Compared: The 6.5mm Rem. Mag. and .270 Win.
By Chuck Hawks
Neither the 6.5mm Remington Magnum nor the .270 Winchester are new cartridges, although the 6.5 is several decades younger than the .270. Their purpose and capabilities are very similar, but their commercial history could not be more different. The .270 is one of the great shooting success stories, one of the most popular hunting cartridges ever developed. The .270 will likely remain popular for as long as metallic centerfire cartridges are made and used.
The 6.5mm Mag. has a much different history. It was introduced to an indifferent shooting public during the 1960's, never caught on, and was discontinued in the 1990's. In 2004, after the concept of the short magnum had finally taken hold and at the urging of some of the gun writers in the press and online, Remington decided to give their orphan 6.5mm short magnum cartridge a second chance.
Shooters have asked for .270 Winchester performance in a short action cartridge almost since the .270 itself was introduced. That dream was realized with the introduction of the 6.5mm Rem. Magnum. The case capacities of the two cartridges are just about identical and, unlike the newer .270 WSM, the 6.5mm Magnum does not require a super-fat case with a rebated rim that reduces magazine capacity and raises questions about feed reliability.
The 6.5mm Remington Magnum
The 6.5mm Magnum was introduced by Remington in 1965 as a companion cartridge to the .350 Remington Magnum, introduced the previous year in the new and radical Model 600M bolt action carbine. The 6.5mm Rem. Mag. thus became the second short action (.308 length) magnum cartridge in the world. The Model 600 was the forerunner of today's lightweight, short magnum rifles, but neither the rifle nor the cartridges it fired were much appreciated in the 1960's. They were too far ahead of their time.
The 6.5mm Magnum case is simply the belted, bottleneck, .350 Magnum case necked-down to accept 6.5mm (.264" diameter) bullets. Both were based on a shortened version of the popular 7mm Remington Magnum case. The shoulder angle is 25 degrees, the rim diameter is the magnum standard .532", and the overall case length is 2.17". Cartridge overall length (COL) is 2.8".
The reborn 6.5mm Magnum is initially being offered in the Remington Model 673 Guide Rifle, again a companion to the .350 Magnum cartridge for which the Guide Rifle was designed. Since it will fit in any short action magnum rifle, I hope that it will also be offered in the Model 7 Magnum rifle, and in other rifles chambered for the WSM and Remington SAUM line of cartridges.
The Remington factory load for the 6.5mm Mag. drives a 120 grain PSP Core-Lokt bullet at a muzzle velocity (MV) of 3210 fps and muzzle energy (ME) of 2744 ft. lbs. In the 1960's shooters with access to chronographs found that the cartridge did not live up to its paper ballistics, particularly in the short 18.5" barrel of the Model 600M carbine. The 2004 load takes advantage of modern powders and Model 673 rifles come with 22" barrels, so real world performance should be much closer to the claimed ballistics.
Reloaders relying on canister powders will have a hard time duplicating the ballistics of the factory load, but do have access to a much greater variety of bullet weights. While the 120 grain 6.5mm bullet is a good choice for CXP2 class game, especially deer and antelope at long range, a 129-130 grain bullet is probably a better all-around choice, and a 140 grain bullet is the ticket for heavier CXP3 class game.
The sixth edition of the Hornady Handbook of Cartridge Reloading lists full power loads with their 129 grain bullets at a MV of 3000 fps and full power loads with their 140 grain bullets at 2900 fps. For more information on the 6.5mm Magnum see my article "The 6.5mm Remington Magnum" on the Rifle Cartridge Page.
The .270 Winchester
Winchester introduced their famous .270 in 1925. At the time it was the flattest shooting factory loaded cartridge in the U.S., a title it retained for many years. It is one of the premier all-around big game hunting cartridges, and it made my short list of the top four such cartridges. (See my article "All-Around Rifle Cartridges" for more on that.)
The .270 is based on the .30-06 case simply necked down to accept .277" diameter bullets. The .270's shoulder angle is 17.5 degrees, the rim diameter is .473", the overall case length is 2.54", and COL is 3.34".
Almost every gun maker who builds an action suitable for the .270 Winchester offers the cartridge. In the U.S. these include Browning, Remington, Ruger, Savage, Weatherby, Winchester and others.
There is a large number of .270 factory loads from all major ammunition manufacturers. The most typical U.S. factory loads drive a 130 grain bullet at a MV of 3060 fps, 140 grain bullets at a MV of 2920-2960 fps, and 150 grain bullets at a MV of 2800-2900 fps.
