If there is plenty of space left in the cartridge, you should probably try a slower powder. Hodgdon Varget is working good for me. AA 2520 lists as #96 on the powder burn rate table and Varget is #99 so they "should" not be that far apart. But I am shooting a heavier bullet and "needed" a slower powder....

The Varget load is listed as 42-46C gr at 2582 - 2773fps with a 65gr bullet
The fastest load listed is with CFE 223 at 45.4 to 48.3gr and 2649 - 2839 fps

This is on the Hodgdon reloading website which of course does not list other powders...