Compared: The 6.5x55 SE and 6.8mm Rem. SPC
By Chuck Hawks
Both the 6.5x55 SE and 6.8mm Remington SPC were developed as military cartridges. Both were almost immediately adapted to sporting purposes, both hunting and target shooting. Their purpose and capabilities are fairly similar, but their commercial history is very different--if a cartridge as new as the 6.8mm SPC can be said to have a history at all.
While at this writing the 6.8mm SPC is brand new, the venerable 6.5x55 is now well over 100 years young, and recognized as one of the world's great hunting cartridges. The new 6.8mm cartridge shows promise; the old 6.5mm cartridge has already fulfilled it.
Because they are both successful military developments of similar caliber, and because they were both immediately adapted to sporting pursuits, comparisons seem almost inevitable. And because one is a 2004 introduction and the other an 1894 introduction it will be interesting to see just how far we have come in 110 years.
The 6.5x55 SE
The 6.5x55 was adopted as the service cartridge of Sweden and Norway in 1894. It subsequently become a very popular sporting cartridge in Scandinavia and eventually caught on in the rest of the world, including North America. In the U.S. it is known as the "6.5x55mm Swedish Mauser" or just the "6.5mm Swede."
The 6.5x55 is one of those fortunate few cartridges that is exceptionally well balanced. Despite its age, the 6.5x55 is a modern looking rimless cartridge with a sharp 25 degree shoulder angle and the case and neck length to allow it to efficiently handle long, heavy bullets.
Most ammunition manufacturers load for the 6.5x55. Typical U.S. factory loads for the 6.5x55 drive a 139-140 grain bullet at a muzzle velocity (MV) of 2550-2600 fps. Higher performance Light Magnum loads from Hornady advertise a 129 grain bullet at a MV of 2770 fps and a 140 grain bullet at a MV of 2740 fps.
Norma of Sweden offers a 139 grain bullet at a MV of 2854 fps, a 140 grain bullet at a MV of 2789 fps, and several different 156 grain bullets at MV's ranging from 2526 fps to 2644 fps. RWS of Germany offers several 6.5x55 loads including a 127 grain bullet at a MV of 2850 fps and a 154 grain bullet at a MV of 2670 fps. Sellier & Bellot of the Czech Republic loads a 140 grain PSP bullet at a MV of 2645 fps. These are typical of European 6.5x55 loads, which on average are loaded to higher pressure than U.S. factory loads.
Reloaders with old military rifles can safely achieve velocities similar to the standard U.S. factory loads. In the U.S. the maximum average pressure (MAP) for the 6.5x55 is held to only 46,000 psi, but reloads for modern rifles such as the Ruger M77 and Winchester Model 70 can safely be taken to 50,000 cup. This allows reloaders with modern rifles to equal and sometimes exceed the European factory loads.
In the U.S., Dakota, Ruger and Winchester chamber their rifles for the 6.5x55. In addition Blaser, CZ, Howa, Sako, Sauer, and Tikka offer 6.5x55 rifles for sale in the U.S. market. These and other makes are available in Europe.
The 6.8mm Remington SPC
This new 6.8x43mm (.270 caliber) cartridge is the result of at least a two year cooperative effort between Special Operations, the Army Marksmanship Unit, and Remington. The old .30 Remington was chosen as the basic case from which the new cartridge would spring, as its rim size required only minimal modification to the M16's bolt face.
Following typical modern procedure, the .30 Rem. case was shortened (to a length of 43mm), blown out, necked-down to accept .277" diameter bullets, and given a sharper shoulder and a shorter neck. The resulting cartridge will function properly in an M16 length action and magazine.
Remington is offering four 6.8mm factory loads, all with 115 grain bullets. These include two target loads, a hunting load with a new Core-Lokt Ultra bonded bullet, and a Metal Case military-type load. The initial factory loads all have a muzzle velocity (MV) of 2800 fps and a muzzle energy (ME) of 2002 ft. lbs. from a 24" test barrel. These figures are taken from Remington's 2004 catalog.
I can understand why Remington is introducing the 115 grain MC military-type load, but I fail to understand why they do not offer a 100 grain varmint/predator load using their Pointed Soft Point bullet. I would think that a 100 grain bullet could be driven at a MV of about 3000 fps.