Reloaders can duplicate all of these loads and the selection of .277" bullets is huge. A 130 grain bullet is most often chosen for hunting CSP2 class game, and the 150 grain bullet is the favorite for hunting heavy CXP3 class game. For more details, see my article "The Great .270 Winchester" on the Rifle Cartridge Page.
For the purposes of this article I am going to compare two of the most typical loads for each cartridge. The figures for the 140 grain bullet for the 6.5 Mag. represent a handload taken from the Hornady Handbook; all other figures are for standard factory loads. There are other bullet weights for both cartridges, but these are popular choices. The selected loads are (caliber, bullet, MV, ME):
In the course of this article we will compare energy, trajectory, sectional density, bullet frontal area, killing power, recoil and availability. And we will end with a look at the suitability of these loads for their intended purpose of big game hunting.
Kinetic energy is important because it is a measure of the amount of work (i.e. destruction) of which each cartridge is capable. It is energy that powers such important functions as bullet expansion, penetration, and tissue destruction. Following are the energy figures in foot-pounds for each of our selected bullet weights at 100, 200, and 300 yards.
As can be seen from these figures, the higher velocity of the 6.5mm Magnum loads results in slightly higher energy figures compared to the equivalent .270 loads, but the difference is unlikely to be of great significance in the field. Either is more than sufficient to bowl over deer and antelope at 300 yards, which is about the limit of these cartridges' maximum point blank range (MPBR) and most hunters' ability to keep their bullets in the kill zone.
Here are the trajectory figures in yards for our selected loads. For comparison, the zero range is 200 yards in all cases:
The maximum point blank range (MPBR) of both cartridges is around 300 yards for big game hunting. The 6.5mm Magnum has a slight advantage in trajectory when comparing the equivalent bullet weights for each caliber. At 300 yards the 120 grain 6.5mm bullet has 0.6" less drop than the 130 grain .270 bullet, and the 140 grain 6.5mm bullet has 1.4" less drop than the 150 grain .270 bullet at the same distance.
Sectional Density (SD) is essentially the ratio of a bullet's weight to its diameter. SD is an important factor in penetration, as a long slender bullet of a given weight penetrates better than a short fat bullet of the same weight, other factors being equal. The higher the SD, the better the potential penetration. Here are the SD figures for our selected bullet weights in both calibers.
For CXP2 class game an ideal SD would be about .225 or better. The 120 grain 6.5mm and 130 grain .270 bullets handily exceed that number. For large CXP3 class game a SD of about .247 or greater is preferred, and again the heavier bullets for both the 6.5mm and .270 are well above the minimum, with the 140 grain 6.5mm bullet having the best SD in the group. These favorable SD numbers help to explain why the 6.5 and .270 cartridges are known for their excellent killing power.
From the numbers above we can conclude that, in terms of SD, the 120 grain 6.5mm and 130 grain .270 bullets are suitable for all CXP2 class big game. The 140 and 150 grain bullets in their respective calibers offer the potential penetration required for large CXP3 class game.
Bullet frontal area
Frontal (cross-sectional) area plays a significant role in killing power. Clearly, the bigger the hole you punch in an animal, the greater the potential damage. The length and diameter of the wound channel are the critical factors in killing power. Obviously, a .277" diameter (.270 caliber) bullet is fatter than a .264" diameter (6.5mm caliber) bullet. The frontal area of a .264" bullet is .0547 square inches. The frontal area of a .277" bullet is .0603 square inches. This is an advantage that favors the .270 with all bullet weights.
Killing power is the most difficult factor to quantify. Bullet placement is by far the most important factor in a cartridge's effectiveness on game, and that is a function of the hunter's skill, not the cartridge used. The construction and performance of a hunting bullet is also very important, and practically every type of hunting bullet is available (at least to reloaders) for either the 6.5mm Magnum or the .270. Kinetic energy is one indication of potential killing power, as are bullet frontal area and sectional density, but none of these tells the entire story.
One attempt to include all of the relevant factors (aside from bullet placement, which is assumed to be adequate) is the Optimum Game Weight (OGW) formula developed by Edward A. Matunas and published in the Lyman 47th Reloading Manual. Here are the OGW figures in yards for typical 6.5mm Rem. Mag. and .270 Win. big game loads. (For more on OGW, see my "Expanded Optimum Game Weight Table" on the Tables, Charts, and Lists Page.)
