The Definitive Military Service Calibre and Rifle For the 21st Century

Hi, my name is Mike Staples and I am an ex Australian Army Fitter Armament or to put it more simply, an Armourer. My experience takes in all Australian Military Weapons including pistols, rifles, SMGs, LMGs, HMGs, Mortars, recoilless rifle, and artillery pieces, as well as mounted guns in our Armoured vehicles that were current at the time of my service. On top of that experience is my love of shooting, which started when I was around 6 years of age and has continued to this day, some 51 years later. I have been asked by Mr. Hawks to write an article on a suitable calibre for a General Purpose Military Rifle (GPMR), and whilst the calibre is important the delivery system, a.k.a. the rifle, is equally so. That being the case, this first article will establish what I feel is a suitable calibre to replace the 5.56mm NATO round, whilst the second part will put forward suggestions on a suitable rifle.

There has been a multitude of cartridges that have been used by the worlds Military Forces, and to compare all of them in the pursuit of the "perfect calibre" for the 21st Century would take many pages and many hours of research. Therefore, I will concentrate on those which have been used by the US, Australia, Great Britain, and NATO Forces in recent history.

Since the Vietnam War there has been a move to make one calibre "the NATO calibre," and at this point in time that calibre is the 5.56mm NATO. The main reason for this, from my perspective, is to make all aligned forces users of this calibre. NATO is a collage of many countries. When NATO forces either take up arms against an aggressor or have become an occupation force on behalf of the United Nations inside a country that has experienced a war or uprising, many soldiers from different countries make up that force. If all used a different calibre in their GPMR, ammunition re-supply would be a nightmare.

The answer to this question will not be easy to establish, as every country and every soldier has a differing opinion. While some like one calibre and one style of rifle, others have trouble accepting those choices. They may prefer to stay with whatever their country uses, as it has become familiar, comfortable and a trusted friend.

I am told by Mr. Hawks and some of my Australian Army friends that there are moves afoot to abandon the 5.56mm calibre. (These may, of course, come to nothing--particularly as they originated with the troops, not the high command. -Ed.) Apparently the U.S. Senate is currently considering a new calibre (the 6.8mm SPC) for use by Special Forces. As the actions of the U.S. military have in the past greatly influenced the NATO countries, it is quite likely that whatever is chosen by the U.S. will eventually become the NATO standard.

Before they do, I would like to bring to the attention of the leaders of the NATO countries a calibre which is not only a suitable upgrade, but that eclipses the two best service rounds yet devised.

To do this I must compare the two standard NATO rounds used today (7.62x51mm and the 5.56mm) with what I consider to be the best choice. I will include in these comparisons the .30-06, a world record holder for all ranges prior to the advent of the .308 Winchester (7.62x51 NATO) and which was, over a number of decades, the U.S. calibre of choice.

The .30-06 was brought out in 1906 to replace the original cartridge for the Springfield rifle of 1903, which initially was chambered for the .30-03 round. Both cartridges fired a .30 calibre bullet, but the '03 had a 220 grain monster and a very long neck to accommodate it. The neck of the '06 case was shortened by .07 of an inch and became the standard military cartridge with a 150 grain spitzer projectile. The '03 and '06 signify the year of first use.

This round was used in every .30 calibre weapon in the US armoury up until the late 1950s. These included the M1 Garand, the BAR and their main LMG, the .30 calibre machine gun. At that time the .30-06 was replaced by the ballistically identical but 10% smaller .308 Winchester (7.62mm NATO) cartridge.

Why they ever abandoned these powerful cartridges, exchanging them for the .223 (5.56mm) "squib" used in the M16 Armalite rifle, is anybody's guess. (The official reasons included reducing recoil and facilitating fully automatic fire. -Ed.) That change, as far as I am concerned, did the US soldier a great disservice. More on that in the second part of this article.

Detailed tables will establish my calibre of choice and the reasons for it. The calibres I will compare in this article are as follows:

(3) 5.56mm (.223 Rem.) - .22 calibre, .224" projectile (military calibre) (4) .270 Winchester - .270 calibre, .277" projectile (civilian calibre)

Before I proceed, I would like to clarify "calibre" and the fact that some projectiles appear to be the same size as the calibre.

