Absolutely you can kill deer with FMJ bullets. A lot of the guys I hunted with SC used their high power match ARs with Berger bullets.
There's a big differrence between a Berger and a FMJ though. Walt Berger tested his match bullets on a wide variety of game and found that they almost unerringly penetrate about 4" intact, then very violently expand- traits that would make for a very good hunting bullet.