Compared: The .243 Winchester and .257 Roberts
By Chuck Hawks
The .243 Winchester has been the most popular of the combination varmint/deer cartridges since its introduction in 1955. Today it is the sixth best selling centerfire rifle cartridges in the U.S., and the fifth best selling deer and antelope cartridge. There may be more new rifles chambered for .243 Winchester than for any other caliber. By any measure the .243 has been a tremendous success.
When Remington introduced the .257 Roberts in 1934 it held similar promise. The .257 is based on the medium size 7x57 case, which gives it a modest advantage in powder capacity compared to the family of cartridges based on the later .308 Winchester case. Jack O'Connor once predicted (during WW II) that after the end of the Second World War the .257 would become a top selling cartridge. (I believe he guessed third place for the .257 among cartridges intended for bolt action rifles.) He was wrong in that prediction, although the .257 Roberts was a popular cartridge prior to 1955. It was the introduction of the .243 Winchester that eclipsed the .257 Roberts.
I feel that the primary reason (there were others) that the .257 ultimately failed to meet expectations was that the .257 Roberts was under loaded by Remington. For reasons I fail to understand, the maximum average pressure (MAP) of the .257 Roberts was pegged by SAAMI at 45,000 cup. That is very low for a cartridge of that era intended for use in strong bolt action rifles. Remington essentially castrated the performance of its new cartridge before it was even introduced.
Winchester made no such mistake when they introduced the .243. It was loaded to a MAP of 52,000 cup. This allowed the .243 to achieve maximum performance from its necked-down .308 Winchester case. The .243 quickly became a runaway success while the earlier .257 languished. From that time on the majority of shooters bought .243 rifles instead of .257 rifles.
In the 1980s Winchester introduced a "+P" .257 Roberts factory load. This was loaded to a MAP of 50,000 cup, which is more like it. Handloaders, of course, had been turning out such loads unofficially since the .257 Roberts was first introduced. New life was breathed into the .257, and it has made a modest comeback, although it has never approached the popularity of the .243 Winchester. You can read more about the .243 Winchester and the .257 Roberts on the Rifle Cartridge Page, where there are complete articles devoted to each.
In any case, it is well past time to revisit the .243 vs. .257 issue. And we will use both factory loads and maximum handloads to do so. We will compare sectional density (SD) and ballistic coefficient (BC), velocity, energy, trajectory, bullet cross-sectional area, killing power and recoil. We will finish by touching on the availability of both rifles and ammunition.
While both the .243 Winchester and .257 Roberts are combination varmint/deer cartridges, the great majority of shooters today purchase hunting rifles rather than varmint rifles in either caliber. Both calibers are fine, long range, low recoil cartridges for hunting deer and antelope (CXP2 class game). And that is how they will be compared here.
We will compare three different bullet weights for each caliber, including a high performance factory load for each. Game bullets available to reloaders typically range from 90-105 grains in .243, and from 100-120 grains in .257. The heaviest bullet commonly factory loaded in .243 Winchester weighs 100 grains, while in .257 Roberts factory loads are available with bullets weighing up to 120 grains.
Remington has a long and checkered history of not supporting their own cartridges with rifles and state of the art ammunition. This is certainly true in the case of the .257 Roberts. As I write this article no Remington rifles are chambered in the caliber and the only factory load Remington offers is the standard (low) pressure 117 grain bullet at a MV of 2650 fps. Hornady, Winchester and Federal load (+P) 117-120 grain bullets at a MV of 2780 fps, which is more like it. Hornady also goes one better with a "Light Magnum" load that drives a ballistically excellent SST bullet at a MV of 2940 fps. THAT is the factory load that .257 fans have been waiting for all these years! We will use the Hornady Light Magnum factory load to represent the .257 Roberts in this comparison.
Standard factory loads in .243 Winchester, available from most manufacturers, drive a 100 grain bullet at a MV of 2960 fps. Hornady (Light Magnum) and Winchester (Supreme) offer premium .243 factory loads that launch a 95 grain bullet at a MV of 3100 fps. The Hornady Light Magnum load uses a 95 grain SST bullet, so for the sake of consistency that is the factory load that will represent the .243 Winchester.
Nosler offers a .257/100 grain version of their popular Ballistic Tip boat-tail spitzer bullet to reloaders. That bullet has a SD of .216 and a BC of .393. According to the fifth edition of the Nosler Reloading Guide a near maximum load of IMR 4895 powder can drive that bullet to a MV of 3100 fps, so that will be our .257 Roberts reload representing a light game bullet in .257 Roberts.
For a lighter game bullet in .243 we will use the Nosler 90 grain Ballistic Tip, which can be driven to a MV of 3300 fps by a maximum load of AA3100 powder. That will be our light bullet reload in .243 Winchester.
120 grains is the usual choice for a heavy bullet in .257 Roberts. There are numerous alternatives available to reloaders, among which the 120 grain Speer Hot-Cor spitzer is representative. Such bullets can be driven to a MV of around 2800 fps without exceeding a MAP of 50,000 cup.
The heaviest bullet commonly available in .243 caliber weighs 105 grains. Speer also offers a Hot-Cor spitzer in that weight. Maximum loads for that bullet weight in .243 Winchester are usually around 2900 fps MV, so that is the velocity that we will use.
Sectional Density and Ballistic Coefficient
Sectional density, not bullet weight, is probably the fairest way to compare different caliber cartridges. In this comparison, for example, the 90 grain .243 and 100 grain .257 are the most closely comparable loads.
