I hunted at Nuanetsi for a big buff this September. I could have shot a 41", but I couldn't keep up with the PH.
During 6 days of hunted we spotted another 41" and one 45", but they were too young in the opinion of my PH (Lin Stanton).
According to my PH, to get a really big buff, you have to get close to a lot of buffalo. Plan on tracking up to 2 or 3 different groups every day that you hunt. In a 10 day hunt, you will have a chance to get a really nice buff, if you can locate 3 - 10 bulls a day. That is a lot of walking and a lot of getting in close.
I wound up with a 36" buff, mainly because my arthritic hip was giving me fits.
Good luck.
BH63
PS Many PHs do not want you to shoot breeding bulls, no matter how big their horns are. Make sure you and the outfitter understand each other before booking the hunt. Having a 40+" buff feeding 30 yards away, but not being able to shoot it can be frustrating.
