I know this is most likely a very unpopular topic, but I thought I should share my experience since there isn't much 5.56 SBR info out there.  I had no other option this year except to hunt with a 5.56 SBR.

I was only left with a 5.56 SBR after selling off all my guns due to financial troubles.  It would have been sold too if it didn't take so long to transfer and find a buyer.  I needed 4 to 6 deer to cover what my family eats every year and had only killed one this year before I sold my 6.8 upper.  I have tested 63gr Fusion and 70gr TSX years ago which both have enough velocity to expand past 100 yards out of a 11.5" barrel.  Both have expanded nicely at 100 yards when fired into water, waterlogged phone books and waterlogged Styrofoam (I know this doesn't relate to real world).

I have limited myself to only shots to under 50 yards, broadside only, and aiming for double lung/heart shot while avoiding the heavier shoulder bones.   I am using an 11.5" SBR with 1:7 twist and 63gr Fusion.

First two does were both hit a little forward of mid ribcage and high (climbing stand hunting).  Both had complete pass through with nice exit wound sizes.  One was heart shot and dropped in her tracks when shot at a range of about 40 yards.  The other was shot at about 20 yards out, missed the heart and made it about 10 yards before piling up but left a track-able blood trail.  

The last was a 6 point buck who was a bit heavier and was shot at 40 - 45 yards.  The buck was walking and I hit him couple inches farther back than mid ribcage.  Made a double lung pass through and he ran a little under 50 yards.  Blood was difficult to follow the first 10 yards but picked up a lot after that.  

All rounds broke ribs on both sides and still exited.  All exit wounds were were similar to the size I typically see with a .243 using Remington CoreLoks.  There was more blood trail than I expected.  I think this is all due to using premium bullets and very short ranges.  Although I think this would work out to 100 yards, I don't want to push it and will keep my shots under 50 yards.  I am going to start to carry the camera so I can get pictures and hopefully add them to this thread.  I don't recommend this unless you are dead on steady shot and able to watch deer walk because they are outside of your range.

Fusion fired out of 11.5" barrel at 100 yards into cardboard box lined with a trashbag.  Box was filled with water and shredded cardboard and newspaper.

I have no doubt that with proper bullet construction and placement, that the .223/5.56 is plenty of gun at the right distances.

There's another thread on there that shocked me with Barnes TSX performance on whitetail.

Found it

Sounds to me like you know what you are doing. Let's face it... a .223 will kill Rajid at 200 yds, why not a 140-150 lb. deer, with great bullet placement? There is an old saying..."beware the one-gun man". Had a cousin who guided in Casper Wyoming area from late '49 til mid '80's. He had a literal garage full of mounts from his own hunting and a few of his clients (who were meat hunters) that he shot with a M 99 in .300 Savage with (iirc) 180 gr. Bullets. Only a couple of Moose, and a Caribou took more than one shot. I know this for a fact as I was with him on the Moose hunt. He was a true hunter, long stalks, reading the wind and terrain, just to be able to get within 200yds or less. Generally 100-150yds was his preference. Point being, you can hunt with a M2 .50 bolt action and be lethal to... I don't know, say 1500 yds. Or you can hunt. Get down and dirty, up close and personal with it. I shot a spike buck with a .22WMR in an area where we were squirrel hunting, late in the season, on my own land. 21 yds, right in the ear. Would I do it again, no. Not unless I had to. Unfortunately the reason we have ammo limitations for hunting is mainly due to the small %age of slob hunters who can barely see through the fog of last night's booze up in camp. Or they lack the desire to be truly capable accurate shooters/rifleman. If the man/regulations allow it and you continue your prudence in shot placement and distance restrictions, good hunting. jmtcw...44.

Glad to hear it. I'm down to my 10.5 though I did buy a barrel and bolt in 6.8 for it. I posted a topic like this awhile ago I think the only other person that spoke up was with a 12.5 ak sbr.

Eta: did you go true old school and use irons or did you use an optic?

I have hunted with a 6.8 SBR for years with 11.5 & 12.5 inch barrels and taken dozens of deer out to 125 yards. 6.8 is very capable out of a SBR out to 250 plus yards.  I was getting around 2950 FPS with SSA 85 TSX out of my 6.8 SBR.

I am running a Leupold Mark AR 1.5-4x on the 5.56.

It has brought some challenging fun back into hunting. I have spent a lot of time adjusting my location, following trails and food sources, and reading the signs. I have watched a nice 110 class buck walk past through the thick stuff and passed up several iffy shots where brush was a possible issue. I have had 15 or so deer outside my self imposed 50 yard limit that I had to let walk. With money the way it is this year I might put two or three more in the freezer.

Good to hear you're making due with what you've got and not having to lay out for the season.

I popped two does on Friday with the 6.8 SBR and couldn't be happier with the performance of the round out of such a short barrel. (85 TSX).