I used the 215 SGK for some time in my 338 Win Mag. I think I hunted about 50 animals with them including springbok, gemsbok, blue wildebeest, black wildebeest and kudu. I had one not open on an oryx (gemsbok). The bullet went trough the head (culling) and impact velocity was around 2450 fps. Found the bullet in the spine where it entered the animal again and it looked like a hollow point version of the bullet. Think I could probably have loaded and shot it again
Sierra said the impact velocity was too slow for that bulllet although the other animals were shot at similar distance. I did stop using that bullet after it not expanding as it would have been very problematic of it was for instance a lung shot. I am now using 250gr Berger elite hunters and 225 TTSx in my 338 Win Mags. Both produce regular sub 1/2" groups and perform well on game. I got the elite hunters to shoot with various jumps from almost 5mm to almost touching the lands. The G7 BC on the elite hunters is around .351 which is almost as good as it gets when you would like to shoot long range as well.
Sorry for going off topic but I have about $1200 worth of 338 bullets lying around as I tested just about any 338 bullet there was and these two were by far the most consistent of all the bullets I tried. The ttsx was the easiest of all to shoot with various charges.