I've been called a liar for stating that I have personally seen killed (not by me) western diamondbacks of 9 and 10 feet.
16 and 17 inches around - just behind the head.
I'll bet!
But FWIW the one I posted a pic of, though he was an Eastern Diamondback, was 19 inches around, and had three rabbits in him, though you couldn't tell till I skinned him.
I just can't figure out how I hunted these things for 35 years in half a dozen states and I'm the ONLY human on the planet who has never seen a 9 footer!
Course, I find since I started hunting in Texas that I'm the ONLY hunter there who has never killed a #450 hog...