What 55 grain bullet? Regardless, in that situation at that distance I'd have head shot it.
With a SAMMI 223 Rem I would suggest using a 62 TSX to put a hole in something important. They expand reliably, retain weight reliably, and will put two holes in a whitetail longways. Which is what you want, energy being meaningless. But despite their inherent capability you'll have to hit something the deer needs to live, like a lung or both or it's heart or some pressure side plumbing. Any part of the CNS system. Or get close enough to any of that to damage it. Miss it and it doesn't matter how much powder you burned to do it.
69 Scenars and 75 Amax also do well against deer, but their length chokes AR mags. There may be some others...52 Amax is a candidate but I haven't put one in a deer yet and haven't heard from anyone who has.
I'm using 55 grain Hornady ballistic tip, I don't have it in front of me to give any specifics. Yeah, hindsight, shoulda taken a head or even neck shot. Thanks for the advice on the ammo.