Do the remains look something like this?
There have been several threads on Trapshooters.com discussing blow ups recently. I don't recall Rottweil being mentioned, but it would be extraordinary if reloads were not involved.
Shotgun Blowups
http://www.trapshooters.com/threads/shotgun-blowups.244114/ Smokeless Powder DDT
http://www.trapshooters.com/threads/smokeless-powder-ddt.245629/ Unfortunately, the various interlocutors, including myself, are only expressing opinions and to my knowledge there have been no published results of a failure analysis or metallurgical study. Guns sent to the manufacturer tend to disappear without a follow-up report.
