For the experiment they had all the measurements and distances, detailed ballistic dummies (with bones and whatnot), positioned properly (the Governor was on a smaller, lower jump seat, and sitting below the President), and they shot from a tower.
They had the same rifle, though not the actual rifle, and they had period ammunition from the same lot that Oswald used. Who knows where they dug that up. I also can’t speak to the atmospheric conditions but those would affect accuracy, not impact.
Only thing hey didn’t mimic was the actual motion. It was a stationary shot.
Sorry to be graphic here, but as I recall this was the shot that hit The President in the throat, passed through him and continued on to hit the Governor, twice, I believe. Through his arm and into his leg.
And you know what?
They did it. They replicated the shot. Was it 100%? No. But I’d call it 90+%.
The damage to the dummies was very similar, including deflection off the bones. They recovered the bullet and it was not perfect, but it was in very good shape. It was simple ball ammunition and did not expand like modern bullets can.
It was, to me, a very convincing demonstration about how little magic was in the original bullet.