I would agree with the others in that I too feel the .223, especially out of a Handgun Length barrel is marginal at best for Deer sized critters. Shop around on the various classifieds and or ebay to get a more suitable cartridge. In addition as has been stated the .223 is not legal to harvest deer in many states.
Now if you would have asked "Can a .223 14" Contender KILL a Deer", I would have to answer YES. Here's the situation. A buddy and I were done Deer Hunting (all of our tags were filled), and we were heading out for an afternoon of predator calling. My buddy had a Smith & Wesson Model 1500 Rifle in .223 Remington and I had a Super 14 T/C Contender in .223 Remington. As we were driving down the road enroute to our hunting spot a couple of hunters flagged us down.
Seems these guys had wounded a nice 4x4 Whitetail Buck and were unable to finish it off as they were now out of ammo. The Buck was standing in a small patch of weeds and looking sick but still on it's feet. These guys asked if we had a gun and could we shoot their buck to finish it off.
Well I said YEP WE CAN, and I got out of the pickup with my Super 14 .223 Contender. I flipped the legs of the bipod down and rested the Contender on the hood of my buddies pickup. I could hear the guys questioning my buddy, "He isn't going to try to shoot our Buck with THAT THING is he".
About that time I had the crosshairs of the 7x Burris Handgun Scope centered on the Bucks Chest as it faced me. I continued pressure on the 2 pound trigger and at the shot the Buck sat on it's rump, stayed in that position for a second or two and simply fell over. Those two guys were amazed, and then confessed that they had each shot 5 rounds at the Buck after they had wounded it and never hit it.
As luck would have it these guys didn't have a knife either and we had to field dress the Buck for them. As I said this was lucky as I was able to recover my bullet. Seems I had hit slightly to the left of the brest bone and the bullet traveled through the Buck lengthwise and came to rest in front of the left hip bone in a picture book perfect mushroom. I was totally amazed at the bullet performance, eepecially since I was shooting Black Hills Shooters Ammo loaded with 55gr. Hornady SX Bullets.
This was about a 100 yard shot, this Contender was super accurate with that ammo, I had a perfect rest and total confidence in how I could place the bullet. Could I have done the same under a HUNTING CONDITION, well I wouldn't have tried it to find out.
I think the .223 in a Contender Handgun is a great cartridge when used for what it was intended to be used for. I have shot literally thousands of rounds of various .223 Ammo through Contender Handguns over the years in the Prairie Dog Towns of my native South Dakota. For this purpose, and even for Coyotes the .223 is one of my favorite Handgun Cartridges, but for Whitetail Deer or Pronghorns I much prefer something with a little more horsepower.
So if you want to know if your .223 will KILL A DEER I would have to answer YES under ideal circumstances. If you are asking is the .223 Remington in a Contender a Deer Hunting Cartridge I would have to answer NO.
Please don't take offense, but that is my experience and feelings on the matter.There are a lot of much better cartridges chambered in the Contender for the Hunting of Whitetail Deer.
Larry