Okay. I agree on the annealing, but there is a difference in the overall length. Take a look at the SAAMI diagrams. Likewise this will affect headspace.
"....but there is a difference in the overall length." Length of what? Shell case? Chamber? Cartridge Over All Length? I would ask that you be specific, but that would probably just result in more misinformation from you.
> "Take a look at the SAAMI diagrams." I am looking at both the .223 SAAMI Cartridge and Chamber drawing and Army Drawing No. 9378276 for 5.56mm Case in front of me as I write. The SAAMI Case Length is 1.760-0.020". The Army Case Length is 1.76-0.01". They are nominally identical although the Army has tighter tolerances.
You will not prevail when trying to B.S. an ammunition expert. "Likewise this will affect headspace." Wrong once again! The headspaces are identical and nothing discussed on this thread about interchangeability relates to headspace.
Please quite posting misinformation on this forum.
And, when you find yourself in a hole, it is best to stop digging.