Usually caribou are not even half of 600-700 lbs, and are much less tough to kill than elk, for example.
Alaskans can take caribou for ‘subsistence’ and historically have frequently used cheap military surplus rounds.
I load 29 grains H322 with 110 TTSX and my chrono says 2800 in my 6.8 stag. Thats plenty to drop almost every caribou or blk bear you'll ever see.