Pierced Primer

[promethean_spark]

According to quickload, your charge shouldn't be overpressure even if it were pushing two of those bullets. A double charge would definitely be overpressure though, and it would fit since you're only filling to 50.6% of capacity. However, in that case I'd expect to see some squashing of the brass as well as the primer. Check the flash hole and that a large pistol primer didn't get mixed in somehow. If it was a large pistol primer, it will have started out 0.008 shorter, and probably got smashed a bit shorter still.