I'm going to answer this, from an opinion standpoint. I'm not sure of the laws regarding medieval weapons....most of which seem far more ******, and of a pain inflicting nature then any firearm I've ever seen....but anyway,
When the Second Amendment was written, The Government, and the common man, were on the same ground. They were supposed to be equal in their ability to mount a fight. In many cases, a wealthier civilian theoretically could buy a better quality ***, then a soldier was issued. In fact, until the Federal Firearms Act, of 1934, any man, with the money could walk into any store that sold them, and buy a Thompson sub-machine ***. I believe that's how the Second Amendment was meant to be, and I still do, regardless of what others think. or the laws that are ******, although I do abide by them, I don't agree, or support them.
Having said that, I would say that any device used to defend, or mount an offensive ****** would be considered an "arm", and if it's what you feel puts you on equal ground with the group of people you feel you would need to arm yourself against, strap one on. However I will tell you this....it's a fuckload easier to pop a 15 round magazine, into a 2 lb, ***, and take cover as you defend from a secure position, then to carry a 50 lb *****, and then have to wield it around in an open theater of engagement.....but you do come from a fucked up country, and you do tend not to pay attention to how really fucked up it is.
So yeah...wear the *****, use it for defense....but the criminal will likely just shoot you, because HE'S A CRIMINAL....AND DOESN'T OBEY THE LAW!!!