Nikon D7100 and sigma 150-600 sport on a manfrotto gimble,this guy said he had sold his Nikon 500 f4 because of the restrictions a prime puts on you doing wildlife meant he wasn't using it enough ?,he said the sigma was not as sharp as the 500 but so long as it was of a high quality getting the picture meant more to him.
Met a very nice couple on a first time visit to the arb. Both had new 810's, plus backups. I got one of the site maps and showed them where some good spots were. He didn't mind a pic, but she demurred.