I’ll give on #5, .375 Gibbs, it is an obscure cartridge based on Rocky Gibbs’ creations, same shoulder and blown out profile. From what I have found it was an idea he had but I am unsure if he ever built one. This one was done by Dale Storey of DGS, Inc. There is very little information on this out there and almost all you find on the Googler nowadays is the long range, Cheytac based cartridge of the same name.
Great little cartridge with near H&H velocities, formed from 35 Whelen brass.