Calibre is described as being "bore" diameter (inside bore diameter, ID), which is gauged across the lands of the rifling in the bore of a weapon. The diameter of the projectile is usually equal to the "groove" diameter of the bore, measured across the depth of the groves in the bore (outside bore diameter, OD), or in some cases is slightly bigger than the OD of the bore.

This difference, if the projectile is slightly bigger than the distance across the grooves, is possibly only 1 or 2/1000ths of an inch. This is ordinarily only the case when the projectiles are made from a lead-antimony mixture, as these projectiles are soft enough to deform sufficiently to allow the projectile to fit the barrel. I would suggest that all copper clad (jacketed) projectiles would be the same size as the OD of the bore. To be effective, all projectiles must, at the time of firing, "take" the rifling of the weapon, making a gas tight seal.

Some common examples of this differentiation in calibre are the .308 Winchester and the .243 Winchester. The .308 Winchester is in reality a standard .30 calibre cartridge. .308 rifles have a bore diameter of .300" and a groove/bullet diameter of .308". (Both dimensions are identical to the earlier .30-06 and .300 Magnum.)

The .243 Winchester is a similar case and rifles in this caliber have a groove/bullet diameter of .243". Both the .243 and .308 were named for their groove diameter rather than the more traditional bore diameter. This method of nomenclature became popular after the 1950's and many, but not all, cartridges developed since that time have been named for their groove/bullet diameter.

To arrive at a suitable calibre for a GPMR one must take into consideration the following minimum criteria:

(1) Does the selected calibre have minimal bullet drop at ranges out to a minimum of 400 yards (366 metres)?

(3) Is the projectile heavy enough to deliver sufficient knock down power (Kinetic Energy) at all ranges out to 400 yards?

(4) Will the trajectory of the projectile be relatively flat when compared with other suitable ammunition?

(5) Is a complete round (i.e. cartridge case + projectile + powder + primer) light enough to allow a soldier to carry a minimum of 300 rounds on his person?

(6) Will the selected calibre and projectile be accurate enough to shoot groups of 5 inches/125mm or less at the stipulated minimum range? (The rifle being used will be a factor here.)

(7) Will the selected calibre and projectile be able to attain velocities of at least 3000 FPS from a self loading service rifle?

The following tables clearly demonstrate what round I feel conforms to the above criteria. The comparison rounds are:

(2) The 7.62 x 51 round, using 168 grain projectile with a MV of 2700 FPS (I do not have detailed tables for a MV of 2650 FPS, so I have used a slightly higher MV to highlight the differences).

(4) A .270 (6.858mm) round using a new case with the same dimensions as the 7.62 x 51 case, except it is necked down to accept a .277" diameter projectile. (A similar situation to the .243, which uses a necked down .308 case). In European (or modern military) nomenclature this would be a 6.85 x 51mm cartridge. 150 grain bullet at a MV of 3000 FPS.

Note: All projectiles are spitzers (pointed) with boat tail base, as I have no tables for FMJ projectiles. All tables, are based on information, as found in the Sierra Reloading Manual, 2nd edition; Sighting plane is assumed to be 1.5 inches above the axis of the bore; All distances are in YARDS. 1 Imperial Yard = (approx.) 0.9143 metres.

As the above tables clearly demonstrate, the 5.56mm NATO round is as suggested a "squib" and has precious little remaining energy beyond 200 yards compared with the other calibres, and I feel that this is a generous assessment. Its bullet drop characteristics are better than the projectiles of the 7.62 and .30-06, and it shoots flatter than both. But, lacking their knock-out punch, so what?

On the matter of accuracy with the 5.56 NATO round, I would dispel a myth that was rife in Vietnam. That being the projectile "tumbled" or rotated in an ellipse fashion along its axis. This assumption was made by many soldiers because of the damage the projectile could inflict at short range.

The reality is that any sharply pointed FMJ bullet may tumble if it hits something hard enough to destabilize or deform it, a large bone, for example. This tumbling effect has been noted by US troops ever since the adoption of the .30-06 cartridge and its 150 grain spitzer bullet in 1906. It is not unique to the 5.56mm bullet. But often a FMJ bullet will simply drill a bullet diameter hole straight through the target, particularly in soft tissue. The terminal performance of any FMJ spitzer bullet is unpredictable and any result other than a caliber diameter hole cannot be relied on.

