Too small for deer. You have less energy than a 223, which is not well suited for deer anyway. Plus it's in a pistol, meaning you better be D@@n good, or your just going to wound medium sized game. It may be a fun small game gun. I actually carry mine as a backup to my 223 when I coyote hunt.
I love my 5.7, but I would never take it into the woods and expect to drag home a deer.
And people that would say that a 22 mag makes a good deer rifle, are also using just that ---A RIFLE.