Starline brass

[CZ527 Guy]

No issues here with upper end,  bolt action loads after 4 firings in my Howa mini or my Pacnor barreled CZ527. Using a mighty armory full length sizing die, in my case.

Looks like you should dispose of your brass, Send the Virgin brass my way

JS1122: Seriously, what rifle system are you using your brass in? Are you working with upper Gas gun loads or Bolt gun loads?

Its a gas gun, and it is a max book load from hornady's gas gun data sheet, but the hornady brass takes thee same load in stride.
my hornady brass is on its 3rd loading with the same load.

Like mentioned here No reason to expect two diffrent manufacturers, Brass to perform exactly the same. More often than not, I am running right at 1 grain below max listed  bolt gun, load in my rifle. If you like send some my way & Ill run a test in a bolt action system.
Any chance you have chronograph data for the Hornady & the Starline brass, loads?