David: No way. If there's one thing the .223
doesn't need when you're hunting medium game like deer, it's pre-fragmented bullets. One of the main issues with hunting deer, and one of the main shortcomings of many of the existing .223 bullets, is penetration. Super expansion and total energy transfer sometimes makes for some spectacular kills, but if you hit a rib wrong or hit the shoulder just so, you've got one running. I've seen this on an almost tragic occasion where a friend of one of the owners of the ranch I was hunting on shot a north Texas doe (120 lb) with a .220 Swift with 45g varminter bullet moving at about 4000 fps. An *enormous* hole opened on her shoulder, and she took off, hell-bent-for leather. My friend ended up making a very lucky shot at 200yards (offhand) with his '06 to solve the problem.
With a heavily-constructed bullet, at reasonable ranges (sub-150), with a very accurate rifle and by a shooter who knows he pulling a bit of a stunt, I'd say, sure, the .223 will do it. But with all the other rifles out there that will do it better, why would you want to?
Also keep in mind that there are shots that you simply must not take with a .223 on any deer that you would or could do with even a .243. You mustn't take ANY running shots, nor even moving shots. You mustn't take any quartering shots (penetration!). You mustn't take any shots from behind, unless you have a very close (sub-85 yd) head/neck shot (which I don't advocate, but that's another thread...
). And remember that, although you're in an are where a 125 lb deer is big, sure as you take out that little .223, you're going to spy the local record-holder MONSTER 175 lb 150pt B&C at 175 yards. And you're going to wonder if your rifle is enough.
The last thought through your mind as you squeeze the trigger should not be a question of confidence in your gear. This does not contribute to success.
Last year, I was in the Hill country on a high butte, and wanted some range, so I had my Sendero in .300 Win Mag,
clearly too much for anything that walks in Texas. My alternative could have been a .243, or a .223, for that matter, for the two doe I'd already shot. Then, right at dusk, just as I was about to quit for the evening, out steps a humongous 200 lb buck at 150 yards. Of course, there was no doubt in my mind that the buck was mine as soon as he cleared the brush. Yes, I was overgunned, but at dusk, when tracking is going to be difficult, you don't want to be marginal.