The .376 Steyr (9.55x60)
By Chuck Hawks
Hornady and Steyr introduced the .376 Steyr in 2000 as a joint development. Steyr initially chambered the .376 in a big bore version of their Scout Rifle with a 19" barrel. (Shades of Remington's .350 Mag./Model 600M combination of 1964!) This rifle was soon discontinued, but the 2002 Shooter's Bible lists the Steyr-Mannlicher ProHunter and ProHunter Compact rifles as being chambered for the cartridge. If the .376 has been picked-up by any other manufacturer, it has not come to my attention.
According to Cartridges of the World by Frank C. Barnes, Jeff Cooper had something to do with inspiring the .376 Steyr as a cartridge for the Steyr big bore scout rifle concept. The ideal was a cartridge suitable for dangerous game as large as Cape buffalo that could be chambered in a compact bolt action rifle. The .376 Steyr should fulfill that requirement as well or better than the .350 Remington Magnum, which is the cartridge I remember Mr. Cooper first writing about many years ago in the context of a general purpose or "scout" type medium bore rifle. The .375 caliber bullet was chosen over a .358 caliber bullet for the new cartridge because some African countries require at least a .375 caliber rifle for hunting dangerous game. And, of course, Hornady and Steyr did not know that Remington was planning on re-introducing the .350 Mag. in the new Model 673 Guide Rifle.
Unlike the short action .350 Remington Magnum cartridge, however, the .376 Steyr requires a full length action to accommodate its 3.075" cartridge overall length (COL). The new .376 Steyr case is a bottleneck design 2.35" long with a short, sloping shoulder of approximately 17 degrees and a slightly rebated rim of .494" diameter. The case diameter is .501" at the head and .474" at the base of the shoulder. It accepts standard .375" bullets. The maximum pressure for the .376 is reported to be 62,000 psi and, according to Steyr, factory ammunition is loaded to about 58,000 psi.
The .376 Steyr is based on a shortened version of the 9.3x64 Brenneke case. Taken as a whole this is an unusual case for a modern design. Its rim is smaller than the usual .532" magnum diameter, but larger than the .473" diameter of standard (.30-06 size) cases. Its COL is longer than the 2.8" maximum required for short bolt actions, but not as long as the 3.2" permitted by standard length actions. Ideally a special action should be built for this cartridge length, as Mauser once did for the 7x57 cartridge in their commercial Model 98 action. However, few manufacturers are willing to go to that much extra expense to accommodate a single cartridge. The usual solution is simply to put intermediate length cartridges in standard length actions.
Hornady factory loads come with 225 grain (BC .320, SD .229) and 270 grain (BC .380, SD .274) Spire Point Interlock bullets. The 270 grain bullet is loaded to a nominal muzzle velocity (MV) in a 24" test barrel of 2610 fps with muzzle energy (ME) of 3990 ft. lbs. The 225 grain bullet is a reduced power (and recoil) load and also features an advertised MV of 2610 fps with ME of 3325 ft. lbs. The 270 grain factory load is reported to be delivering a chronographed velocity of about 2560 fps in the 20" barrel of the Steyr ProHunter rifle. Hornady trajectory figures for the 270 grain factory load are as follows: +1.6" at 100 yards, 0 at 200 yards, and -9.75" at 300 yards. The recoil energy of this load in an 8 pound rifle should run about 39 ft. lbs., so the .376 Steyr could not be called easy on the shoulder.
According to Hodgdon reloading data, handloaders can equal the performance of the Hornady factory load giving a 270 grain bullet a MV of 2610 fps using 65.5 grains of VARGET powder, and achieve maximum velocities of about 2910 fps with the 225 grain bullet in front of 68.5 grains of H335, and 2388 fps with 300 grain bullets in front of 59.5 grains of H4895. All loads were developed in Hornady cases using Federal 215M primers, and all loads developed pressures right around 60,000 cup. For African conditions, where excessive heat can cause considerable increases in chamber pressure, it might be wise to reduce those loads.
The Sixth Edition of the Hornady Handbook of Cartridge Reloading shows that 59.4 grains of H4895 will give their 225 grain Spire Point bullet a MV of 2600 fps. 56.3 grains of the same powder will drive their Spire Point or RN 270 grain bullets at a MV of 2400 fps. These would be more reasonable hunting loads in much of sub-Saharan Africa. These loads Hornady cases and Winchester WLR primers and were developed in a 25.5" test barrel.
Early reports are that the .376 Steyr is getting some use in Africa and gaining a good reputation there. I have not read about its use in North America yet, although it is obviously adequate for all North American game with the 270 grain bullet.
Copyright 2002, 2012 by Chuck Hawks. All rights reserved.