Neck the 338 Lapua down to 7mm and you have the center round below. Blow that round out to the Allen Magnum configuration and you have the rounds on each side. Try to size the 338 Lapua down to 7mm RM and you will be bitterly disappointed. Check the case dimensions in the photos above.
By the time I got around to checking case deminsions, I could not locate the info I found. When I compared deminsions I couldn't see how it would work either. I thought I would ask and maybe find answers from some that knows more about reforming than I do.