That's a grown timber rattler. A big one is 5 ft. Very bad bite ! I killed one a few weeks ago about 4 ft long on my 4wheeler crossing a trail by my tree stand. Very bad bite... they also call them velvet tails.
Yeah the Timber rattlers and Copperheads we definitely have to watch out for. Years ago at my old home place we had one of our dogs who was walking through the woods with us get bit multiple times on his head by a Copperhead in a thicket. We had to take him to the vet as he couldn’t walk after being bit. He recovered after the vet treated him though. My dad still finds Copperheads occasionally around his house & dog kennels and has to kill them. Thanks for watching!