It won't be the vegans, the hippies and all the other people the right wing pundits like to paint as enemies who will take up arms when political and social upheaval comes. In the US, most of those people wouldn't even know how to click off the safety, let alone know the difference between a 5.56 and 7.62mm round or what semi-automatic versus a 3 round burst is.
There are however, people anxiously waiting on the sidelines to use their caches against people they dislike. The liberals, the Jews, the Muslims, the intellectuals, immigrants, or union members. Don't believe me, check out sites like Stormfront (if you dare) and any other white supremacy/right fringe/conspiracy site and see the number of people who are just biding their time to open fire. Every once in awhile, one of them jumps the gun and goes off prematurely. No puns intended. Afraid of "jihad"? Have you heard of the people who anticipate the coming of the "RaHoWa (Racial Holy War)"? Those are the people I'm really worried about. Combine that kind of hatred with the militant useful idiot status they hold and that is a true recipe for massive bloodshed. It is only a shame that those people can't be placed on an island with the most militant jihadists while the rest of us get on with our lives.