Sectional density is important because the greater the SD, the longer a bullet is for its weight and, other factors being equal, a long skinny bullet of any given weight penetrates better than a shorter, fatter bullet of the same weight. Penetration is an important factor in the length of the wound channel, and the amount of tissue disrupted.
Ballistic coefficient is a measurement of how well a bullet flies through the air. The higher the BC, the lower the bullet's air drag. A higher BC helps a bullet retain more of its initial velocity and energy down range and also results in a flatter trajectory. Here are the sectional densities and published ballistic coefficients for the bullets used in the loads compared in this article.
As you can see, the lighter pair of bullets have very similar sectional densities. In high performance factory loads the .257 has a clear advantage in SD. In fact, the 117 grain .257 bullet is virtually equal to the 105 grain .243 bullet in SD. The advantage here goes to the .257 for its ability to handle heavier bullets of greater SD as required.
Velocity is the most important component of energy and also decreases bullet flight time and hence flattens trajectory. Some hunters feel that high velocity per se contributes to killing power, but that has proven difficult to prove scientifically. Here are the velocities from the muzzle (MV) to 300 yards in feet per second for our selected loads.
The .243 bullets, being lighter, generally start faster and, because they are of similar BC, they retain a velocity advantage down range.
Kinetic energy is a way to measure a bullet's ability to do work. The "work" in this case is expanding and penetrating deep into a game animal to destroy the maximum amount of tissue and kill quickly.
Energy is an important factor in cartridge performance and killing power. Kinetic energy is a good indicator of the power of similar rifle cartridges, such at the .243 Winchester and .257 Roberts. Here are the energy figures in foot pounds for our selected loads from the muzzle (ME) to 300 yards.
The .257 Roberts has the down range energy advantage with all loads. This is most pronounced with our Hornady Light Magnum factory loads due to the greater disparity in bullet weight.
Both the .243 and .257 are relatively flat shooting cartridges. The flatter a bullet shoots the less the shooter needs to compensate for bullet drop and the better his or her shot placement is liable to be. The following trajectories (in inches) are computed for a 200 yard zero and assume an optical sight mounted 1.5" over bore.
As shown by these figures, the .243 has a slight trajectory advantage with all loads. This is primarily due to the higher velocity of its lighter bullets. However, between 0 and 200 yards the difference is inconsequential, and it amounts to less than 3/4 inch even at 300 yards. That is not much!
Bullet Cross-Sectional Area
The cross-sectional area of a hunting bullet is important because, other factors being equal, the fatter bullet makes a wider wound channel and damages more tissue. This translates to quicker and more humane kills. Bullet weight has no bearing on frontal area, only caliber. The actual bullet diameter of .243 Winchester bullets is .243"; the diameter of .257 Roberts bullets is .257". Here are the frontal areas of each:
The .257 has a clear advantage in bullet frontal area and consequently the potential for a wider wound channel.
This very important category is, as they say, where the rubber meets the road. Unfortunately, it is the hardest to quantify due to the large number of variables involved. Bullet placement is the most important factor in a cartridge's effectiveness on game, and that is largely a function of the shooter's skill and judgment, not the cartridge itself. The construction and performance of the bullet is also very important, which is one of the reasons why we have chosen to compare pairs of bullets of the same basic design.
An attempt to include at least some of the factors relevant to killing power (primarily impact velocity and bullet weight) is the Optimum Game Weight (OGW) formula developed by Edward A. Matunas and published in the Lyman 47th Reloading Manual. Matunas assumed that bullet design and placement are adequate for the task at hand. The numbers below indicate the size of animal (by weight) for which each load is presumably optimum at 200 yards. (For more on OGW, see the "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists Page.)
Here are the OGW figures at a distance of 200 yards for each of our .243 Winchester and .257 Roberts loads.
With every load in our comparison the .257 Roberts has the advantage in killing power. The difference is not extreme, but it is there. As Jack O'Connor--the Dean of American gun writers--wrote years ago, the .257 should kill medium size game animals better than the .243 because of its heavier, larger diameter bullets.
The .243 and .257 are both known for their relatively light recoil. Here are the recoil energy (in foot pounds) and velocity (in feet per second) numbers for the heavy bullet loads in each caliber, computed for 8 pound rifles.
The .243 wins this comparison by 1.7 ft. lb. and 0.8 fps (roughly 15% and 9% respectively). That is enough difference to be noticeable at this recoil level. It might be meaningful to someone who is recoil sensitive, but is probably not of much consequence to the majority of shooters.
Availability of Rifles and Ammunition
Here there really is no comparison. The .243 Winchester is available in a very wide variety of rifles brands and types, while the availability of rifles is .257 Roberts is restricted to only a few individual models.
The same situation pertains as regards factory loaded ammunition. The 2007 Shooter's Bible lists almost an entire page of .243 Winchester factory loads from just about every company that sells factory loaded ammo in the U.S. The same source lists a total of only five factory loads for the .257 Roberts. These are from Federal, Hornady, Remington, and Winchester. The Shooter's Bible listing is not all-inclusive, but it is representative of the comparative difference in available factory loads.
Both the .243 Winchester and .257 Roberts are well regarded medium game calibers here at Guns and Shooting Online and by experienced hunters generally. I, for example, own and use fine rifles in both calibers.
Depending on what they regard as the most important factors, some shooters favor the .243 while others favor the .257. Now, at least, you have the facts to make your own informed judgment.
Copyright 2006, 2012 by Chuck Hawks. All rights reserved.