Lloyd, the 308 Norma Mag has a longer neck than the 300 Win Mag. Here's some of the history: https://en.wikipedia.org/wiki/.308_Norma_Magnum As it points out, if you have the dies you can form the brass from 300 Win Mag. That's what I did for the first go round back in the 80s. Then I picked up some once fired Norma brass then found some new Norma brass. It all went when I sold the rifle.