These OGW figures show that, when comparing the 120 grain 6.5mm and 130 grain .270 loads, there is no practical difference in killing power. Comparing the 140 grain 6.5mm load to the 150 grain .270 load reveals that the two are within 1 pound in OGW at 100 yards. Only at 300 yards does the 140 grain 6.5mm bullet eke out a modest 66 pound advantage in OGW over the 150 grain .270 bullet.
These figures tend to confirm that the small differences we have observed in energy and sectional density in favor of the 6.5mm Magnum are largely negated by the .270's advantage in bullet cross-sectional area.
Recoil is an important factor because anyone can shoot better with a gun that kicks less. Remember that shot placement is the most important factor in killing power, so differences in recoil matter. Guns that kick less are more fun to shoot and generally get used more. And practice makes perfect, as the old saying goes. Here are recoil energy figures for our selected loads for both calibers in 8 pound rifles (taken from the Remington Shoot! program).
These figures are approximate, but it is clear that the .270 kicks a little harder than the 6.5mm Rem. Mag. The technicians at Remington estimate that recoil above 15 ft. lbs. is excessive, at least for the majority of shooters. That is exactly the same figure that I have arrived at based on my own experience and observations. The .270 isn't too far above the 15 ft. lb. figure, but it is over the line.
Availability of guns and ammunition
The biggest difference between the .270 Winchester and the 6.5mm Remington Magnum is not to be found in ballistics or killing power, but in the availability of rifles and ammunition. In this area the .270 has a big advantage. Almost every manufacturer who builds a rifle that can handle the .270 chambers for it. The selection is broad and includes all types of rifles including bolt, lever, pump, autoloading, single shot, and double barrel designs. In Europe even drillings (three barrel rifle/shotgun combinations) are chambered for the .270 Winchester.
Naturally, .270 ammunition is sold just about everywhere in the world that centerfire rifle ammunition of any type is available. The .270 is recognized as one of the truly great all-around hunting cartridges.
The situation is much different for the 6.5mm Remington Magnum. At least initially, only the Remington Model 673 rifle is to be chambered for the reintroduced cartridge. This is a bolt action rifle with a 22" barrel, a blue metal finish and a laminated stock. As I write these words there are no other choices. If you like the Model 673 rifle (I do, I own one), fine. If not, you are out of luck. Clearly Remington needs to offer the 6.5mm Magnum in the short action Model 7 Magnum rifle and the short action versions of their Model 700 rifles. If 6.5mm Magnum rifles begin to sell for Remington, it is probable that other manufacturers will pick-up the cartridge.
The ammunition situation is equally restrictive. Remington offers exactly one factory load in 6.5 Magnum, using their excellent 120 grain Core-Lokt bullet. A 140 grain factory load is a practical necessity, so I hope that it is forthcoming soon. But for now it would be very advantageous for the 6.5mm Magnum owner to be a reloader.
The silver lining to this clouded situation is that Remington rifles and ammunition are very widely distributed, at least in North America. Any Remington dealer should be able to order a Model 673 rifle and 6.5mm Rem. Mag. ammunition, once the pipeline is filled, even if they don't have it in stock.
Big game hunting
The .270 Winchester and 6.5mm Remington Magnum were both designed specifically as hunting cartridges. As we saw in the section on killing power, both are capable of taking all CXP2 class big game within their maximum point blank range of approximately 300 yards with any of our selected loads.
In North America that includes such animals as pronghorn antelope, the various deer species, goats, sheep, and feral hogs. Even very large examples of these creatures seldom exceed 300 pounds on the hoof, and they average less than 200 pounds. Using the heavier 140-150 grain bullets, either caliber is a reasonable choice for CXP3 class game out to at least 100 yards.
The 6.5mm Remington Magnum and .270 Winchester are both fine hunting cartridges with nearly identical capabilities. Ballistically, either is a fine combination long range and all-around cartridge.
The .270 and the 6.5mm Magnum offer as much killing power and maximum point blank range as most shooters can take advantage of. There are flatter shooting cartridges in the world, but the average hunter simply cannot shoot well enough from field positions to take advantage of them. And those cartridges, of necessity, burn more powder and kick harder without conferring any real world advantage.
I am convinced that this balance of very flat trajectory, good killing power, and tolerable recoil is the secret behind the great .270 Winchester's success. The 6.5mm Remington Magnum combines exactly the same virtues in a strong, reliable, short action case. I hope that, this time around, shooters appreciate what Remington has made available to them.
Copyright 2003, 2012 by Chuck Hawks. All rights reserved.