Exactly. If even 10% of the armed population of the USA decided to seriously resist (and by this I mean, shoot at people) gun confiscation, that's still something like 12-15 million people with around 30 million guns.
The attrition rate for the federal police, as well as any state and local that allowed themselves to be used this way, would be astronomical. Even if they decided to use the military - half of whom probably would rebel at it - it would make the attrition seen in the Middle East look like a Sunday picnic. We've clearly seen how all the fancy hi-tech toys in the world still don't save you from becoming either dead or a wheelchair bound cripple should you face a determined enemy who utilises guerrilla and 4th generation warfare techniques against you.
Last month, I was talking to a guy at my FIL's church, and this guy is really big on that Lindsey Williams guy - some pastor who says that "the elite" tell him all kinds of things in advance about what they're going to do (yeah right, hunh?). Anywise, this guy predicts widespread gun confiscation, so I was like, okay, how are they gonna do it?
He made the argument that, "Well, they'll just roll up in front of your house with a sonic weapon and while you're laying on the floor in the fetal position, they'll just walk in and take them."
Even should such a "sonic weapon" exist, I don't think this would work for very long. It won't take long for the rest of the neighbourhood to start shooting at the "sonic weapons" - and they guys running it.
Situations are not static. Even should FedGov manage to nab a few people using raids, etc., the people WILL adapt to it and find ways to counter it.