grymster2007: Do you mean they are not quick when it's cold out, or always?
It was hot out when I had to rile up that rattler. I would guess it was 3 1/2 - 4 feet long and pretty thick. It tried to strike me, but it never tried advancing. I don't think they can strike more than about a third of their body length and that seemed to be the case. I've never seen on TV or elsewhere, a rattler that could cover ground at more than a couple mph.
100mph strike speed? That'd be nearly 150fps... I'm very skeptical! I doubt they could do more than 1/10 that.
Mr. Snake Charmer - bring on the Cobras!