CCI-200s in my 260
CCI-450s in my 223AI (-200s were cratering and occasionally piercing)

I've interchanged -400s, -450s and Rem 6.5s in ARs and not seen any measurable difference in accuracy or ES/SD.

Once I burn through the last couple hundred -400s and Rem 6.5s, I plan on going all -450 for my small rifle primer needs.