Geeze rifle hunter, hope the shoulder healed up. The 458-416 Ruger has been done before. A simple necking up of 416 Ruger brass, and plenty of shoulder to headspace off of. CH4D has also done dies off this wildcat. Likewise, plenty of YOUR shoulder might be saved as well, with no fire forming........

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https://www.africahunting.com/media...d-ruger-long-action-magazine-box.102877/

With so much meat in a 416 Ruger barrel, maybe a simple rebore of the factory barrel?