At that range you MAY experience penciling with the 100TSX & 25-06, if you would like to keep this bullet style, I would recommend the 100 TTSX hold on the animals shoulder & BANG....FLOP end of story. The polymer tip will initiate expansion at lower velocity.
There were several recorded events (years ago) regarding the .257 Ferguson (sp) which is similar to the .257 STW pushing the 100TSX @ ~4000fps; anyway there were several recorded instances of the 100TSX showing 100% broadside penetration on BUFFALO (american). So i'm pretty sure it'll make it through the shoulder of North American big game!