Why not just use a "deer rifle". The .223 certainly was not designed for that.
Well, in some parts of the country, a rifle firing .223 Remington cartridges IS a "deer rifle" and is a mighty effective one, particularly when paired with component bullets like TSX and Partitions in .224 that offer controlled expansion.
I was born and raised in California and hunted coastal blacktails there for many, many years. They are not particularly large deer, nor do they require a bunch more killing than the .223 can muster. In the areas where I hunted them, a big blactail would go about 120 on the hoof. If you got presented with a shot farther than 200 yards, that was rare, indeed. In most cases, most of mine were taken at 100 yards or so or less. Sometimes much less.
I started using a Mini-14 for this coastal blacktail hunting in 1988. At the time, I owned a Griffin and Howe Springfield in .30-'06, a Remington M-700 Mountain Rifle in .280, a Ruger No. 1 in .270, and the .30-30 Marlin that my folks bought me when I was 12.
Why didn't I use one of those "deer rifles," instead?
I had used a couple of them to successfully take blacktails before trying the Mini-14. The wimpiest of the lot, the lowly .30-30, made the biggest mess out of the deer I shot with it, making FIST SIZED exit holes through the off-side shoulder. Beleive it or not. I chalk that up to fairly thinly-jacketed bullets used in deference to the round's fairly low velocity. The Springfield didn't screw up the off-side nearly as badly, but I used 180 grain Nosler Partitions in it exclusively. I had also shot one with my S&W M-66 that I carried on duty at one point during my law enforcement career. I shot the buck in the chest at over 50 yards and it was "DRT."
The stainless Ruger would shrug off the salt air and foggy, misty rain of the area where I hunted better than my blued steel rifles. I figured that if the .357 mag revolver could do the deed, the .223 ought to, as well. Plus, we were allowed to use Mini 14s on the department that I served on, provided that we supplied our own and qualified with it quarterly and used department-approved ammo while on duty. So I had been brainwashed to believe that the combo would KILL a fully grown, adult homo sapien wearing heavy clothing at urban combat distances out to 100 yards or more.
18 deer later, along with a host of "ranchland exotica" like Spanish goats, mouflon and barbary sheep, and even feral hogs, have convinced me that with the right bullets, under the right circumstances, guided by the right hands, the .223 isn't just "enough gun" but is in fact the IDEAL gun.
I have taken proabably 30+ head of game with the .223 and have not recovered a single bullet from any of them except for 60 grain Patrition lodged into the off-side gristle plate of a 250 pound feral hog. All have, so far, been one-shot kills. Over half of the animals that I've shot with the .223 have been "DRT" on taking the hit. Those that did keep on moving didn't move far -less than 25 yards or so. I had that happen when packing .30 caliber rifles, too.
No, the .223 wasn't designed as a "deer hunting" cartridge. Neither was the .30-'06.
But deer come in a variety of sizes and are shot under a variety of conditions. For the class of deer we have here around Tahlequah, and the distances I shoot them at, the .223 is more than enough gun, assuming proper bullets are used and accurate shot placement is achieved. The three deer I shot with my .223 last season were one-shot drops, right where they stood, and the bullets achieved through and through penetration. They were 62 grain TSXs impacting at ranges of 55, 135, and 225 yards on deer that weighed in at 120 to 160 pounds on the hoof.
If I ever go hunt mule deer in Utah or do a combined deer/elk hunt in Colorado again, I quite obviously won't be using my little pea shooter. But for the little pint-sized deer we have around here, which are shot at relatively close range, and often from tree stands, the .223 is plenty, in my experience. No, it doesn't make the huge, gaping, off-side wounds that "deer calibers" do, but that is the reason why I like using it. It isn't meat-wrecking overkill on the deer I shoot here at home. It simply does what I want it to do -that is, it kills the size of deer that I use it on in its tracks.
My .30-'06 won't kill them any deader than that.