6.5mm (.264 caliber) cartridges have long been popular in Europe and Africa, but less so in North American. In recent years this has changed and now North American hunters have a variety of 6.5mm cartridges from which to choose.

Interestingly, the rise of the 6.5mm, especially among the long range target shooting crowd, has brought it into conflict with 6mm (.243 caliber) cartridges. This seems strange to me, as there is enough difference in the typical bullet weights to clearly differentiate the two calibers.

However, long range match shooters are achieving similar long range trajectories with the two calibers and 6mm cartridges kick less than 6.5mm cartridges of the same general case capacity, as .243" bullets of a given ballistic coefficient (BC) are lighter than 6.5mm bullets. Lighter recoil always translates to more accurate shooting, especially over the duration of a long match.

A comparison of 6mm and 6.5mm cartridges seems to be in order. For the sportsman and hunter, the most popular 6mm cartridge, by far, is the .243 Winchester. Among the established American 6.5mm cartridges is the .260 Remington, which happens to be based on the same .308 parent case as the .243 Winchester.

The .243 and .260 cases are identical from the rim to the shoulder and both have a 20 degree shoulder angle, making for a very fair comparison of extremely similar (except for bullet diameter) short action cartridges. Both cartridges are loaded to the same SAAMI maximum average pressure of 52,000 CUP or 60,000 psi.

The .243 Winchester

Winchester developed the .243 in 1955 as a combination varmint and deer cartridge for their short action Model 88 lever, Model 100 autoloading and Model 70 bolt action rifles. It became an immediate success and has been a best seller ever since. The .243 is based on the .308 Winchester case necked-down to accept standard .243" (6mm) diameter bullets.

All of the major US ammunition companies offer .243 factory loads. There are many bullet weights available, but typical .243 varmint loads launch an 80 grain bullet at a muzzle velocity (MV) of 3350 fps and typical factory loads for hunting Class 2 game drive a 100 grain bullet at a MV of 2960 fps. Reloaders can safely achieve velocities similar to the factory loads.

Over the years the .243 has proven to be an effective deer and antelope cartridge. Tens of thousands of new and recoil sensitive shooters have learned to hunt medium game with a .243 rifle.

The .243 is offered in a very wide variety of rifles including bolt, lever, pump, autoloading and single shot types. Few, if any, cartridges are available in a greater number of rifles. The most enduring and popular models have always been bolt actions, such as the Browning X-Bolt, Remington Model 700 and Seven, Ruger M77, Savage Model 110 series and Winchester Model 70.

The .260 Remington

The .260 Remington is based on the .308 Winchester case necked-down to accept standard .264" (6.5mm) diameter bullets. Winchester skipped .264 when they introduced their series of cartridges based on the .308 Winchester case in the 1950s. It wasn't until 1997 that Remington standardized the wildcat 6.5mm-08 as the .260 Remington.

Like all 6.5mm cartridges, its biggest advantage is the high sectional density (SD) of its bullets. Remington .260 factory loads drive a 120 grain bullet (SD .246) at a MV of 2890 fps, a 125 grain bullet (SD .256) at a MV of 2875 fps and a 140 grain bullet (SD .287) at a MV of 2750 fps.

These are all intended for hunting Class 2 game, but the "money" load for the .260, and all other serious 6.5mm hunting cartridges, is the 140 grain bullet. This extends the cartridge's capability to include the largest Class 2 animals (adult male black bear and caribou, for example) and the smaller Class 3 animals.

Federal, Hornady and Nosler also offer factory loaded .260 ammunition. Reloaders can safely achieve velocities similar to the factory loads.

Remington, Ruger and Kimber have chambered their bolt action and single shot rifles for the .260 Remington cartridge. Browning, Savage and Winchester have done so to a limited extent in the past.

The Comparison

We will compare our two cartridges in velocity, kinetic energy, trajectory, sectional density, bullet cross-sectional area, killing power and recoil. At the end I will make some concluding comments.

For comparison loads we will use standard Remington factory hunting loads with Core-Lokt Pointed Soft Point bullets, the same ammunition millions of hunters hunt with every year. In .243 that would be the 100 grain Core-Lokt PSP (BC .356) and in .260 it would be the 140 grain Core-Lokt PSP (BC .435).

Velocity

Above some certain impact velocity there may (or may not) be a "shock" effect on an animal's system. That theory is widely debated and difficult to prove. However, for certain higher velocity flattens trajectory. Velocity is also a major factor in computing kinetic energy.

