A friend of mine has a circa 1919 Rigby .470 that he blew up a few months ago on a buffalo hunt. A strip of metal he described as 10-12 inches long and 1/4-1/2 inch wide blew out the side of the barrel. They never found it. The guy standing next to him was dazed from the blast.

Dunno who he took it to for repair in the UK, but he was told that monolithic solids in an old barrel were to blame. He had mix of Federal and Kynoch, and does not know which he fired. However, both use Woodleighs.