Today I was shooting my Pedersoli Hawken .54 rb with a moose milked patch and 85g of 3f behind and a number 11 remington cap on top. After 25 shots on the 26 as the rifle was fired the nipple disentergrated. A small part of the nipple hit me under the glasses on the cheek whilst the rest of the nipple vanished into the ether. After cleaning the rifle I discovered that there was no evidence of the previous nipple and the nipple thread was not damaged, so I simply screwed a new nipple in. Has anyone else how this experience? Any ideas as to what would cause this incident?