Can't imagine any problem if you stay within the load parameters. Speer shows a COAL of 3.105" in their data for their 350 gr bullet in the 458 WM.
The nose length- from the front of the last groove to the nose for the 450 Barnes TSX is .86" so adding that to a trim length of the WM of 2.490" = a COAL of 3.35" which us just .01" over the listed max for the WM of 3.34". Unless something is too "tight" in your rifle that is plenty close enough so it should work fine for length. Most 458 WMs have a long throat and .01" shouldn't matter at all for magazine clearance or feeding.
