My experience is also somewhat limited, but it has been that Secnars are a pretty frangible bullet on game. I have hit a prairie dog at 1012 yards with a 6mm 105gn Secnar and was very surprised to see a little expansion from the exit wound.
I also shot a fallow buck at 200 yards in the heart/lung area with 6mm 105gn Secnar which stopped the deer in 5 paces. I was very happy with the terminal performance, though the meat loss of the on-side shoulder was fairly substantial.
I will most likely use a Sierra Matchking in preference to the Secnar next time I hunt a game animal.
Fergus