding fathers did not have RPGs, so they could not have intended for the Second Amendment to apply to RPGs.
They did, however, have fifty-caliber rifles.
The founding fathers also didn't have computers, or Free Republic, so they could not have intended for the First Amendment to apply to the Internet, by your logic.
Here's what one of the founding fathers had to say about the right to arms:
Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birthright of an American... The unlimited power of the sword is not in the hands of either the federal or state government, but, where I trust in God it will ever remain, in the hands of the people.
- Tench Coxe
Pennsylvania Gazette
Feb. 20, 1788
An RPG is most certainly among the terrible implements of the soldier.
Same thing to free speech on the radio even though the founders didn't include radios in their original intent.
They had cannon. And ships mouthing several of them. All privately owned. They intended the second amendment to protect arms, not just rifle, pistols and handgun, but also swords and in the words of one of them "every other terrible implement of the soldier". I think that would cover RPGs.
Congress have no power to disarm the militia. Their swords, and every other terrible implement of the soldier, are the birthright of an American. The unlimited power of the sword, is not in the hands of either the federal or state government, but, where I trust in God it will ever remain, in the hands of the people."
-Tench Coxe
BTW, he said that *before* the second amendment was added to the Constitution to make sure it would continue to be true.