I doubt you are going to find anyone else with an 03 Springfield in .223!
The 1/14 barrel will limit you to probably 50 or 55 grain bullet weights at most.
Just pick one out of your load manual and gofer it.
My old 1/14 .222 Rem liked 52 grain Sierra Match HP's real well.
I'd probably try WW-748, or Benchmark, or Varget powder.
rc