In the NeoMag speed strip clip there was mention of a .375 revolver and a couple of questions. I've never handled one but here's some info along with the story of the Elgin Gates SuperMag line of cartridges. The .375 part of the article starts on page 3 IIRC.
Stretched Performance: The Story of the SuperMags.
Here's a bit of load data: .375 SuperMag - Seville Load Data