What are you doing to the cases to make them so black? Is there a problem with your AMP. Properly annealed cases should never turn real dark. Are you annealing with traces of lube on them.
I started to not clean my brass based on experience shared by fellow shooters. Previously i used a flame based annealer and recently upgraded to the AMP. in both scenarios, the necks came out dark, especially after sizing and not really sure why. I anneal after firing so there is no lube on them at all.
Your at 25.3??? The max fps in the manual is 100 fps less than you have. Where did you get your max. charge suggested from?
I worked my way up to that load. I have had the mindset from ELR to 1) push heavy bullets fast and 2) fill the case to a minimum of 90% which is what my goal was with the Berger 85.5. My freebore allows me to push the bullet out so i dont have to crush the powder. I get really good performance with this load at 600yds and 800yds. This is the load that my daughter uses to consistently shoot in the mid 580s for FClass with her last local match performance at 589 16x on a home built FTR rifle. My original testing got me to a max of 25.5gr CFE223 but i backed it off a little to 25gr CFE223 and an average MV of 2840. It is a little hot but before this separation problem, there were no other signs of over pressure.
I know Varget would be the perfect powder but was just trying to make the best of the powder i had on hand.