The .243 Winchester: Its Capabilities as a Deer Cartridge
By Gary Zinn
The .243 Winchester cartridge, introduced in 1955, is very popular. Currently, it ranks sixth among the best selling cartridges in the USA, just behind the .270 Winchester and ahead of the 7mm Remington Magnum. The reasons for the enduring popularity of the .243 are well summarized by Chuck Hawks in his article The .243 Winchester:
"The .243 Win. will cycle through almost any short action rifle, whether bolt, lever, pump, or semi-auto. The .243 has become a favorite of hunters who want to shoot varmints, predators and deer size game with the same rifle. It has also become almost the standard long range deer and antelope cartridge for beginning hunters. Recoil energy is low, about 10 ft. lbs. for most loads, and trajectory is flat, both of which contribute to the .243's reputation for deadly practical accuracy."
However, the .243 Winchester has limitations when used to hunt deer and other Class 2 game. The main limitation being the .243 bore size restricts the maximum weight of hunting bullets to about 105 grains. The .243 Winchester cartridge somewhat compensates for the bullet weight limitation by driving its bullets at high velocity.
For instance, the most common 100 grain factory loads claim a muzzle velocity of 2960 f.p.s. from 24 inch barrels, while the hottest handloads listed in major reloading guides run between 3000 and 3150 f.p.s. for 100 grain bullets.
Speedy as it is, however, the .243 Winchester cannot drive small diameter, light weight bullets hard enough to keep pace with the terminal performance of larger bore short action cartridges, such as the .260 Remington, 7mm-08 Remington, or the .257 Roberts +P. Ultimately, this means that the Effective Killing Range (EKR) of the .243 Winchester on deer sized game is less than its maximum point blank range (MPBR). I realize this is a bold statement, so I will analyze several commercial loads to support it.
Standard commercial load with 100 grain bullet
Loads generating 2960 f.p.s. of muzzle velocity (24 inch barrel) with 100 grain bullets are offered in many brands of cartridges, making this a de facto "standard" .243 hunting load. I chose the Federal Vital-Shok load with 100 grain JSP bullet to develop the ballistics analysis of these common .243 loads, which are all essentially the same.
In the data summary below, the first line specifies the brand of cartridge, bullet weight and type, muzzle velocity (f.p.s) from a 22-inch barrel, muzzle energy (ft. lbs.) and ballistic coefficient (BC) of the bullet. (I adjusted the MV for a 22 inch barrel, because this is the most common barrel length for .243 rifles.)
The remaining lines of the data summary are key outputs of the ballistics analysis. First, I used the point blank range calculator at www.shooterscalculator.com to calculate a +/- 3 inch MPBR for the load. The resulting MPBR (280 yards in this case) gives me an unambiguous measure of the practical range of the load. I also noted the zero distance of the load.
Using the ShootersCalculator trajectory calculator, I then developed a trajectory table for the load, specifying a maximum range of 280 yards. From the trajectory table, I recorded muzzle energy and the remaining energy at 100 yards and other relevant distances, including the MPBR of the load. The downrange data is needed to do hunting capability index calculations. (The explanation of the indices is abbreviated here, but is more fully discussed in the Appendix, below.)
The first index is the Hornady H.I.T.S. score. Using bullet weight, diameter and 100 yard impact velocity as inputs, the online HITS calculator produces a numerical score for a given load, "643" in this case. In the HITS system, a score of 500 - 900 means the load is suitable for Class 2 game (50 - 300 pounds) at 100 yards. Thus, this load has the power to be effective on deer and other Class 2 game, according to the HITS score.
The second index is the Guns and Shooting Online Rifle Cartridge Killing Power Formula, which calculates the killing power of hunting loads using downrange impact energy, bullet sectional density and frontal area as the input variables. I call the output variable of this formula KPS (for Killing Power Score). For a given load, the formula is:
KPS at y yards = (Impact Energy at y yards) x (sectional density x frontal area), or simply:
The 100 yard KPS of this load is 1571 x .0112 = 17.6. A KPS can be calculated for any range, a capability that is important in ways that I will demonstrate.
