I've shot deer with them. I've always gotten exits, and soon dead deer. Sierra states they are a light big game bullet.
I've found them adequately accurate from a 1/12" twist Rem M7 .223 (as accurate as it shoots anything). Very accurate from a couple of 1/9" twist AR's. They are very good bullets, but too pricey for shooting varmints and general use. For that, nothing beats a Hornady 55gr bulk soft points, which are now even better as they are boat-tails. I recently got 1,000 for $87 shipped. They kill deer just as well as the 65gr GK at 1/2 the price.