As most reloaders know, 115 grains is not a traditional weight for .277" bullets. Typical CXP1 (varmint) bullets for .270 caliber rifles weigh 90-110 grains. Typical bullets for CXP2 class game (deer and antelope) weigh 120-140 grains. The 120 grain Barnes X-Bullet should represent just about the optimum weight for hunting deer, antelope, sheep, and goats given the case capacity of the 6.8mm SPC.
As of this moment Remington has not announced any rifles chambered for the new 6.8mm cartridge, nor has anyone else. But this is sure to change; a new U.S. Army cartridge will not be overlooked by rifle or ammunition manufacturers.
I see the new cartridge as being most suitable for use in autoloading, pump, and bolt action rifles. It should play a role in tactical, target and hunting applications and be chambered in rifles of all three types. For hunters, lightweight bolt action rifles such as the Remington Model 7 and Model 700 Mountain Rifle would seem to be a natural home for the 6.8mm SPC. It should serve quite well for both the deer hunter and the mountain hunter.
For the purposes of this article I am going to compare three typical loads for each cartridge. These will consist of a lightweight varmint bullet, a general purpose medium weight bullet, and a heavier bullet suitable for hunting CXP2 class (and possibly larger) game.
For the 6.8mm SPC the bullet weights will be 100 grains (varmint), 115 grains (general purpose), and 120 grains (big game hunting). For the 6.5x55 the three bullet weights will be 100 grains (varmint), 129 grains (general purpose), and 140 grains (big game hunting). Factory loads and full power handloads (where applicable) will be deemed typical.
The figures for the 6.8mm, 115 grain bullet that follow are taken from the Remington Metal Case factory load; the figures for the 100 and 120 grain bullets are estimated to be representative handloads for those bullet weights in the new cartridge. The Hornady 100 grain Spire Point and Remington 115 grain MC bullets used in the following comparisons are pointed flat-base bullets, the 120 grain Barnes X-Bullet is a pointed boat-tail.
The figures for the 100 grain 6.5mm load are taken from the Sixth Edition of the Hornady Handbook of Cartridge Reloading and premium Hornady factory loads represent the other two bullet weights. All three of these Hornady bullets are pointed flat-base bullets. The selected loads are (caliber, bullet, MV, ME):
In the course of this article we will compare velocity, ballistic coefficient (BC), trajectory, energy, sectional density (SD), bullet frontal area, killing power, and recoil. And we will end with a look at the suitability of these loads for varmint and big game hunting.
Velocity is important because the faster a bullet flies the less time gravity has to work on it before it hits the target. Thus bullet drop is reduced or, as riflemen say, the cartridge shoots flatter.
As can be inferred from the numbers above, the velocity of the two cartridges is similar, but the 6.5x55 does have an advantage whether comparing bullets of similar weight or similar SD. For example, it can drive a 120 grain bullet to a MV of 2800-3000 fps. This is due to its larger case and consequent greater powder capacity. Ultimately, as the car guys say, "there is no substitute for cubic inches." If velocity is the criteria, with bullets of similar weight or bullets of similar SD, the 6.5x55 is the winner.
BC is a measure of how efficiently a bullet flies through the air. The lower the air drag the higher the BC. If two bullets have the same construction and form, the longer (heavier) or skinnier (smaller caliber) contender will have the higher BC. Here are the ballistic coefficients for the bullets used in this comparison.
The higher the BC the slower the bullet sheds velocity. It will exhibit less drop and less wind drift downrange. Because 6.5mm bullets are slightly smaller in diameter than 6.8mm bullets (.264" compared to .277"), and typically weigh the same or more, they will generally have a superior BC. The advantages of superior BC are most apparent at long range. This gives the 6.5x55 an advantage for long range shooting.
Here are the trajectory figures in yards for our selected loads. For comparison, the zero range is 200 yards in all cases:
The 6.5x55 has a slight advantage in trajectory, averaging about 1" less drop at 300 yards and over 3" less drop at 400 yards. For instance, at 300 yards the 100 grain 6.5mm bullet has exactly 1.0" less drop than the 100 grain 6.8mm bullet, and at 400 yards it has 3.2" less drop. It is fair to conclude that the 6.5x55 is the flatter shooting cartridge.
Kinetic energy is essentially a function of mass (bullet weight) times the square of velocity. It's important because energy 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 and greater bullet weight of the 6.5x55 loads pays off in higher energy figures compared to equivalent 6.8mm SPC loads. It is worth noting the old rule of thumb that an effective deer cartridge should deliver at least 800 ft. lbs. of energy at impact. In this case, both cartridges exceed that energy level at 300 yards, which is beyond the maximum point blank range of both. For heavier game at closer range the additional energy of the 6.5x55's big game bullets should give it the edge.
