I've saw some pictures of the failure today. The case is blown out at the extractor location...the case is still stuck to the front of the bolt. The OP mentions this rifle has a custom extractor. I can't imagine how a custom extractor would cause the failure. Where the case is blown out the brass looks really thin. The thin look to the brass could be due to many things, from the fact it simply looks thin to the fact that being massaged by very high pressure actually made the brass thin. But, the case could have been abnormally thin close to the base and the failure was simply due to a blown out case at the extractor where the case is not supported very well. It was reported to me that the owner uses Norma brass.
