Beadman, I think someone is telling you a story. That picture is 4 years old and shows up every now and then on the internet. Check out that link I posted. Or do a google image search for giant rattlesnake. It's in the first row of pictures.
I copied and pasted this from that article: (the Pat B. mentioned is not our Pat B)
The latest picture to be doing the rounds was brought to my attention by a comment left by by Amy R on this blog. She notes that the snake on the right was allegedly killed in Mississippi. Then, Pat B. sent me an e-mail and told me the story takes place outside Baton Rouge, Louisiana. Both said they heard the snake was eight and a half feet (2.6 meters) long (Amy R. also noted the snake allegedly had 21 rattles).
Where do we start? I'll start by saying that those lengths are bogus and the locations are...unlikely.
The snake in the picture is an Eastern Diamondback Rattlesnake, Crotalus adamanteus. This is apparent because of the black and gold diamond-patterning and, of course, the rattle. This species does not reach eight and a half feet long. That would be the world's largest rattlesnake ever known to science. I don't believe this is the world's largest rattlesnake ever known because it is clearly an animal that is approximately half that size and thrust toward the camera on a long piece of wood. It's a rattlesnake camera trick I explain several times above and below.