I would recommend that you take this question to 24hourcampfire.com, in their deer hunting section. Tell them the shaman sent you.
There are a lot of good deer hunters over there that have hunted with the 223 REM. It is a perfectly viable deer cartridge. As long as you don't try it out too far and make a good shot, the deer falls over just like every other good deer round.
I've been on 24hourcampfire.com since 2002, and I've seen a huge shift in attitude in 223 REM. 15 years ago, 223 REM on whitetail was considered a stunt. Now, it's pretty much a no-brainer.
I have been threatening to try it myself. I have the rifle and the load, but every year something comes up. I'm turning 60 this year and it's on my list, but I've got so many deer rifle projects open right now, I may be 75 before I get them all fully tested.