I'd still rather have a 168 gr TTSX at 2500 than a 120 at 2400. You'll just have a better reaction and more penetration, and it'll open up better shot opportunities. I took my elk last year with the 130 grain TTSX at 3000 fps from my suppressed 18" .308 M700, but it still took three shots.
I broke his onside shoulder with the first shot dropping him, I put a second shot into the crease where his neck and shoulder meet. The third shot was a finisher as when I got to him as he was still trying to lift his head. I didn't have a single exit except for the finisher, and I did the gutless method so I didn't try to recover the bullets.
While it worked for me, I firmly believe a heavier and slower bullet would have worked better and given greater penetration. I might of had both front shoulders broken if I had used a 168 gr TTSX at 2500 fps. No doubt you can kill an elk with a .300 BLK, but I wasn't all that happy with my results from a light bullet going much faster than you can produce.
