The .585 Nyati (pronounced n-ya-te) is a large-caliber hunting cartridge developed in the early 1990s by writer and professional hunter Ross Seyfried.
The .585 Nyati was originally designed in 1990 by Ross Seyfried as a wildcat cartridge in order to offer the power of the .577 Nitro Express in a bolt-action rifle for a fraction of the cost of expensive double rifles. Seyfried had such a rifle constructed on a Winchester Model 70 action built by gunsmith Franz Bryner of Ogden, Utah.
The .585 Nyati is a bottlenecked cartridge with a rebated rim, based on the casing of the .577 Nitro Express, which was blown out straight to allow formation of enough of a shoulder for headspace purposes.
The rebated rim is so that rifles with a 0.700" bolt body diameter can be fitted for the cartridge.
There are three variations of the case. The first two are a 2.8" and 3" version, both with the same 0.640" rim, and the third is a 3" case with a 0.590" rim (similar to that of the .416 Rigby) to avoid the use of an expensive action with a bolt body diameter greater than 0.700".
Being based on the .577 Nitro Express case, which was designed for use in double rifles, brass formed by this method during the development phase had a relatively weak case head. In bolt-action rifles, a portion of the case head is unsupported and requires more strength in that area.
The casing variation with the 0.590" rim, which is severely rebated, could not feed reliably.
Another issue with the .585 Nyati is that many barrels are being manufactured with excessively tight chamber necks. Seyfried believed that this is due to an error in original drawings for the cartridge. If one receives a barrel with a tight chamber neck, they could ream it out to 0.614" using a neck reamer, so that tight necks and dangerous pressures would not be an issue.
Brass for .585 Nyati tend to have inconsistent quality or be in short supply.
The recoil forces generated by the cartridge is known to be violent and surprising.
Rifles chambered for the .585 Nyati, which are strictly a custom affair, should weigh 11 to 13 pounds (4.98 to 5.89 kilograms) in order to make them controllable.
It was used as the parent cartridge for the .585 Gehringer.
- The cartridge's name means "cape buffalo" in many African languages, especially Swahili.