The 585 Nyati is based on the 577 NE 3" round, the rim is rebated, to the same dia as the 505 gibbs, and the case is shortened to 2.8", though there are some 3" varients floating around.
The 577 T-rex is an original case.
The 505 Gibbs is too small in dia to provide a sholder for a rimless .585" round, the 585 Nyati is borderline.
If you are interested, I can e-mail an article on the 585 Nyati.
Regards PC.
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