Gerrod of GSCustom posted on AR the importance of twist when using monometal expanding bullets. He also stated that was the main reason to drop down a weight from your normal lead core.
I killed an antelope near Medicine Bow, Wy. around 2004/2005 with 180 TSX at 777 yards from my 300 win. The bullet was not recovered, but the internal damage was undistinguishable from animals taken at closer ranges of 100 yards or so. My 30 win sports a 1 in 10 twist.
Not sure the the twist rate on my 416 Rem but I know that it is too slow for 40p grain TSX as they will tumble during penetration and don't open well but, the 350 grain TSX at the same velocity peneyrates straight and expands very well
