John Hanka
February 22, 2005
Being a military buff, I’m always asking myself questions such as: What’s the best main battle tank? What’s the best jet fighter? What’s the best assault rifle? And then there came the day when I asked myself: What’s the best assault rifle cartridge? After studying the issue for a while and giving it quite a bit of thought, I typed into Google’s search engine: 6.5 PPC. The search results lead me to Arne Brennan’s early website describing his experiments with the 6.5 PPC which, in collaboration with Bill Alexander of Alexander Arms, was to become the 6.5 Grendel.
Subsequently, I created this website and began my online advocacy of the 6.5 Grendel as a general-purpose military cartridge for assault rifles, man-portable machine guns, and designated marksman rifles for ranges from zero to 1,000 yards and as a replacement for both the 5.56 NATO and 7.62 NATO. In response to a challenge on another forum, I had set down my thinking on the issue in a somewhat orderly fashion, and have reproduced those basic arguments here for your consideration.
First of all, what do I actually propose? I contend the 6.5 Grendel should replace both 5.56 and 7.62. I propose a three-cartridge small arms system: (1) A pistol cartridge for pistols and submachine guns. (2) The 6.5 Grendel for assault rifles, man-portable machine guns (includes what we now call LMGs and MMGs), and designated marksman rifles. (3) Vehicle mounted and heavy anti-material would be handled by .50 BMG. Dedicated snipers with very specific needs can use any cartridge/weapon combo they’re willing to lug into the field. Now, if this proposal seems radical, consider that that is how we fought World War II. We had the .45 ACP for pistols and SMGs, the .30-06 for rifles and machine guns, and the .50 BMG. Now, of course, we had the .30 Carbine, but that was intended to be a pistol replacement, and not a general-purpose rifle cartridge. I’m proposing the 6.5 Grendel as a new general-purpose rifle cartridge.
I base my advocacy of the 6.5 Grendel roughly on the military studies coming out of World War II that the .30-06 was too heavy and the ideal small-arms cartridge should be something like the British .280. My thinking is based on acceptance of the general consensus of the postwar studies by the major participants, including the thinking that gave the Russians their 7.62x39 M1943. I accept the assumption that 99% of infantry firefights take place within 500 meters, and probably 85% take place within 300 meters. I still want a realistic long-range capability, however, for DMRs and the machine guns. And I don’t think the need for true long-range capability is in dispute, even given the above assumptions, because, for whatever reasons, the current U.S. military requirement includes 800-meter effectiveness, or more.
My proposal rests on the assumption that the current two-cartridge system is more by accident than by any master plan. It may actually have turned out well, and we’re getting along nicely with it, but it’s not absolutely dictated by any combat requirements that a military must have a two-cartridge shoulder arms system! So I consider it up for reasonable debate.
My proposal assumes that a one-cartridge system will have big-picture pay-offs in the realms of logistics and budgets. No more designing two sets of every weapon: a SCAR-L and a SCAR-H, a Mk 11 and a Mk12, an M249 and an M240, etc. No more worrying about whether you brought enough 7.62; everybody uses one cartridge, and this is helpful in a pinch. At this point, you might argue that the Russians, even in the heyday of their 7.62x39, maintained their 7.62x54 for the medium machine gun. I will grant this is a good point. However, the 7.62x39 never had ballistics that could equal those of their full-power cartridge; the 6.5 Grendel changes all that, shooting as flat, or flatter, than both 7.62 NATO M80 ball and M118LR!
It rests on the assumption that if 5.56 terminal ballistics are “good enough,” then 6.5G terminals also are. Moreover, any increase in terminal effect of the 6.5G over 5.56 is, as they say, “gravy.” The 6.5G hits with roughly twice the lead mass of 5.56, so you have the potential for twice the mass of fragments and, if maximum fragmentation is coincident with maximum temporary cavity, you’re going to have very convincing terminal effects. And the short answer to concerns about overpenetration before yaw is that, firstly, there’s more than one theory of where, exactly, a bullet should begin yaw in gelatin and, secondly, a new bullet can be engineered to specific requirements, if a given off-the-shelf bullet doesn’t happen to be ideal. This is what Hornady did with their 6.8 115gr OTM, for example.
