Compared: The .338x57 O'Connor and .358 Winchester
By Chuck Hawks
Jack O'Connor proposed the wildcat .338x57 in his Jack O'Connor's Gun Book, which was published in 1953. When he first conceived the idea I do not know. Clearly it was sometime after the introduction of the .348 Winchester in 1936 and prior to the advent of the .358 Winchester in 1955. His idea of an ideal deer and black bear cartridge was a .33-.35 caliber that would throw a flat nose bullet (for optimum brush penetration) weighing 200-225 grains at a muzzle velocity (MV) of 2400-2450 fps without producing more recoil than the average deer hunter could withstand (about 20 ft. lbs. according to most experts). He felt that the .348 Winchester was the best woods cartridge of the time, but that it kicked too hard for the average hunter.
The 7x57 case necked up to accept .338" bullets was O'Connor's solution to the problem. I wrote an article titled "Woods and Brush Rifles" in which I favorably described Jack O'Connor's proposed cartridge, and I called it the ".338x57 O'Connor." The cartridge seemed to generate some interest, so I did more research and followed-up with an article ("New Woods Cartridge: the .338x57 O'Connor") describing the .338-57 in considerable detail. In that article I worked out the specifications, ballistics, and anticipated recoil.
The 7x57 case is a rimless design that uses a standard .473" rim diameter. It has a medium powder capacity, about two grains of water greater than the .308 Winchester case and 12-13 grains of water less than the .30-06 case. It is slightly shorter in length than a .30-06 and will work through any standard length rifle action. Suggested maximum average pressure (MAP) for the .338x57 is 52,000 cup and/or 62,000 piezo psi.
The ballistic performance of the .338x57 as envisioned by Jack O'Connor was right on the money. It should be able to easily drive a 200 grain bullet at a MV of 2400 fps with ME of 2558 ft. lbs., and a 225 grain bullet at a MV of 2300 fps with ME of 2640 ft. lbs. In fact, I believe that with maximum loads it could handily exceed these velocities, but the whole point of the .338x57 is moderate velocity for outstanding brush bucking potential and manageable recoil.
Winchester introduced their .358 cartridge in 1955, just two years after O'Connor proposed his .338x57. The .358 was intended to duplicate the ballistics of the classic .348 Winchester in a cartridge that would work in short action (.308 length) rifles. It is based on the .308 Winchester case necked-up to accept .358" bullets. The .358 Winchester is loaded to a MAP of 52,000 cup and/or 62,000 piezo psi.
The sole .358 Winchester factory load drives a 200 grain Silvertip spitzer bullet at a MV of 2490 fps with ME of 2753 ft. lbs. At one time there was the option of a 250 grain Power Point bullet at a MV of 2250 fps with ME of 2810 ft. lbs., but that load has been discontinued. Factory loaded ammunition is available only from Winchester.
Reloaders can drive a 200 grain bullet at approximately 2500 fps or a 220-225 grain bullet at over 2400 fps with ME of 2814 ft. lbs. The Speer 220 grain Flat Point bullet would be a good choice for a woods rifle.
The proposed ballistics of the .338x57 O'Connor are much like those of the later .356 Winchester, including the standard flat point bullet, and in some ways that would be a better comparison. However, because the .356 was designed specifically for the Big Bore Model 94 rifle, it has a rimmed case. The .358 uses a standard rimless case based on the .308 Winchester, and was intended for modern autoloading, lever action, and bolt action rifles, as is the .338x57. So I chose to compare the .338x57 to the .358. Both adaptable to autoloaders such as the Remington 7400 and Browning BAR, the Remington 7600 pump action, modern lever action rifles such as the Browning BLR, and almost all popular bolt action and single shot rifles.
There is a basic difference in concept between the .358 and .338x57. The former was designed for the maximum performance attainable given its case capacity and is loaded to maximum pressure. The .338x57, on the other hand, was conceived to offer excellent performance at woods ranges at a recoil level with which the average shooter could live. Since the .338x57 can be loaded to the same MAP as the .358 Win. the two should be essentially equal with any given bullet weight, if both are loaded to full power. The price, of course, would be increased recoil.
