Even under the type of gun control Sanders advocates (universal background checks, bans on assault weapons), private citizens will still be able to buy and own

Even under the type of gun control Sanders advocates (universal background checks, bans on assault weapons), private citizens will still be able to buy and own firearms. There may well be scenarios where an AR-15 is preferable to a plain hunting rifle, but in the event of an environmental, economic, and societal collapse I think it's unlikely that the kind of gun some random person owns will be a major factor in their survival.