> Because "tyranny will never come to America..."

If I'm not mistaken, the implication here is that tyranny might come to America, and I 100% agree with that. Of course it might, and in fact I think the increasing surveillance state atmosphere makes it seem increasingly likely.

But any implication that civilian gun ownership could make a difference if it happens seems overly hopeful. The US military is the largest in the world by a large margin. If tyranny comes to America then a few civilian shotguns aren't going to help much.

You're making the common assumption that such a situation would be "the standing US military roughly as it exists now" vs "rebel citizens with only small arms". This scenario is unlikely to ever happen.

What would be more likely to happen is something like the Civil War where the army itself was also divided. Even more importantly, it is a lot harder to control an army when the targets are the people the army supposedly exists to protect. In a survey[1] of "300 U.S. Marine Corps soldiers" about unit cohesion when working with the UN, the final question asked:

    46. The U.S. government declares a ban on the possession, sale,
        transportation, and transfer of all non-sporting firearms. A thirty
        (30) day amnesty period is permitted for these firearms to be
        turned over to the local authorities. A the end of this period, a
        number of citizen groups refuse to turn over their firearms.
        Consider the following statement:

        I would fire upon U.S. citizens who refuse or resist confiscation of
        firearms banned by the U.S. government.

      (__)               (__)      (__)        (__)           (__)
    Strongly disagree   Disagree   Agree   Strongly agree   No opinion

The results of that question suggests a "citizens vs army" scenario is very unlikely.

          The results [...] with 88.0 percent responding,
    revealed that 61.66 percent said they would refuse to fire on U.S. citizens,
    whereas 26.34 percent indicated they would fire. This particular question,
    unlike the others, elicited form 15.97 percent of the respondents with an
    opinion, either heavier pen or pencil marks on their response or written
    comments in the margin space. [...] The responses to this scenario
    suggests that a complete unit breakdown could occur in a unit tasked to
    execute this mission.

Small groups of people often have some kind of consistency across the group, because the definition of the group self-selects for something. (e.g. the people who choose to attend a chess club tend to like to play chess) As a group grows in size, the makeup of the group tends to become more heterogeneous. Eventually, as the group becomes very large, the makeup of the group tends to resemble the makeup of the general population.

The military is a very large group of people, so the individual attitudes and politics of a soldier tends to resemble the attitudes and politics seen in the country in general. When considering a topic that is obviously politically controversial, you should expect that the people serving in the armed forces will be approximately as divided as the rest of the citizens.

[1] http://www.dtic.mil/dtic/tr/fulltext/u2/a293790.pdf

Thanks, I hadn't seen that survey before.

Your scenario would still present a situation where civilian arms ownership, while the cause of the conflict, is relatively inconsequential in the ensuing conflict itself. The military against itself is still a conflict with military grade arms.

That is possible. My point is mainly that it isn't going to be the lopsided "civilians vs army" scenario. The military isn't a single monolithic entity.

As for the utility of civilian being armed, I think you are underestimating the deterrence factor. Yes, they would lose in some situations and are less important in others.

Consider the situation from the perspective of the attacking army. Fighting an army is hard enough, but that attack is a lot harder if you also have to defend against the population in general. The counter to that problem is a scorched earth policy that doesn't leave a population that could be a threat, but such a policy is risky and can easily turn more people against you.

We see this when our army fights in the middle east: when you want to maintain good PR instead of razing cities, small arms and IEDs can be surprisingly effective.