Both the .30-06 round and the 7.62 x 51 round perform very well at all ranges out to 500 metres, with sufficient energy to stop most men in their tracks. I read some years ago that a rouge African Elephant was shot and killed at a range of approximately 100 metres with an FMJ 7.62mm NATO round. Before WW II many elephants and other heavy game were killed at fairly close range by .30-06, .303 British, and 8mm Mauser FMJ bullets.

Both the .30-06 and 7.62x51 are very accurate rounds, especially in bolt action or single shot rifles, as their target shooting records attest. There is also the indisputable fact that US snipers in Vietnam (and other theatres since) used the 7.62x51 round very effectively at long range.

I am reliably informed that, whilst the round was a 7.62x51, its similarity to that used in the GPMG M60 and the Australian L1A1 SLR ended there. Each sniper was responsible for handloading their own ammunition and, as their rifles were bolt action repeaters, it's quite possible that different projectiles and powders were used.

One shot kills have been recorded out to ranges of 1200 metres, and that is no mean feat.

I have personally experimented with my Omark single shot, heavy barrel target rifle, which has a Weaver 8 power scope fitted. Using 150 grain Sierra MatchKing HPBTs, IMR-4064 powder and magnum primers I have chronographed projectiles 15 feet from the muzzle at speeds averaging 2900 FPS. I have, on numerous occasions using that rifle and my hand loaded rounds, shot 6 inch groups or better at 800 metres.

If the Australian military and the US Senate are investigating the possible change to a bigger round for their GPMR and section LMGs, then the .30-06 and the 7.62 x 51 rounds should be high on their list.

I would ponder the question, "if they are considering an upgrade of calibre, is that an admission that the 5.56mm round does not stack up against the previously used 7.62x51 NATO round?"

By using the .30-06 and the 7.62x51 cartridges as a bench mark, I have looked for a suitable round that can deliver everything required of a GPMR. The round and calibre are only part of this equation. However, I would point out that once a suitable calibre has been identified a competent rifle can be built around it.

A nearly ideal calibre is the .270 Winchester, which has been around since 1925. The civilian round uses a necked down .30-06 case and has proven to be an excellent hunting calibre. The only problem with this round is its overall length, which can create feed problems in semi-auto and automatic rifles. That being the case, it could cause stoppage problems that can endanger a soldier's life. However, this can be overcome quite simply by the introduction of a new .270 cartridge using the 7.62x51 (.308 Winchester) case.

The .243 Winchester and 7mm-08 Remington cartridges use a necked down .308 case and there is no reason why a new case cannot be made to suit the .277" diameter projectile of the .270. It could be called the .270 Military/NATO or the 6.85x51mm Military/NATO. Its slightly shorter length would overcome feed problems and its overall total weight would make it possible for a soldier to carry upwards of 300 rounds on his person.

The above tables clearly demonstrate that the .270 Winchester calibre outshines the other comparison rounds in all respects and with a slightly lighter (130 grain) projectile in a good rifle, MVs up to 3000 FPS should be achievable.

It is my opinion as an Armourer that kinetic energy and accuracy, at all ranges out to at least 400 yards, should be the base criteria for a calibre suitable for a GPMR. Every time a soldier faces an enemy his target can and does shoot back. Therefore, he must be given every advantage to negate this threat before he or a fellow soldier is killed or wounded.

The figures supplied by Sierra are fairly complex and their calculations are not much better, but the everyday soldier only needs to know the following:

(3) The holdover height at ranges beyond zero range, should it be necessary to shoot beyond that range.

(4) He must have an understanding of what kinetic energy is and why it is important to himself as a soldier and the man standing next to him.

(5) Finally he must learn how to estimate distances accurately, unless he has the use of modern range finders or estimators.

In the next article I will marry this round with a tried and proven rifle, which I believe will give our soldiers a decided tactical advantage. It is very necessary for our soldiers to be confident that one round will incapacitate his enemy, without having to throw an entire magazine at him.

I came across some info you might be interested in about the new round the military is contemplating.