Let's start by comparing the sectional density (SD) and ballistic coefficient (BC) of appropriate .338 and .358 bullets. Sectional density is computed by dividing a bullet's weight (in pounds) by the square of its diameter (in inches). SD matters because it is one of the major factors in bullet penetration, which is important for woods cartridges in general and even more important for medium bore woods cartridges that may be used on large (CXP3 class) game as well as deer and black bear. The higher the sectional density figure the better the penetration, all other factors being equal. Many authorities, including Jack O'Connor, consider bullets of equal sectional density to be a better comparison than bullets of equal weight.
Ballistic coefficient is an expression of a bullet's aerodynamic efficiency. The higher the number, the more of its initial velocity a bullet retains as it travels downrange. BC does not affect SD. Spitzer (pointed) bullets are available in most weights for both calibers, and have a higher BC, but because these are woods cartridges I have chosen flat point or round nose bullets when possible for their improved brush-bucking capability.
The 225 grain .338 bullet has a SD widely recommended for large animals such as elk and moose (CXP3 class game). The 200 grain .338 and 220 grain .358 bullets have SD's generally regarded as good for multi-purpose bullets to be used on mixed bag hunts (mule deer and elk, for example). The 200 grain .358 bullet is most suitable for CXP2 class game, such as deer and black bear. Clearly, for any given weight, a .338" bullet will have better SD than a .358" bullet.
The cross-sectional area (frontal area) of a bullet is also important. The greater the frontal area, the bigger the hole it makes in the target. The frontal area of a .338" bullet is .0897 sq. in.; the frontal area of a .358" bullet is .1007 sq. in. This advantage of the .358 caliber is constant regardless of the bullet's weight.
Next, let's look at velocity. The .358 Winchester can drive a 200 bullet at a muzzle velocity of about 2500 fps and a 220 grain bullet to a MV between 2360 and 2480 fps. So can the .338x57, but it is intended to be loaded to a MV of 2400-2450 fps with a 200 grain bullet, or a MV of approximately 2300 fps with a 225 grain bullet.
Velocity has a big impact on energy, of course, and energy affects killing power. The following are the 100 and 200 yard energies for typical loads in both calibers.
Those energy figures are interesting. While the .358 in our example starts a 220 grain bullet 100 fps faster at the muzzle and with more energy than the .338 starts a 225 grain bullet, the superior ballistic coefficient (BC) of the trimmer .338 bullet allows it to hit harder down range.
Trajectory is not usually of primary importance with medium bore woods cartridges, but not all game is shot right off the muzzle, either. Here are the approximate trajectories of our four selected loads, calculated for a line of sight 1.5" over the bore (as with a low mounted scope).
Another way to examine trajectory is based on Maximum Point Blank Range (+/- 3"). Zeroing a rifle for the MPBR maximizes the trajectory potential of all bullets and loads. As can be seen from the following, all four loads have a MPBR well in excess of 200 yards, and there is little to choose between them.
The hardest factor to quantify is killing power. We know that energy, penetration, and bullet frontal area are all important factors in killing power, but not exactly what is the best blend of these factors. Bullet performance is also of tremendous importance; fortunately, bullets of similar performance are available for both calibers. As always, bullet placement is the biggest single factor in killing power, but that is beyond the scope of this article.
The .338 has the deepest penetration with any given bullet weight, and hence a longer wound channel, while the .358 creates a wider wound channel. The .358 has a modest advantage in energy at all ranges with the 200 grain bullet, because it is loaded to higher velocity, and to slightly past 100 yards with the 220 grain bullet. Beyond that distance the 225 grain bullet for .338x57 delivers the most energy.