Here are the Remington velocity figures (in feet per second) at the muzzle, 100, 200, 300 and 400 yards for our selected factory loads.

• .243 Win, 100 grain: 2960 MV, 2697 at 100 yards, 2449 at 200 yards, 2215 at 300 yards, 1993 at 400 yards
• .260 Rem, 140 grain: 2750 MV, 2544 at 100 yards, 2347 at 200 yards, 2158 at 300 yards, 1979 at 400 yards

The velocity champion is the .243 Winchester. The .243 starts with a 210 fps advantage, but at 400 yards its advantage has shrunk to only 14 fps. We will see how the difference in velocity affect trajectory shortly.

Energy

Energy delivered on target, bullet diameter and bullet penetration are the keys to killing power. The bullet's remaining energy at impact powers penetration and expansion.

Kinetic energy is essentially a function of mass and the square of velocity. Here are the Remington energy figures for our comparison loads from the muzzle to 400 yards in foot-pounds (ft. lbs.).

• .243 Win, 100 grain: 1945 ME, 1615 at 100 yards, 1332 at 200 yards, 1089 at 300 yards, 882 at 400 yards
• .260 Rem, 140 grain: 2351 ME, 2011 at 100 yards, 1712 at 200 yards, 1448 at 300 yards, 1217 at 400 yards

In this important category the relatively heavy bullet of the .260 Remington pays dividends the higher velocity of the .243 cannot overcome.

Trajectory

Trajectory is important because a bullet that shoots flatter is easier to place accurately as the range increases and bullet placement is, by far, the most important factor in killing power. The following trajectory figures are predicated on scoped rifles with the line of sight 1.5" above the center of the bore.

For comparison purposes, each load is zeroed at 200 yards. Trajectory figures are given in inches above or below the line of sight from the muzzle to 400 yards.

• .243 Win, 100 grain C-L PSP: -1.5" at muzzle, +1.6" at 100 yards, 0 at 200 yards, -7.5" at 300 yards, -22.1" at 400 yards
• .260 Rem, 140 grain C-L PSP: -1.5" at muzzle, +1.9" at 100 yards, 0 at 200 yards, -8.3" at 300 yards, -24.0" at 400 yard

The .243 Winchester, due primarily to its higher velocity, has the flattest trajectory across the board. The difference, however, is not great, amounting to less than an inch at 300 yards.

Sectional Density

The sectional density (SD) of bullets is calculated by dividing a bullet's weight (in pounds) by the square of its diameter (in inches). Note that the shape, material or ballistic coefficient of the bullet has no bearing on SD, only weight and diameter count.

Sectional density is important because, all other factors being equal (especially bullet expansion characteristics), the bullet with the highest SD will penetrate the deepest. A simple example is that a long and slender shape, like a needle, penetrates better than a blunt shape, such as a round ball, of the same weight at the same velocity.

The deeper the wound channel (of any given diameter) in a game animal the more tissue is destroyed and the greater the killing power. The .243 Winchester shoots .243" diameter bullets and the .260 Remington shoots .264" diameter bullets. Here are the SD numbers for our selected bullet weights.

• .243 Win, 100 grain = .242
• .260 Rem, 140 grain = .287

SD's above about .205 are considered adequate for hunting Class 2 class game animals (deer, antelope, goats and sheep, for example) with small bore rifles, meaning .24 to .32 caliber. Properly designed bullets with SD's above about .250 are regarded as suitable for hunting Class 3 game, assuming other factors (energy and cross-sectional area, for example) are also adequate.

The SD of the .243/100 grain Core-Lokt bullet is more than adequate, in terms of penetration, for hunting Class 2 animals. The SD of a 100 grain .243 bullet is identical to the SD of the famous 130 grain .270 bullet and the velocities are also similar, which helps explain the .243's proven effectiveness on Class 2 animals.

The SD of the .260/140 grain Core-Lokt bullet is excellent not only for Class 2 game, but also for Class 3 animals. This is why 6.5mm cartridges have earned such an outstanding reputation in game fields around the world for deep penetration.

Cross-sectional Area

Bullet cross-sectional area is important, because the wider the wound cavity (of any given depth), the more tissue is destroyed and the greater the killing power. Bullet cross-sectional area is independent of bullet weight. The actual bullet diameters of our two calibers are .243" and .264". Here are the bullet cross-sectional areas for our calibers.