.243 Win: Federal 100 gr. JSP, MV 2920 f.p.s. (22 inch bbl.) / ME 1894 ft. lbs., BC .355
In The .30-30 Winchester: Its Capabilities as a Deer Cartridge, I used the KPS index to determine the ranges to which various .30-30 loads could be considered to have effective killing power on deer and similar size game. Based on experience and ballistic data analysis, I judge this to be roughly 175 yards for the traditional .30-30 cartridge loaded with a 150 grain flat-point bullet. The 175 yard KPS of this load calculates as 15.0, and I dubbed the 175 yard point the "Effective Killing Range" (EKR) for the load.
Once I had established the KPS - EKR relationship for one load, I realized that I could use the KPS value of 15 as a baseline for determining the EKR of other .30-30 loads, which I did. (Chuck Hawks, originator of the G&S Online Rifle Cartridge Killing Power Formula, used the somewhat more liberal score of 12.5 as the practical minimum for hunting Class 2 game. -Editor) I felt that I could also use that KPS value to determine EKRs of other cartridges and loads, provided that the quarry is deer or similar sized game. Therefore, I am using a baseline KPS of 15 to determine the Effective Killing Range distances of the .243 Winchester deer hunting loads covered here.
The key result of this analysis is that the effective killing range of the .243 load above is 180 yards. This falls well short of both the +/- 3 inch MPBR (280 yards) and zero distance (240 yards) of the load. In other words, its effectiveness is limited by its remaining killing power, not its MPBR. This load does not have the long range, dependable killing power on deer and similar game that its flat trajectory and MPBR might suggest.
Other .243 hunting loads
I evaluated a few other loads. The most powerful load I found is made by Doubletap and features a 100 grain Swift Scirocco II bullet at a MV of 3120 f.p.s. This hot load achieves an EKR of 275 yards, only 25 yards short of its 300 yard MPBR.
.243 Win: Doubletap 100 gr. Swft Scirocco II, MV 3120 f.p.s. (22 inch bbl.) / ME 2162 ft. lbs., BC .384
Loads with lighter bullets did not fare so well. A Hornady load with 95 grain SST bullet gets an EKR of 205 yards, almost a hundred yards short of its MPBR.
.243 Win: Hornady 95 gr. SST, MV 3125 f.p.s. (22 inch bbl.) / ME 2060 ft. lbs. BC .355
Dropping to even lighter bullets, the Nosler 90 grain E-Tip load gets an EKR of only 175 yards, far short of its 300 yard MPBR.
.243 Win: Nosler 90 gr. E-Tip BT, MV 3140 f.p.s. (22 inch bbl.) / ME 1971 ft. lbs., BC .403
Finally, I evaluated some 80 to 87 grain bullet loads and found that they either did not generate a minimum HITS score of 500 at 100 yards, or got EKRs of less than 150 yards. These results indicate that bullets weighing less than 90 grains are not very useful for hunting deer with the .243 Winchester. (.243 bullets weighing less than 90 grains are usually intended for varmint hunting. -Editor)
I believe the bottom line of this analysis is clear. Anyone who uses the .243 Winchester to hunt deer or similar game should use full power loads with 90 grain bullets at minimum; 95 to 100 grain bullets are better.
Forget about loads with bullets lighter than 90 grains, for they do not generate useful downrange killing power, no matter how fast they may exit the muzzle. In addition, realize that the effective killing ranges of even the strongest .243 Win. loads fall short of their MPBR values.
Appendix: HITS, KPS and EKR explained
The Hornady H.I.T.S. classification system uses an online calculator to produce a numerical HITS score for rifle cartridge loads. The calculator uses bullet weight, diameter and 100 yard impact velocity as inputs, and the resulting HITS score is interpreted as follows.
Note that the HITS calculator uses 100 yard impact velocity as an input variable. Thus, HITS scores are keyed to that distance. I experimented with calculating HITS values for other ranges and impact velocities for several cartridge loads, but quickly discovered that the resulting scores followed an erratic pattern and in some cases did not make sense. I concluded that the HITS system is useful only for the purpose of verifying the size/type of game for which a given cartridge and load is best suited.
Killing Power Score (KPS)
The Guns and Shooting Online Rifle Cartridge Killing Power Formula uses downrange impact energy, bullet sectional density and bullet cross sectional area as input variables. Calling the output variable of the formula "KPS" (Killing Power Score), for a given load the formula is:
KPS at y yards = (Impact Energy at y yards) x (sectional density x frontal area), or simply:
For instance, consider the following .30-30 Winchester factory load: Hornady 150 gr. Interlock RN, MV 2350 f.p.s. (20 inch bbl.), SD .226, A = .0745 sq. in.