An indication of killing power is the "Optimal Game Weight Formula" developed by Edward A. Matunas. I figured the maximum optimal game weight at normal ranges for each load and got the following results at 100 and 200 yards.
It is no surprise that these figures favor the heavier bullets in each caliber. In fact, there is practically nothing to choose between the .338/225 and .358/220. The .358/200 has a modest advantage over the .338/200 in optimal game weight at all ranges due to its higher energy. This could be equalized should we choose to load the .338-57 to full pressure, but that would increase recoil. In any case, with 200 grain bullets both calibers are adequate for even very large North American deer at 200 yards.
The final factor to consider when choosing any hunting rifle is recoil. In the case of these two cartridges, there does not appear to be much difference. The "Rifle Recoil Table" shows the following free recoil figures for 8 pound rifles chambered for the .338x57 O'Connor and .358 Winchester.
Ammunition availability is always an important consideration for any rifle. Neither the .338x57 nor the .358 Win. are particularly good in this regard. The former is a wildcat and all ammunition must be handloaded, period. The latter has one factory load available from one manufacturer. Unfortunately, many sporting goods stores do not stock .358 Winchester ammunition due to slow sales, and the single Winchester factory load, with its 200 grain spitzer bullet, is not the best choice for woods hunting. However, .358 cases are easy to form from .308 brass, just as .338x57 cases are easily formed from 7x57 brass. Most shooters owning a rifle for either caliber are probably going to need to reload their own ammunition, so in this case the availability of a single factory load for the .358 Winchester is only a slight advantage.
There is a somewhat better choice of .338" bullets than of .358" bullets. However, there are enough alternatives in both calibers to satisfy practically any need. The .338x57's advantage in terms of bullet selection is thus more theoretical than real.
A couple of technical factors related to the design of the two cartridge cases should be mentioned. Both the .338x57 and .358 Winchester are adaptable to a wide range of single shot, lever action, pump, autoloading, and bolt action rifles. However, the .358 has a very small shoulder due to its fat bullet, and a strong firing pin blow can set the case forward in the chamber. This was reported to be the reason why Winchester dropped the .358 from the Model 70 bolt action rifle line. The .338x57 O'Connor, with a wider shoulder, has no such problem.
Also, the .338x57 has a longer cartridge overall length (COL). It requires a standard length action, where the .358 is adapted to short action rifles. This greater overall length allows the .338x57 to use heavy 250 grain spitzer bullets, if desired, without sacrificing undue powder capacity. 250 grain bullets in the .358 protrude deeply into the powder space inside the case. The shooter who requires a short action rifle must choose the .358 Winchester, most others will be better served by the greater loading flexibility of the .338x57 O'Connor.
To recap what we have learned, for any given weight .338 bullets will have superior sectional density, and .358 bullets will always have a greater frontal area. Loaded to their maximum average pressure of 62,000 psi the ballistic performance of the two cartridges will be just about identical. Even with the .338x57 loaded to less than maximum velocity, 100 fps slower than the .358 Win. in the examples above, the difference in performance is minimal. In terms of trajectory and killing power there is little to choose between the two cartridges.
Just as neither caliber is dominant in performance terms, there is also no real winner in terms of recoil, although the .338x57 with the 225 grain bullet probably delivers the best bang (killing power) for the recoil buck, so to speak. Since both cartridges should appeal primarily to the reloader, any balance of performance and recoil desired can be selected for either caliber.
The main difference between the two cartridges is probably their fundamental design. The .358 Winchester is designed for short action rifles, which average about 1/2 inch less in overall length than rifles with standard length actions. Providing the prospective owner does not insist on a short action rifle, the .338x57 O'Connor appears to be a fundamentally superior cartridge. The longer COL of the .338x57 makes it a more flexible choice for the reloader, and its wider shoulder makes it more reliable, particularly for use in bolt action rifles. Both are fine calibers, however, and the savvy woods hunter will not go wrong with either.
Copyright 2003, 2014 by Chuck Hawks. All rights reserved.