It assumes that we don’t call upon 7.62 NATO weapons to improve soft-target terminal ballistics, we call upon them for increased range and penetration of intermediate barriers or light armor. I’m assuming that if 5.56 terminal effects in soft targets are “good enough,” then 7.62 terminals would be “overkill.” Thus, for 6.5G to replace 7.62, it doesn’t need to equal the soft-target terminal effects of 7.62, it needs to equal (or exceed!) the range and penetration of 7.62. If we truly felt 7.62 terminal effects were absolutely NEEDED across the board, we wouldn’t allow line units to be equipped with only 5.56! Nobody says, “Hey! My 5.56 isn’t lethal enough, bring in the 7.62s!” They say, “Hey! My 5.56 doesn’t have enough range or penetration, bring in the 7.62s.” You don't need a 7.62 MMG just to “keep their heads down”; you’ve got M249s for that. So if 6.5G can equal the range and penetration of 7.62, it’s a valid replacement, even if I’m replacing a 147gr bullet with a 123gr.
I am intrigued by the fact that we could give every troop in the line the range and penetration of 7.62 M80 in a compact cartridge that fits in the size envelope of 5.56 M855! Such an increase in firepower would definitely teach the enemy the difference between cover and concealment. And where the amount of effective cover is reduced on the battlefield, enemy casualties must increase. And where the enemy has been chased from cover that formerly stopped 5.56 and has been “herded” into available cover that can stop 6.5 Grendel with it’s ability to penetrate like 7.62 M80, a well-placed smart munition should be cost-effective.
All of cartridge design is a study in compromise. Alas, though there’s an increase in capability with an intermediate cartridge, there’s also a corresponding increase in weight; a basic load of 210 rounds of 6.5 Grendel ammo brings a weight increase of about 2.4 pounds over 5.56. If you want to carry the same weight in 6.5G as you currently have in 5.56, you reduce the basic load from 210 rounds to 147. Please realize that there’s no “magical” number of rounds in the basic load, these things are up for debate. We won World War II, for example, with a basic load of 80 rounds of .30-06!
How to deal with the weight issue? One of my answers is that it’s already an unspoken doctrine that you “double-tap” with 5.56. If one round of M855 5.56 weighs 186 grains, and one of 6.5G 123gr weighs 265 grains, then using two 5.56s for one 6.5G actually uses 140% more ammo weight! So I would argue that the increase in effectiveness of the individual round offsets some of the weight increase. Having said that, experienced combat troops take as much ammo as they can carry, anyway, and a former Marine who fought in the early Hill Country battles in Vietnam swears to me that being able to carry a lot of rounds of 5.56 kept him and his buddies from being overrun. So a realistic basic load is a serious issue.
Having acknowledged that reduced ammo weight is a worthy goal, we must realize that this, too, is an arbitrary figure, open to debate. For example, if you carry an ammo weight-saving initiative to the extreme, we’d all be armed with .22 LR! Obviously, a compromise needs to be made between cartridge weight and projectile effectiveness. The debate between the weight of 5.56 and 6.5G simply rests in where you decide to draw the line. I find the “optimum compromise” in an intermediate position between 5.56 and 7.62, and I think the combination of post-WW2 studies and recent, real-world experience with 5.56 deficiencies supports this. So I suggest we find ways to shave 2.4 pounds in other gear to allow an intermediate-cartridge basic load that brings with it no weight penalty.
But where a shorter-range intermediate cartridge would simply add weight to the overall burden but only give limited additional capabilities, it’s different with the 6.5G. Because the longer-range 6.5G also replaces the range and penetration of 7.62 NATO M80, it allows you to offset some of the earlier weight increase by greatly decreasing the weight for an M240 machine gun team, as I’ve detailed elsewhere. For the same weight of 2,000 rounds of 7.62, you can carry 2,924 rounds of 6.5G, or you can have 2,000 of 6.5G and save 35 lbs on ammo alone (not including a lighter MG weight).
