Compared: The 6.5mm Grendel and 6.5x55mm SE
By Chuck Hawks
The 6.5mm Grendel is a new military cartridge designed for the AR-15 rifle platform, while the 6.5x55 SE (Swedish Mauser) is a very old military cartridge designed for use in bolt action rifles that was almost immediately adopted for civilian use. For over 100 years the 6.5x55 has proven to be suitable for both formal target shooting and hunting a wide variety of game animals around the world. Because of this, although it was replaced for military use many years ago, the 6.5x55 has remained popular and in demand. This article compares these two 6.5mm entries, one new and one old, as big game hunting cartridges.
The 6.5mm Grendel was designed as a cartridge for long range precision shooting with AR-15 type rifles. Bill Alexander of Alexander Arms developed this short, squat 6.5mm cartridge and Alexander Arms is now offering ammunition and rifles in 6.5mm Grendel caliber. Unfortunately, these are military style match/sniper rifles on the AR-15 platform, which are of limited utility to mainstream hunters and shooters.
Alexander tried a variety of calibers for his new cartridge. The .264" (6.5mm) caliber was eventually chosen due to the availability of suitable bullets (in terms of weight and length) that were compatible with the restricted length of the AR-15 magazine. As the model for case design, Alexander chose the 6mm PPC bench rest cartridge, necked-up to accommodate standard .264" diameter bullets. Lapua engineers assisted Alexander with modifications intended to optimize the case for use with 107-130 grain bullets, which included a longer shoulder and a shorter neck, but the PPC's basic short, fat case shape was retained.
Most of the 6.5mm Grendel's case dimensions remain similar to those of the parent PPC case. Capacity is about 35 grains of water. Cartridge overall length is 2.255" and bullet diameter is .264" (6.5mm). MAP is about 42,000 psi.
The claimed muzzle velocity (MV) with 120 grain bullets is 2600 fps. Bill Alexander fired 120 grain Nosler Ballistic Tip hunting bullets at a MV of 2600 fps into blocks of ballistic gelatin 300 yards distant, with encouraging results. He reported that the Nosler bullets penetrated 18" and expanded to .51 caliber while retaining 75% of their weight. Long experience with previous 6.5mm rifle calibers has shown that a 120 grain hunting bullet at a MV of 2600 fps is satisfactory for CXP2 class game.
Alexander Arms offers 6.5mm Grendel ammunition factory loaded with 90 grain Speer TNT varmint bullets, Nosler 120 grain Ballistic Tip hunting bullets and Lapua 123 grain Scenar match bullets. This ammunition is loaded using Lapua brass with an Alexander Arms head stamp. It is the load using the Nosler 120 grain BT bullet that concerns us here. For handloaders, Alexander Arms also offers 6.5mm Grendel reloading dies made by Lee Precision.
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 CZ, Ruger 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.
Blaser, CZ, Dakota, Howa, Ruger, Sako, Sauer and Tikka offer 6.5x55 rifles for sale in the U.S. market and Winchester used to offer their fine Model 70 Classic Featherweight in the caliber. These and other makes are available in Europe.
Since only one hunting load is offered for the 6.5mm Grendel, using a 120 grain Nosler Ballistic Tip bullet at a MV of 2600 fps, that is the load we will compare. For the 6.5x55 there are a great many available factory loads using bullet weights ranging from 90-160 grains. However, 140 grain bullets are by far the most popular choice for the cartridge, so that is what we will use. To represent the 6.5x55 we will use the Norma (Swedish) factory load with a 140 grain Nosler Partition bullet at a MV of 2789 fps. Nosler bullets are widely available to handloaders, who can duplicate the ballistics of these factory loads in their reloads.
We will compare these 6.5mm Grendel and 6.5x55 SE factory loads in velocity and energy, sectional density (SD), trajectory, killing power, recoil and the availability of both guns and ammunition. (Since both are 6.5mm cartridges using standard .264" diameter bullets, the cross-sectional area is the same for both cartridges and no comparison of that feature is necessary.) At the end will be a few concluding comments.
Velocity and Energy
Higher velocity means flatter trajectory, given bullets of similar ballistic coefficient. This makes accurate bullet placement easier downrange. Velocity is also the most important component in the formula used to compute kinetic energy.
