Novice reloader, loading about a year now, i was working on load development for my 7MM RM, was on low end of charge and 1 round developed 3 wrinkles just below case neck, brass was of name brand, this was the 3rd time it had been loaded, i was clocking the rounds and it was in range of the 6 rounds i speed checked, can anyone tell me why only this one case did this.