I don't see why 600+ yards would matter much, but could see how advances in armor at closer ranges might necessitate evolution in ammunition.
600+ yard engagements were common in Afghanistan and that’s a big driver of the new weapon.
600 yards was common with light infantry rifles? (I'm not saying they weren't, just having a hard time imagining it, partly because past 300 yards my eyes quickly morph into Mr. Magoo mode.)
