What appears to be a vertical crack in shoulder of twice fired Lapua .308 brass. Looks like a crack, but can't feel any physical crack on inside or outside of casing. This occurred on second firing of this brass.
Bolt rifle, AMP annealed after first firing, NT to 14, no other pressure signs, Redding S type with bushing, very small shoulder bump.
Any ideas on why this happened? Just a bad piece of brass?