in the founders time there were three classes of weapons
arms , artillery and ordnance. arms were just that-individual weapons that a regular infantryman or militia man would carry. swords, dirks, daggers, sabers, muskets, pistols and rifles. Artillery were mortars and cannon, and ordnance were bombs and rockets (remember "the rockets' red glare"?). the second dealt with the arms.
now modern weaponry often blurs the lines. a submachine gun is an arm while a crew served heavy mg is more akin to artillery. a mortar is artillery but a grenade launcher attached to a marine's M4 carbine has elements of both. same with an RPG or a SA-7 surface to air missile though I note that normally grenade launchers and missiles are issued to squads or platoons to be carried by a selected soldier while the M16 or M4 rifles are issued to just about every combatant.
so when we come to weapons capable of being deployed by one soldier even if issued at squad or platoon level (as opposed to every infantryman) there is a gray area when it comes to the second amendment. and I will concede that when it comes to RPGs, Strelas, or LAWS, MAWS or HAWS there is no quick answer.
but right now, there are clear and obvious infringements on the second amendement by the federal government that do not require an examination of the RPG issue. for example, many weapons that civilian police departments use--ie weapons that the federal and state government have conceded are useful for self defense in urban environments and clearly protected by the second-that other civilians cannot buy without all sorts of red tape and in fact are often banned
in 1986- in an attempt to derail the McClure-Volker firearms owner protection act (that would prevent Boston POlice from say arresting the Yale Skeet team as it travels through that city to the Eastern Collegiate clay target championships in Nashua NH), Dem Rep Hughes of NJ tried to poison the bill by attaching an amendment that many though was never properly ratified that banned the sale to civilians of all machine guns registered by their makers after May 19, 1986. this of course meant that the number of machine guns for non LEO ownership was cut off and the prices skyrocketed to the point that a gun police can buy for 900 dollars would cost me over 22,000 dollars
BTW to say we would need heavy weapons to deal with a tyrannical government is specious. in such a scenario, the proper response is not to go head to head with the us military (assuming that the army would attack large numbers of civilians and say carpet bomb Columbus or Dallas). rather the response would be to target those who had caused the oppression and take them out. If someone can get within a half mile of someone they can kill them and if you are a dictator and 20 million pissed off american patriots want you dead, you are pretty much toast