.585 Ross Seyfried Cartridge ID

I recently acquired a cartridge which I cannot identify. The headstamp reads “585 ROSS SEYFRIED”, however, it is not a .585 Nyati.
Bullet diameter is .619"
Rim diameter is .632"
Base diameter is .655"
Case length is 3.235"
It could be a Nyati based wildcat, but the case length of the Nyati is about 2.8" I believe.
I am looking for an ID on this round.

I’d say it’s the Nyati basic case with a 600 NE bullet seated. It’s possible someone chambered a rifle for it, but I would lean toward a dingbat. Headspacing on the case mouth is not something you generally see with big bore rifles, given the heavy crimp required to keep bullets in place under recoil.

That, of course, doesn’t apply to single shots, but then a rimmed case would make more sense.

If you look about halfway down this page, there appears to be a nearly identical cartridge, but I think their conclusion of “600 rimless NE” is a little tenuous.

I have it as an empty case so I can’t say if the bullet is correct.

Ross Seyfried is (was? I’m not sure if he is still with us) an African big game hunter and writer of some renown.

I seem to recall obtaining my case before the Nyati hit the streets, but I could well be wrong about that.

Sorry not much help.

Ross is still with us. The original Nyati case was a 577 Nitro with the rim turned down and an extractor groove cut. The taper was then blown out, and a small shoulder formed, topped with a .585" bullet. There were a few variations in rim diameter and length, but the basic cases from Bertram were untapered cylinders, which, before forming, are a near perfect fit for a .620" bullet.

Thanks for the discussion on the cartridge. I am beginning to wonder if the cartridge was an earlier experiment by Ross. The cartridge in the forum discussion that Cannon brought up looks extremely similar to this cartridge and has a 3.25 case length. I agree that it isn’t a 600 rimless nitro (the 600 rimless I have has a neck).