Rthe feral gangs won’t last long. I suspect that there are more guns in the gun free cities than you think.
Problem with a machinegun is toting around all that ammo ~ it's OK if you have a regular source of supply but on a permanent basis it's just not a good idea.
However, those same guys have more than enough superior firepower in single shot and semi-automatic weapons light enough for an average adult to use.
More than enough, and they'd appreciate the company ~ when you're in a foreign country and the SFI you really need a friend who knows the lay of the land and doesn't have a foreign accent.