What powder are you loading? Are you with specs for that round?
Doesn't look over pressure to me. Flatted primers would not have that bevel on the outside of the primer pocket.
Each different manufacturer has different hardness of brass. Google the chart that's floating around the internet.
I reload on a Dillon 550, doing each round individually so that I can feel the neck tension when seating the bullet. If loaded correctly, and not to maximum, the brass will last a long time. Case neck splitting from over working the brass is my signal to toss out the brass.
Larger flash hole could cause initial overpressure, since it will ignite the powder intensely, working like a magnum primer.