• .243" = .0464 square inches
• .264" = .0547 square inches

It was a forgone conclusion that the .260 Rem. would win the bullet cross-sectional area comparison. A .264 bullet will, given the same percentage of bullet expansion, always punch a larger diameter hole than the .243 bullet.

Killing Power

Optimum Game Weight (OGW) is a system devised by Edward A. Matunas to express the killing power of rifle cartridges in terms of distance and the weight of the animal. We need not go into the formula itself here, suffice to say that while not perfect, the OGW system does seem to have a higher correlation with reality than most other systems for estimating killing power. The figures below represent animal weight in pounds and distance in yards.

• .243 Win, 100 grain: 389 lbs. at Muzzle, 294 lbs. at 100 yards, 220 lbs. at 200 yards, 163 lbs. at 300 yards
• .260 Rem, 140 grain: 611 lbs. at Muzzle, 485 lbs. at 100 yards, 382 lbs. at 200 yards, 299 lbs. at 300 yards

The .260 Remington has the advantage in theoretical killing power at all ranges. It scores in the Class 3 animal weight range at 100 yards and large Class 2 animal weight range at 300 yards.

In fact, at 300 yards the OGW killing power of the .260 is about equal to the OGW killing power of the .243 at 100 yards. This is not surprising, given the .260's advantage in energy, sectional density and bullet cross-sectional area.

However, note that in OGW the .243 is adequate for adult buck mule deer (average weight 200 pounds) at 200 yards and average size adult whitetail bucks (125 pounds) at 300 yards. Keep in mind that precise bullet placement, not raw power, is what results in quick, clean kills and both of these cartridges, especially the .243, are relatively easy to shoot accurately.

Recoil

Recoil or "kick" is more important than many shooters realize. Everyone shoots better with a gun that kicks less. That has been proven repeatedly. (Just ask the long range match shooters.)

Bullet placement is, by far, the most important factor in achieving a quick, humane kill. Get almost any reasonably appropriate bullet into the vitals and you are in business.

A solid hit in the heart/lung area of a caribou with a 100 grain .243 or 140 grain .260 bullet is far preferable to putting a 270 grain .375 Magnum bullet too far back. Power will not make up for incorrect bullet placement and flinching due to anticipating the rifle's recoil and muzzle blast is the single biggest cause of bad bullet placement.

Here are the approximate recoil energy (in foot-pounds) and velocity (in feet-per-second) figures for our representative loads fired in an eight pound rifle.

• .243 Win, 100 grain at 2960 fps: 9.1 ft. lbs. / 8.6 fps
• .260 Rem, 140 grain at 2750 fps: 12.7 ft. lbs. / 10.1 fps

There is a significant difference in recoil between these two calibers. The flat shooting .243 can be enjoyed by almost all shooters and its low recoil allows hunters to take advantage of the very high level of accuracy delivered by most .243 rifles. The result is precise bullet placement. This is the foundation of the .243's reputation as a good deer and pronghorn slayer.

The .260 kicks noticeably more than the .243, but overall it is still a light kicking cartridge. It is well within the maximum of 15 ft. lbs. of recoil energy with which most reasonably experienced shooters can do good work.

Summary and Conclusion

Our typical .243 Winchester 100 grain Core-Lokt factory load has the advantages of higher velocity, flatter trajectory and lower recoil than our .260 Remington 140 grain Core-Lokt factory load. These are the factors that make it easier to put a bullet where it needs to go. Never forget that accurate bullet placement is the most important factor in achieving clean kills.

This makes the .243 Winchester ideal for the youthful, novice, or recoil sensitive hunter. No wonder it is such a popular caliber for first deer rifles.

On the other hand, the .260 Remington is the more powerful and versatile hunting cartridge. It won the comparison in energy, sectional density, cross-sectional area and OGW killing power, all by respectable margins. It is clearly the more capable hunting cartridge.

The .260's recoil energy is 3.6 ft. lbs. greater than the .243 in an eight pound rifle, which is a very noticeable difference for most beginners, or someone with a bad shoulder. However, it is still 2.3 ft. lbs. under the 15 ft. lb. maximum that most hunters, once they accumulate a reasonable amount of experience, can handle without developing a serious flinch. Many very experienced riflemen are finding the .260 Remington (and its ballistic twins the 6.5x55mm SE and 6.5mm Creedmoor) to be an ideal, general purpose Class 2 game cartridge.