Deer rifles work just fine. Note the success of the WV and DC snipers with weapons of similar firepower.
FYI... when push comes to shove, a hefty percentage of that "most powerful military force" will be on the other side. (I've had many conversation with friends in the service about this.) Besides, even if they do not, 2 million massed soldiers vs 45 million scattered snipers doesn't look much like a losing proposition for the populace. If only 1 in 5 bother to fight, and only 1 in 4 of those manages a hit before they are eliminated, the snipers still win with a million men to spare. Those are decent odds, and the exact logic behind the Second Amendment.
We have gone 'round and 'round about that point on this forum at least a half-dozen times. Your point is valid, and yet, not entirely. I want to say that I do not wish for, nor do I advocate any sort of armed resistance or 'first strike' move on the part of Constitutional Patriots. Nobody will win another Civil War; such a thing would make the first civil war look like a picnic.
The level of destruction and loss of life would destroy the US. And in the end, the current government could not govern because there would be such trauma to the citizenry that no trust and possibly no infrastructure would remain. But it is precisely this horrible scene that allows the unchecked advance of those enemies of freedom in and out of Congress and the courts who correctly surmise that no sane adult would want to jeopardize the life they have built for themselves. They advance virtually unopposed because there is no real Separation of Powers.
Therefore, I have seen the Free Republic converted to a Mutant Socialism over time by legislative action, executive decree and judicial fiat. The sad fact is, there are no firebrands like Patrick Henry, et al, left in America; we all have a "vested interest" in maintaining the "system".