Kinetic energy is a measure of the ability to do work and it is widely used to compare the power of rifle cartridges. Energy powers bullet penetration and expansion, which are very important elements in killing power. The key factors in computing kinetic energy are bullet mass and the square of bullet velocity.
Here are the Alexander Arms velocity/energy figures in feet-per-second / foot-pounds for the 120 grain Ballistic Tip bullet in the 6.5mm Grendel:
And here are the Norma velocity/energy figures for the 6.5x55's 140 grain Nosler Partition factory load:
These numbers make it obvious that the 6.5x55 is a much more powerful cartridge than the 6.5mm Grendel. This figures, as it is based on a larger case that can hold more propellant. Furthermore, in modern rifles the 6.5x55 can be safely loaded to higher pressure than the 6.5mm Grendel. These factors give the 6.5x55 a big advantage in performance.
As a rule, you want to retain at least 800 ft. lbs. of energy at bullet impact when hunting CXP2 game. The energy figures show that the 6.5mm Grendel is adequate for the purpose past 300 yards and the 6.5x55 is considerably better. In terms of energy, a load that can deliver a hunting weight bullet with a sectional density (SD) in excess of .250, carrying over 1200 ft. lbs. is generally considered adequate for the common CXP3 game species, such as Rocky Mountain elk. While the 6.5mm Grendel fails to meet this requirement, the 6.5x55 does so handily.
Sectional density is important because, other things being equal (impact energy, bullet construction, etc.), the bullet with the higher SD penetrates deepest. To kill cleanly, the bullet must penetrate into the animal's vitals.
Here are the sectional densities of the bullets used in our selected factory loads:
Both SD figures are very good for CXP2 game, where extreme penetration is seldom required. SD's as low as .205 are usually considered satisfactory and SD's of .225 or greater are ideal. The .287 SD of the 6.5x55's bullet is excellent, even for heavy (CXP3) game, so the 6.5x55 clearly has the advantage in terms of SD. Because it also has an advantage in impact energy to drive that bullet deep into the animal, we can safely assume that it has the potential for superior penetration in the field.
The greater SD of the 140 grain bullet is augmented by the construction of the Partition bullet. The internal partition separates the expanding front half of the bullet from the part behind the partition. This rear portion of the Partition bullet retains 100% of its original weight and acts like a solid, assuring adequate penetration even in tough, big-boned game. The Ballistic Tip is known as a "soft" bullet that tends to expand quickly and shed weight rapidly, limiting its total penetration. Such bullets do, however, tend to kill CXP2 game quickly.
Trajectory is important to hunters because the flatter a bullet's trajectory, the easier it is to achieve accurate bullet placement at long and unknown ranges. The primary factors influencing trajectory are bullet velocity and ballistic coefficient (BC). In the case of the cartridges compared here, Nosler quotes a .458 BC for the 120 grain Ballistic Tip and a .490 BC for the 140 grain Partition. Because the 6.5x55 is superior in both, we can assume that it will shoot flatter than the 6.5mm Grendel. The question is, how much flatter?
The best way to compare the trajectory of hunting loads is by their maximum point blank range (MPBR). MPBR is the distance at which the bullet drops 3" below the line of sight and represents the longest range at which shots at big game animals should be taken. Here is the MPBR based trajectory of our comparison loads from 100 to 300 yards when fired from a rifle with a telescopic sight mounted 1.5" over the bore.
Once again in this comparison, the 6.5x55 is the decidedly superior cartridge, with a 19 yard MPBR advantage. It shoots flatter and thus has a considerable advantage in practical accuracy. (The ease with which you can place your bullet accurately in the field for a quick kill.)
Killing power is the most difficult factor to estimate, as there is no scientific formula to apply. Systems have been created to estimate killing power (including one by yours truly), but none of them should be regarded as particularly reliable and many such systems have no correlation with reality at all.
