NoirFan said:
Any quiet caliber that comes in a small concealable pistol, like a 22LR. In a modern armed rebellion that pickup truck full of AR15-armed yahoos won't even get all the way out of the garage before it gets zapped by an aerial drone, or informed on by their neighbors. The only effective shooting that our hypothetical patriotic freedom fighters would be doing is executing and intimidating soft targets like civilian collaborators and the families of soldiers at close range.
Anyway, the resistance movements in Iraq and Afghanistan have shown us that small arms are kid stuff. If you really wish to harm the government and your fellow Americans, stock up on fertilizer, bomb components and discreet torture implements like pliers, car batteries, etc.
Well, small arms are definitely not the most effective against OUR troops in Afghanistan, but our guys are just a small part of the picture when it comes to the power dynamic in that country. The Taliban's small arms are plenty effective against the Afghan police and security forces, who take the majority of the casualties. Once we secure a region, it is up to them to keep it under control. Remember, the EASIEST job of the 1st-world counter-insurgent is winning on the battlefield... the hardest thing for them to do is to install an effective government to maintain long-term control. The insurgent doesn't have to directly engage the combat troops... he just has to wait until they leave and stick it to the police that are left behind to maintain order, who are generally much softer targets. Hence the frequent reports of Afghan police outposts being overrun in rural areas, and why the Taliban is in control of large parts of the country despite an 11 year military campaign against them by the world's most powerful military and its allies. All this in a country smaller than the State of Texas.
It would be a similar situation if an insurgency situation were to take place here in the 'States,
a la a 2A situation. Many people have the notion that it would come down to going toe to toe with the military. That is not likely to be the case for the majority of the fighting. The fact is, there will not be a squadron of Apaches and a detachment of Bradleys in every little podunk town across the country (or even across a disrupted region of the country). Every country which has tried to install a police state over it's own people always relies mostly on, well, the POLICE to deal with domestic resistance. If you want an idea of what the State's forces might look like in a potential 2A situation, look no further than your local law enforcement agencies. Also consider the historical fact that most domestic police states are accompanied by a strongly interventionist foreign policy... meaning that the majority of the military's seasoned troops are committed to foreign theatres.
Having said all that, you are definitely onto something regarding the benefits of small and easily concealable weapons. If you are playing the insurgent, assassination is definitely one way to leverage your strengths and disrupt the enemy's attempts to effectively govern occupied territory. There is a great book called "The Squad," about Michael Collins' IRA hit squad and how effective it was in disrupting British law enforcement in Ireland in the 1920s. Highly recommended for anyone interested in the study of resistance movements.
Handguns have obvious benefits for this role, but so do small/folding stock rifles. I think the SBR has a strong 2A role to fill, along with the more commonly mentioned carbines, battle rifles, and long range precision rifles.
As for you who say that the majority of the armed state employees wouldn't go along with tyrannical orders, I think you underestimate the effects of group dynamics, the ease of demonizing an enemy (even a domestic one), and of how easy it is to come up with an emergency sufficient to justify drastic measures in the minds of many. I'm sure there are a lot of people in a lot of other countries who never could have imagined their own countrymen doing the kinds of things to them that they did. That is all I will say on that matter, in the interest of keeping this thread from drifting way too far afield.
Good stuff guys... keep it coming.