You haven't been doing your homework. History tells us your scenario can be disruptive is but is seldom, if ever effective for overthrowing a totalitarian/authoritarian government. The cost of such scenarios is typically 25+ civilians for each government or military operator. Recommend you review Germany 1930-40's.
legal gunowners...?
You are not paying attention.
FAR more than that will be available with only a tiny fraction of gun owners.