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 number, the better the potential penetration and the longer the wound channel. 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 6.8mm bullet barely qualifies, and the lighter 115 grain "general purpose" bullet falls well short of what would normally be considered acceptable. It is fair to say that the 6.8mm Remington SPC comes up a short in terms of SD and potential penetration.
On the other hand, a 120 grain 6.5mm bullet has a SD of .246 and the SD of the 129 grain 6.5mm bullet slightly exceeds the SD of a 140 grain 6.8mm bullet (.261). For large CXP3 class game a SD of about .247 or greater is preferred, and the 129 grain bullet exceeds that figure as well, making it a good choice for mixed bag hunts.
The 140 grain 6.5mm bullet has the best SD in the group and has proven to be a deep penetrator in large, heavy animals. Given adequate bullet placement the 140 grain 6.5x55 bullet has accounted for more than its share of outsized animals such as moose and polar bear. Beasts of this size are well beyond the capability of the 6.8mm SPC except under the most favorable circumstances. The excellent SD numbers and consequent deep penetration of its bullets helps to explain why the 6.5x55 is known for its excellent killing power.
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 diameter of the wound channel is an important factor in killing power.
Obviously, a .277" diameter (6.8mm) bullet is fatter than a .264" diameter (6.5mm) 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 the one factor that favors the 6.8mm SPC with all bullet weights.
Killing power is the most difficult factor to quantify. 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.
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 6.8mm SPC or the 6.5x55, although some of the best .277" bullets are too long for the short 6.8x43mm case.
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 is the maximum optimal distance in yards for taking 200 pound and 400 pound animals with our selected 6.8mm Rem. SPC and 6.5x55 SE 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 while the 120 grain 6.8mm bullet is somewhat superior to the 115 grain bullet on 200 pound game, neither is close to either of the 6.5mm bullets in killing power. The mighty 140 grain 6.5x55 bullet can take 400 pound game at well over 7 times the distance of either 6.8mm SPC bullet. These figures tend to confirm that the 6.5x55's advantage in every category above save bullet cross sectional area do, in fact, translate to greater killing power.
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.
Both of these calibers are relatively light kickers. A 7.5 pound 6.5x55 rifle generates about 11.8 ft. lbs. of recoil when shooting a 129 grain bullet at a MV of 2770 fps. The 6.8mm SPC delivers an estimated 9.1 ft. lbs. of free recoil energy shooting a 120 grain bullet at a MV of 2700 fps in a 7.5 pound rifle. The greater power of the 6.5x55 downrange also means greater power at the shoulder.
The technicians at Remington estimate that recoil above 15 ft. lbs. is excessive, at least for the majority of shooters. That squares with my own observations. Fortunately, both of these calibers are well below the 15 ft. lb. figure.
Big game hunting
The 6.8mm Remington SPC and 6.5x55 SE were both designed as military cartridges, but both were immediately adapted to recreational shooting pursuits. Deer are the most important and sought after big game animals in North America, and all varieties average less than 200 pounds on the hoof. So do the various species of sheep and goats. Pronghorn antelope probably average closer to 100 pounds. Using appropriate bullets, either caliber is a reasonable choice for all of these CXP2 class creatures out to its 270 yard (approximate) maximum point blank range.
Neither caliber is really ideal for large CXP3 class animals, but the 6.5x55 has proven adequate for very large animals in the hands of a hunter who can put its bullets into a vital spot. The 6.8mm SPC is not a good choice for sport hunters seeking elk and other large game.
Clearly, in terms of ballistics, medium-caliber military cartridges have not gained anything in the last 110 years, although the rifles that shoot military cartridges have changed greatly, and this has influenced cartridge design. Regardless, the 6.8mm SPC and 6.5x55 are both fine medium range, medium game hunting cartridges.
The 6.8mm SPC and 6.5x55 offer as much killing power and range as most shooters need. Both are very accurate cartridges suitable for long range rifle competition as well as hunting. The 6.8mm Remington SPC is a deer and mountain rifle cartridge featuring very light recoil. And the more powerful 6.5x55 SE remains one of the most pleasant shooting, all-around, big game hunting cartridges.
Copyright 2004, 2012 by Chuck Hawks. All rights reserved.