This is for Avatar (and anyone else who is still interested in the whole bullet-blowing-away-a-person thing):
Okay, I finally caught that episode again and furiously scribbled down notes as I was watching.
First, I was wrong about the dummy used. Initially, they actually used a 180 lb. pig carcass. They built a rack and suspended the pig in it, but in such a way that the pig was finely balanced on its perch, so that any jostling movement would make the pig drop.
They shot the pig carcass at a range of 22 feet, which apparently is a distance that accounts for 70% of fatal shootings.
The weapons used were overseen by the chief firearms instructor of the San Francisco Police Dept. According to him, these are firearms found in most police arsenals.
First he fired an M4 using 9mm hollow point bullets: no movement from the pig. Then a Thomson submachine gun using .45 calibre bullets: still no movement. Then he went to a .44 Magnum with 240-grain bullets (the same calibre Dirty Harry uses) travelling at 1300 ft. per second: no movement. Then he went to an M16 (the one Rambo uses): no movement. Then they had three people fire their M16's continuously at the target: the pig still did not drop.
After a couple more different weapons (whose makes weren't specified), the police officer resorted to a massive deer slug fired from a shotgun. The pig finally dropped, but upon looking at the high speed footage of the shot, the Mythbusters did not think it was the bullet that directly caused the fall; rather, the bullet struck the hipbone of the pig, which caused the legs to splay, making the pig sufficiently unstable that it fell. But it was not blown backward.
Upon inspecting the pig carcass, they saw that a number of the bullets had passed through and had expended most of their energy in the hillside behind the target.
At this point, they took away the pig and put in their test dummy Buster and had him outfitted with a bullet-proof vest. This would force any bullets hitting him to expend all their energy on him instead of passing through.
The officer fired a 12-gauge shotgun at Buster. Buster fell, but he simply dropped down, like the pig, and was not blown backward. The Mythbusters felt that Buster moved maybe a couple of inches at best.
The officer agreed that the myth was busted, and indeed invoked Newton's Law that any action must have an equal and opposite reaction. If you could truly blow a person backward ten feet, then you yourself would be blown backward ten feet. And that would require one truly massive gun in the first place, far bigger than anything even Rambo could carry, heh.