The two things that would make my arguments invalid would be if the 6.5 Grendel had worse terminal performance than 5.56 and worse range and penetration than 7.62. These things need to be rigorously and scientifically tested; some have already taken place, and more are to come.
What seems clear to me at this point is that there is no technical reason the 6.5 Grendel couldn’t serve our military as a general-purpose replacement for both 5.56 and 7.62; it’s a matter of political will. I would like to see some innovative soul study the logistical and financial efficiencies we’d gain from having only one set of general-purpose weapons and one cartridge, instead of our current system cobbled together that dictates a 5.56 version and also a 7.62 version of basically the same weapon.
H&K 91 A2 is tops IMHO.
[1] How could the author of the article failed to mention the Stg 44, the granddaddy of ALL assault rifles [7.9 cal, I believe] in the article? Nor does he mention the German Army’s study of infantry combat that led to it’s development.
[2] The Army’s Spec Ops guys have gotten Remington to develop a 6.8 round they’d like to see in use on an M4 platform. So you’re pretty close to getting what you’d like, caliberwise when it gets adopted
The complaints allowed as valid here are the complaints I heard when I was in Vietnam. The other complaints the author cites I have not heard before. The answer was then the AK-47 which some troops traded for. It is not good when your weapon jams repeatedly because of the extremely dirty environment of the engagement. The M16 improved considerably over the course of that war but didn’t get better at stopping a charging enemy soldier. I agree on the unsuitability of the old Garand for jungle or city fighting but the solution has been apparent for a long time and that is the 7.62x39 round or something very like it. Better would be a version of that round that is not interoperable with the weapon most likely in the hands of enemy fighters. I know very little of the arcana of different ammo and different devices but those have been my observations. I have had both a 7.63x39 weapon and an AR. The .223 is just too easily deflected in foliage and that critter you shot can move too far before it knows it is dead.
The 5.56 with the M4 platform is a great manstopper. It’s important however to use soft point projectiles. Here’s an example:http://www.btfh.net/shoot/misc/bp-wastes-tonk.wmv
Disadvantages:
* Many of the points already mentioned, power and reliability under extreme use.
* I think the darn thing could use an operating knob or handle on the bolt carrier. The net weight gain would be zero, since you could then eliminate the forward assist.
{Not my original idea, I saw one years ago with this custom modification. But honestly, it looked a little too delicate for rough use.}
How many 6.5G’s fit into an M-16 magazine, compared to 25 6.8SPC’s?
Tracer burnout distance for the 6.5? Oh, the tank crews are just going to LOVE this swell idea. the whole point of having a co-ax gun is that up close the gunner can burn off a short burst from the coax, and when he sees tracers bouncing every which way, knows he's on a hard-skinned target deserving of the main gun round up the spout. Any bets on for how much of a distance the 5.56/6.5mm trajectory and that of the 120mm coincide?
Some tank commanders use their .50 similarly, but usually have only a 200-round can of ammo available; more often it's fed straight out of a 105-round M2A1 .50 cal shipping can, with only 10 cans normally carried. the standard load of 12,400 rounds of linked 7.62mm for the co-ax and the loader's roof gun is a little better. And, BTW, we need to consider performance in Arctic conditions as well....
I’ll always prefer the M14 or the FAL any time, anywhere.
Some have indeed taken place: .256/.276 Enfield cartridge, circa 1910
Recognising that the .303 cartridge as well as the Lee-Enfield bolt-action rifles were becoming obsolescent, during World War II the British Government set up the Ideal Cartridge Panel to decide on a new cartridge for the British Army, taking account of past experience and information coming in from the battlefield. The panel was headed by Richard Beeching, Deputy Chief Engineer of the Armament Design Establishment of the Ministry of Supply, the body concerned with the design and production of weapons and ammunition. The panel was composed of engineers, designers and soldiers, many of whom would play a role in the design and thinking behind the EM-2.
