Big Bore Compendium – .585 Nyati

18The .585 Nyati was designed by writer and professional hunter Ross Seyfried in order to offer the power of the .577 Nitro Express cartridge in an affordable bolt action rifle. At the time when Mr. Seyfried designed the cartridge, double rifles were out of the financial reach of most professional hunters and client hunters alike, so the concept of bringing the tremendous stopping power of the 577 Nitro Express to a bolt action rifle had great allure. Today one of the most affordable double rifle makers is B. Searcy & Co.of Boron, California, but even there a 577 Nitro Express double will cost US$15,000 at the time of this writing. In contrast, a well-planned low grade .585 Nyati bolt gun can be put together for only US$3000. The author had such a rifle constructed on a Winchester model 70 action built by gunsmith Franz Bryner of Ogden, Utah.

The disadvantage of the .585 Nyati is its use of a rebated rim so that rifles with a 0.700″ bolt body diameter can be fitted for the cartridge. It can be difficult to get a rifle using a cartridge with a rebated rim to feed reliably (see discussion of 500 Jeffery above), so a project for this cartridge should only be undertaken by a master big bore specialist, or by someone who is willing to experiment and throw away the action if unsuccessful.

The standard .585 Nyati uses a 0.640″ rim and has a case length of 2.800″. Another variation uses the same rim but a 3.00 inch length case. With its greater powder capacity, the 3 inch version can push a 750 grain bullet even faster than the 2500 feet per second achievable by the 2.8 inch version, but to what useful end the author cannot imagine. A third variation uses a 0.590″ rim (same as the 416 Rigby) to avoid the use of an expensive action with a bolt body diameter of greater than 0.700″ which would be desirable on the 0.640″ rim version. However, with the severely rebated 0.590″ rim, reliable feeding is an almost unobtainable goal so the reader is encouraged to avoid this variation. A ballistically identical cartridge called the .585 African Express (Ralston) has been designed by Brad Ralston of South Africa. It uses a full sized rim instead of a rebated rim for use in the Granite Mountain Arms magnum mauser action. The .585 Van Horn also offers similar ballistics with some variations in case dimensions.

Another issue with the .585 Nyati is that many barrels are being produced with excessively tight chamber necks. The author believes this may be due to an error in original drawings for the cartridge. If your barrel maker sends you a barrel with a tight neck, just ream it out to 0.614″ with a neck reamer and tight necks (and dangerous pressures) will not be a problem. Rifles for the .585 Nyati cartridge should weigh a minimum of 11 pounds and preferably 13 pounds in order to make them controllable. For hunting purposes, the owner of a .585 Nyati should consider keeping his velocities below 2300 feet per second or follow up shots will be slow.

The author has used the .585 Nyati on elephant and buffalo with satisfactory results. Both were heart/lung shots at under 25 yards, and in each case the game traveled less than 20 yards before collapsing. The buffalo was spooked before being shot, but his adrenaline was no match for a 750 grain solid moving at 2250 feet per second. The recoil is violent and always surprising. I can shoot 10-14 shots of .585 Nyati in a day, but only if I take Tylenol before going to the shooting range.

At present I know of no factory rifles in .585 Nyati nor are there likely to ever be any. Rifles in this cartridge are strictly a custom affair, and ammunition should only be loaded by the advanced reloader. Although the .585 Nyati is a very effective and fun cartridge, it is not very practical. Brass can be of inconsistent quality and/or in short supply. Only big bore experts are likely to get a rifle in this cartridge to feed properly, and the labor cost of doing so will be significant.

Example loads:

Cartridge Powder Primer Bullet Velocity Notes
585 Nyati 2.8″ 130.0 grains Reloader 15 F215 750 grain TCCI solid 2250 f.p.s. This is the author’s recoil limit.
120.0 grains IMR4350 750 Woodleigh 2050 f.p.s. Approximates 577 Nitro Express factory load.
90.0 grains H4831 1200 grain cast 1300 f.p.s. Low recoil practice load.