I'll bite.
Trapper, since you'll be using a 223, I would move for about 3" behind the elbow of the deers front leg. The 223 is way too light to try punching through a leg bone. Three inches behind will keep you well into the vitals.
As mentioned earlier here shot placement is everything, so I'd suggest you get the 223, load it with a bullet designed for medium game, like a Nosler Partition or comperable, and practice. I do not mean 10 rounds at a paper target from a bench. More to the tune of several hundred rounds from sitting on the ground, prone, with rifle over backpack, etc. even practice standing shots. If you cannot keep your shots within a 5" circle at whatever position and yardage you are shooting, you should not shoot at a deer under those conditions. Ie, if you can only hit a 5" circle from standing position at 80yds, but spreads out to 7" at 120yds, then do not shoot a deer, while you are standing, from farther than 80yds.
You owe it to the animal.
You'll be much more accurate from sitting or prone so expect the range to open a bit in those positions.
Listen to the advice of those on this forum for a bullet to use in the 223. The 22-250 is a whole different animal cause it has a huge velocity jump on the 223, even though it shoots the same size bullet.
Several companies make bullets that will work, just make sure you do your part and they will do theirs.