The .257 Roberts (.257 Roberts +P)
By Chuck Hawks
Illustration courtesy of Hornady Mfg. Co.
The .257 Roberts may be a better choice for a combination of varmint and big game hunting than the .24's for the reloader with a strong bolt action or single shot rifle. No less an authority than Jack O'Connor, the Dean of American gun writers, thought so. Jack considered the .257 a more flexible cartridge than the .243 Winchester or the 6mm Remington.
The .257 Roberts is based on a necked-down 7mm Mauser case, and was legitimized by Remington in 1934. From then until the introduction of the hot .243 Winchester and .244/6mm Remington in 1955, the .257 was the top selling combination varmint/deer cartridge. A few years after the introduction of the hot .24's, the .257 had almost disappeared from new factory rifles. Ruger saved the cartridge by offering it in its excellent M 77 bolt action rifle in 1972, sparking a return of interest in the .257. Later, in the 1980's, both Remington and Winchester offered it in their fine bolt action rifles, and now the .257 Roberts is back.
The .257 is offered in a number of factory loads with 117-120 grain bullets. The 120 grain spitzer bullet as factory loaded by Federal claims a muzzle velocity (MV) of 2,780 fps and muzzle energy (ME) of 2,060 ft. lbs. At 200 yards the velocity is 2,360 fps and the energy is 1,480 ft. lbs.
Hornady offers a factory load in their Light Magnum line that drives a 117 grain spire point bullet at a MV of 2,940 fps and muzzle energy (ME) of 2,245 ft. lbs. At 200 yards the velocity is 2,460 fps and the energy is 1,572 ft. lbs. The trajectory of that load should look about like this: +2.6" at 100 yards, +2.1" at 200 yards, -3.9" at 300 yards. The maximum point blank range (+/- 3") is 289 yards.
This Hornady load is listed as a "+P" load. The reason for this absurdity is that when the .257 was new, clear back in the 1930's and '40's, it was chambered in some actions of questionable strength. Because of this the factories have kept the .257's maximum allowable pressure well below what is normal for high intensity cartridges chambered in strong bolt action rifles. If you own a modern rifle there is no reason why you cannot load the .257 to the same pressure as any other high intensity cartridge.
In recent years the factories have partially rectified the problem by loading higher pressure cartridges for modern rifles only, and labeling them "+P." The performance of these +P loads (with the exception of the Hornady Light Magnum load cited above) is still below what can be safely achieved by the handloader with a decent bolt action or single shot rifle, but they at least get the .257 up off its knees.
For the handloader, the Speer Reloading Manual Number 13 lists the following loads. An 87 grain spitzer in front of 47.0 grains of H4350 powder for a MV of 3161 fps, or 51.0 grains of the same powder for a MV of 3381 fps. A 100 grain spitzer in front of 41.0 grains of W760 powder for a MV of 2804 fps, or a maximum load of 45.0 grains of W760 for a MV of 3113 fps. The 120 grain spitzer with 41.0 grains of IMR 4831 powder for a MV of 2552 fps, or 45.0 grains of IMR 4831 for a MV of 2793 fps. Winchester cases and CCI primers were used for all of these loads, which were chronographed in a 24" barrel.
The older Speer Reloading Manual Number 10 showed a top load for the 120 grain bullet was 2,866 fps, and it listed three powders capable of driving the 120 grain spitzer over 2,800 fps. I suspect we have the lawyers to thank for the change. In any event, these numbers do bear out the truth that the .257, based on the same case as the 6mm Remington, can drive the same weight bullet to the same or slightly greater velocity at the same pressure. However, with the same weight bullet, the .24 caliber is superior in both BC and SD.
What gives Jack O'Connor's argument credence is the fact that the .257 can handle the heavy 117 and 120 grain bullets. The BC of the Speer 120 grain spitzer is .410 and the SD is .260. These figures are roughly comparable to the numbers for Speer's heaviest 6mm bullet, the 105 grain spitzer (BC .443, SD .254). With the .257 you are making a slightly bigger hole and hitting the animal with a heavier bullet.
At 300 yards the factory ballistics table shows 1,270 ft. lbs. of energy for the 6mm/105, and 1,240 ft. lbs. for the .257/120. My guess is that a deer or antelope struck with either one would not be able to tell the difference.