I've shot a fair number of deer size game with Nosler partitions in various calibers and platforms. They have almost universally performed the same way. Complete penetration on classic heart/lung shots. About 15-18" penetration on more oblique shots with bones in the way.
In the few instances where I managed to recover the bullets they all expanded to about 150% of their original diameter and they all universally shed their front core and retained ~60% of their original weight. I don't consider that a failure BTW. Some people will. After all I had to recover the animal to find those bullets!
Having said that, in a 5.56 you simply need as much mass as possible. You really don't want fragmenting bullets. Its not that fragmenting bullets can't kill deer well when they are hit perfectly. They can and will. However hunting will not always present those perfect opportunities and sometime things that appear perfect when the trigger broke go to hell when you hit a branch or the animal takes a half a step etc. So you want a bullet than CAN break shoulders and femurs and keep going.
Deer are not hard to kill at the end of the day.
I don't hunt them with a 5.56 but don't judge you if you do. If I did I'd probably use a solid copper bullet like a Barnes TSX or TTX in the heavier weights (60-80 grains) and I'd keep my shots to under 200 yards particularly if you have a 16" or shorter barrel.
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