I would say that there are really two key factors which must be considered together in determining the effectiveness of Armed Resistance:
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[li] The popularity of the resistance. The Anti-War sentiment in America was somewhat high by the time of kent State, so even the people who didn’t approve of the protestor’s actions sympathized with their motivations.[/li]
Contrast that with The Troubles in Ireland. Six counties against the rest of the country? In this instance, the North might have some sympathy for their cause, but are almost universally reviled for their actions.
[li] The political will of the nominal “oppressor”. to use whatever means necessary to quell dissent. Admittedly, there may be an element of desparation in such tactics. The Bolsheviks didn’t really have to worry too much about ruining Russia’s economy, from their POV, while the Tsarists were attempting to hang on to their power base, however threadbare it may have been.[/list=1][/li]
It is interesting to note in point 2 that the great mass of Russians were already used to central authority, and Lenin at least provided a hope to them, and therefore support from them, and thus the acquiesence to the Lenin (and later Stalin) regimes to pogroms and purges.
The plethora of variables makes it difficult to say what would be effective resistance (passive or active) in a hypothetical gun confiscation program. Suffice it to say that extreme violence against rank-and-file police and soldiers would probably be counter-productive.
Select violence against political proponents of gun confiscation may or may not be productive; it may depend more upon the tactics used by the “gun police”.
If Grandma and Grandpa are being dragged from their homes by SWAT teams while armored vehicles patrol the streets…
But more likely, a lone John Nutcase will blow away a team of [insert your city’s name] police going door-to-door with blanket search warrants, and provoke the SWAT teams backed up with light armor, and maybe more.
Rewards may be offered; “turn in your gun nut neighbors for a $1,000 reward” and such to motivate the citizenry by their base impulses.
Unless there was a widespread, simultaneous uprising by every gun owner in America (call it a coordintion factor) to resist the gun police, the little groups of isolated resistance would be crushed like eggs under the treads of tanks, live-and-in-color on the evening news.