British 1945 "Ideal Cartridge Panel" conclusion and result:
Perhaps the most interesting and instructive series of experiments took place in the UK in the late 1960s, when thorough attempt was made to design an ideal military small-arms round. This started with calculations of the bullet energy required to inflict a disabling wound on soldiers with various levels of protection. The energy varied depending on the calibre, as a larger calibre required more energy to push it through armour. For example, it was calculated that while a 7.62mm bullet would need 700 joules to penetrate modern helmets and heavy body armour, a 7mm would require 650j, a 6.25mm 580j, a 5.5mm 500j and a 4.5mm 320j (this last figure looks wrong and should probably be 420j). This figures applied at the target; muzzle energies would clearly have to much higher, depending on the required range and the ballistic characteristics of the bullet.
A range of "optimum solutions" for ballistics at different calibres was produced. These resulted in muzzle energies ranging from 825 joules in 4.5mm to 2,470j in 7mm. More work led to a preferred solution; a 6.25mm calibre with a bullet of 6.48g at 817 m/s, for a muzzle energy of 2,160 joules. The old 7mm EM2 case was necked down to 6.25mm for live firing experiments, although had the calibre been adopted a new cartridge would probably have been designed. Tests revealed that the 6.25 cartridge matched the 7.62 NATO in penetration out to 600m and remained effective for a considerably longer distance, while producing recoil closer to the 5.56mm. 
bump for later.
Army SOCOM already proved that the H&K 416 in 6.8 SPC is a superior combo for the type of warfare we face today. The army brass got wind of this verification and in a desperate attempt to CYA they recalled the SOCOM weapon orders on the grounds of logistics or some malarkey.
I disagree with the handgun choices, the caliber is right on with the 45(when will we ever learn?). The 6.8 SPC is probably the cartridge of the future, simply because it fits into the current AR platform with few modifications.
Small caliber hypervelocity rounds such as the FN5.7are entirely unsuitable for sidearms. They have excellent performance against armor, but against unarmored individuals they have extremely poor wounding and stopping performace (they are suitable for SMG's however, as a large number of small wounds from a controllable full auto weapon is a decent wounding mechanism if youn dont mind expending lots of ammo).
This sidearm should be DA/SA, with a three position safety (Safe, Fire, Decock) allowing for all modes of operation. Some say they would prefer a DAO (or safe action such as in Kahr and Glock pistols) with no safety, however I prefer the flexibility and operating feel of traditional DA/SA pistols.
I believe this weapon should be a "compact" pistol, which conventionally means a 4-4.5" barrel; and a slightly smaller grip circumference and frame height than a "full size" pistol or current service pistol, with a capacity of 8-12 rounds. This will make it more flexible for carry, and less intrusive in most missions. Importantly this will also make it more confortable for those with smaller hands (a major problem with the M9), while only giving up a few rounds of capacity. This pistol should have highly visible, snag free, low profile sights with tritium inserts.
I acquired the S&W M&P in .45 recently. It's a joy to shoot with less percieved recoil than the 1911, better reliability and included optional grip palmswells to accomadate shooters with smaller and larger hands.
Unlike the other M&Ps it does have a externally activated safety lever (supposedly in anticpation of DOD contracts.)
I've probably ran over a 1000 rounds through mine since March without any stoppages. It's been cleaned about 3 times.
I’m a big fan of the 6.5mm and after Archy’s (as usual) highly informative post, I’m now interested in the 6.25mm as well.
All of the talk about the 6.5mm Grendel or the 6.8 SPC replacing the 5.56 is a very bad idea. Both the 6.5 Grendel and the 6.8 SPC are compromises limited to the overall cartridge length defined by the M-16 magazine. The Pentagon needs to get past that thinking and adopt the best cartridge first, and then build the magazines and rifle around it.
While I like the 6.5 Grendal’s performance, I’m thinking more along the lines of the 6.5X47 Lapua because it looks like it will feed more reliably in a full auto. Whatever caliber is eventually chosen, it should not be a compromise designed to fit in the magazines of a 40 year old rifle design.
The next rifle and military caliber adopted should be the best our military, our countries engineers, and yes our countries highly experienced competetive shooting community can come up with. Our soldiers, sailors, marines, and airmen deserve no less than the best.
Not me. But I despise the crappy 30-round magazine design. Wear or mediocre manufacture makes it even worse.
Bushmaster A3 Commando - I really like this configuration
thanks, bfl