One of the better ways to estimate killing power, in my opinion, is the Optimal Game Weight (OGW) formula devised by Edward A. Matunas. It at least attempts to balance some of the major variables involved, rather than being based entirely on energy, momentum or whatever. OGW attempts to relate killing power to the live weight of game animals, a very useful notion. Since the 6.5x55 and 6.5mm Grendel are both primarily CXP2 game hunting cartridges, we will compare the OGW of the factory loads for the two calibers at the muzzle and at the maximum distance at which they are optimum for killing 200 pound game and at the muzzle. Here are the OGW numbers.
These OGW numbers illustrate the 6.5x55's huge advantage in killing power. Since clean kills are the mantra of the ethical hunter, there is no question that it is the superior cartridge in the field.
Recoil Energy and Velocity
How hard a rifle/cartridge combination kicks is of crucial importance in the field, as recoil degrades the shooter's ability to place his or her bullet accurately. If a rifle kicks hard enough to cause the shooter to flinch, accuracy goes out the window and the result in the field is almost certain to be a missed (or much worse, wounded) game animal. Bullet placement is, by far, the most important factor in killing power. Here are some approximate recoil energy (in foot pounds) and velocity (in fps) figures for our comparison loads when fired in rifles of normal weight for their respective cartridges.
These numbers show that the 6.5x55 kicks about 60% more (in terms of energy) than the 6.5mm Grendel with our comparison loads. This is a significant difference to a recoil sensitive shooter and a noticeable difference to any shooter. However, both cartridges/loads are below the 15 ft. lb. level that an "average" hunter might consider comfortable and in reality the 6.5x55 has a reputation as a soft shooting cartridge. However, the 6.5mm Grendel has a big advantage in lower recoil over the 6.5x55 and that might make it the better choice for the very recoil sensitive shooter/hunter. For comparison, the common .30-06/180 grain factory load generates recoil energy of about 20.3 ft. lbs. and a 12.8 fps recoil velocity in an 8 pound rifle. Compared to that, these are easy cartridges to shoot.
The 6.5x55mm SE has been around for a long time and ammunition for the cartridge is loaded by most of the major ammo suppliers in the world. This advantage should not be underestimated. On the other hand, if the 6.5mm Grendel is not picked up by a major ammunition supplier, its commercial failure will be guaranteed. No cartridge, regardless of its merits, can survive in the market place without a readily available source of ammunition. Any sporting goods dealer can stock 6.5x55 ammo if they choose to do so and those that don't keep it in stock can order it for their customers. The 6.5x55mm SE is a big winner in the ammo availability category.
As is the case with ammunition availability, rifle availability is crucial to the long term commercial success of any cartridge. If you can't find a rifle that shoots it, what good is the cartridge?
Alexander Arms, a small business, offers complete AR-15 style autoloading rifles in 6.5mm Grendel as well as complete upper receiver assemblies for other AR-15/M16 style rifles. They call one of their AR-15 clones the "hunter" model. It is supplied with a 19.5" barrel and a flat-top receiver and carries a MSRP of $1369. As far as I can determine, that is it for 6.5mm Grendel hunting rifles.
The 6.5x55 SE has been available in a variety of brands and models of hunting rifles for decades and new hunting rifles in the caliber are available from major manufacturers as I write these words. In addition, there are thousands of high quality, surplus Swedish Mauser military rifles available in the caliber that can be purchased at low cost and sporterized. Whether new or used, the 6.5x55mm SE wins the rifle availability part of this comparison hands down.
As you can see from the foregoing comparison, the 6.5x55 is far superior to the 6.5mm Grendel as a big game cartridge in every performance category except recoil. Actually, this is the most one-sided cartridge comparison I can remember writing. Fortunately, while the 6.5x55 kicks considerably harder than the 6.5mm Grendel, it is still a moderate recoil cartridge (below 15 ft. lbs.), much more comfortable to shoot than cartridges in the "all-around" .270 and .30-06 class. The 6.5x55 SE is one of the best moderate recoil cartridges, treading close on the heels of the all-around cartridges in performance.
For the shooter who absolutely has to hunt with an AR-15 type rifle, the 6.5mm Grendel is one of the better cartridge choices. For everyone else, there are plenty of better hunting cartridges on the market and the 6.5x55 SE is prominent among them.
Copyright 2009, 2012 by Chuck Hawks. All rights reserved.