This load produces 1232 ft. lbs. of energy at 100 yards. Thus, the 100 yard KPS of this load is:
This is merely an example, as KPS can be calculated for any range. This capability is important in ways I will demonstrate.
The KPS formula makes a lot of sense to me. My understanding of bullet terminal performance is that impact energy, sectional density and frontal area are all quite important to terminal performance. The KPS formula combines these variables in a direct, easy to calculate way.
Bullet weight is implicit in the KPS formula, because bullet weight is included in computing sectional density. (SD is the ratio of a bullet's weight in pounds to the square of its diameter in inches.)
Bullet velocity is not neglected, because velocity is the most important factor in calculating kinetic energy. Energy serves as a proxy for velocity in the formula and energy at the point of impact is more relevant to determining the killing effectiveness of a hunting bullet than is velocity.
Whenever any of these variables change, the KPS number changes proportionally. For instance, between 100 and 175 yards, the energy of the 150 grain .30-30 bullet decreases by 27.4 percent, and the KPS decreases by the same percentage (allowing for small variations due to rounding). Therefore, KPS numbers generated from different data inputs (E, SD, or A) are directly comparable. This comparability can be applied not only to different loads for a particular cartridge, but also can be extended to comparisons of different cartridges.
Effective Killing Range (EKR)
Simply put, the Effective Killing Range (EKR) of a given cartridge/load is the distance at which the bullet has enough killing power (i.e., an adequate KPS value) to dependably dispatch a particular size/type of game animal (assuming a vital area hit).
Using deer and similar size game as an example, some popular cartridges, such as the .270 Winchester and .308 Winchester, are so powerful that there is no question that they will dependably fell Class 2 game out to their MPBR range or beyond. However, for milder cartridges, such as the .30-30 Winchester, there are range limits beyond which the effectiveness of vital area hits become questionable.
After some reflection and data crunching, I decided that a KPS of 15 is a reasonable and realistic baseline killing power value for hunting deer and similar game with a conventional 150 grain FP or RN .30-30 load. This translates to an effective killing range of 175 to 180 yards.
I realize that setting a KPS of 15 as a baseline power standard for the .30-30 load is a judgment call, but I am comfortable with it. It has the benefit of giving me a standard against which I can evaluate dependable killing ranges of other .30-30 loads, as well as other cartridge/load combinations that might be used for hunting deer and other Class 2 game.
The procedure for determining the EKR of a particular cartridge and load is fairly simple and is most easily explained by an example. My example is a Federal Premium .243 Winchester load with a 100 grain soft point spitzer bullet. This is a standard 100 grain .243 Winchester factory load at a MV of 2960 f.p.s. from a 24 inch barrel. (I adjusted this to a more normal 22 inch barrel length for a .243 hunting rifle.)
.243 Win: Federal 100 gr. JSP, MV 2920 f.p.s. (22 inch bbl.), BC .355; (SD x A) = (.242 x .0464) = .0112
I started with the baseline KPS for the .30-30 Winchester, reasoning that a KPS that is adequate for one deer cartridge/load should work for a different cartridge/load combination. Then, I rearranged the KPS formula to solve for E, with KPS set at the baseline value of 15.0 and (SD x A) = .0112 for the 100 grain .243 bullet.
E = KPS / (SD x A) = 15.0 / .0112 = 1339 (ft. lbs.)
The result means that the KPS of the load in question will be equal to 15.0 at the range where the energy of the bullet falls to 1339 ft. lbs. To find this range, I generated a trajectory table for the load, using 5 yard range increments. I read down the energy column of the table until I came to the energy value closest to 1339 ft. lbs. This was 1346 ft. lbs. at a range of 180 yards. Thus, 180 yards is the Effective Killing Range of this load.
Anyone who disagrees with the baseline KPS I used here may change the analysis to use any cartridge, load and ballistic parameters they feel accurately reflect effective killing power and range, for deer or other game. The point is that KPS and Effective Killing Range can be very useful tools for shooters who want to evaluate the killing performance of different cartridges and loads.
See The G&S Online Rifle Cartridge Killing Power Formula: Implications and Applications and Determining the Effective Killing Range of Rifle Cartridges for fuller discussion of the killing power formula and effective killing range concepts.
Copyright 2017 by Gary Zinn and/or chuckhawks.com. All rights reserved.