"6.8 mm rifles weigh the same as their 5.56 mm counterparts. 28 rounds of 6.8 mm fit in magazines the same size as 30 rd 5.56 mm mags. Ammunition weights are obviously different, as the following comparison illustrates: 30 rounds of 5.56 mm M855 weigh about 0.8 lbs, while both 28 rounds of 6.8 mm and 20 rounds of 7.62 mm M80 weigh roughly 1 lbs. Personally, I would gladly give up 2 rounds and 0.2 lbs per magazine compared to 5.56 mm for the significantly superior terminal performance of the 6.8 mm.

"The folks who conceived, designed, and tested this system are HARD shooters, VERY experienced in special warfare combat, as well as world-class match shooting. They wanted something more effective in combat than the 5.56 mm they had been using for years. They looked at all the options, tested them, and chose what worked best. End result--the 6.8 mm is significantly more effective for combat applications than any 5.56 mm. This is a FACT, not speculation."

"The 6.8 x 43 mm SPC is what it is because this configuration offered the BEST PERFORMANCE FOR THE INTENDED MISSION: CQB to medium range engagements, using an M4 size weapon and allowing use of existing components, such as receivers, web gear, and SOPMOD accessories. The caliber is 6.8 mm, because that demonstrated the best combination of accuracy, reliability, intermediate barrier penetration, and terminal performance compared to SPC variants tested using other caliber bullets, such as 6 mm, 6.5 mm, 7 mm, and 7.62 mm. The 6.8 mm SPC uses a 43 mm case because that worked better than other case lengths, including 45 mm. The landwarfare legal 115 gr OTM bullets offered the optimal performance for the intended military combat role compared to the other 90 to 140 gr bullets that were tested (Note--for other uses such as LE or hunting, 6.8 mm polymer tip and bonded JSP bullets offer outstanding performance). The 6.8 mm does not work with existing bolts, because testing proved that that option was not as reliable. Likewise, the SPC is not based on a PPC cartridge, because that route, while very accurate for target shooting, did not prove as effective for COMBAT applications."

anyone interested in further information on this might like to go to: http://www.tacticalforums.com/cgi-bin/tacticalubb/ultimatebb.cgi?ubb=get_topic;f=78;t=000512

some of the gentlemen involved in that discussion appear to be very knowledgeable.

I'm a gun smith and a retired Ranger combat vet.
The rumors I'm hearing is that there are some specialty weapons just around the bend. I don't think these are going to be standard issue, but weapons built for clearing buildings in an urban setting.
I think you are going to find a 32 caliber round based on the old 32/30/35 rimless Remington case. Most automatic actions don't do well with a rimmed case. I hear they are going to shorten the old Remington case and put more impact energy into a shorter round and a shorter rifle.
For a main battle rifle I have no problem with the 7MM08. It has good energy, great accuracy, and I think it will be easily accepted by the troops.
I'm also a 280 Rem fan, but I like it better as a 280AI version.
The 308 round is a good round as is the 30-06, but there are more efficient cartridges available. The .223/5.56 needs to go.

A Cartridge of Superior Caliber

With regard to the selection of a new cartridge for use by the US Armed Forces, one issue often not addressed is the current capacity (or lack there of) to manufacture small arms ammunition. Currently several nations are involved in the manufacture of ammunition as the US lacks the capacity to manufacture sufficient small arms ammunition for it’s own use, even for the current low intensity conflict. Adoption of any “new as yet to be proven cartridge” would only increase the difficulties faced by US Forces in the foreseeable future.

It appears that a majority of people at all levels agree the 556 or 223cal used by the current M16 is a poor performing cartridge especially since the use of optical sights has enhanced the accuracy of US Forces and the nature of current conflicts require a more rapidly disabling, longer legged overall more effective round than the current 223. The 308cal or 762 NATO is really the best choice for many reasons. The 762 is already in US and (less importantly) NATO inventories. The expanded use of the 762/308 would allow our soldiers to use one cartridge for all small arms. In Tanks (The Coaxial Machine Gun is a 762 usually the MG240), Many of our Helicopters use the M60 in 762 for door gunners. Vehicles like the Humvee unless equipped with the M2, or M85 (50 cal) use the M60 in 762. The M60 has served as a squad weapon since Vietnam and the "Pig" at the party is proven and does an excellent job. To have one ammunition caliber (762/308) (besides pistol) from the Squad Level up would create a tremendous logistical advantage. Units running low on ammunition could use 762 linked ammo simply by breaking it down and loading it into their 308/762 M16s. Tank Crews whom routinely carry 10s of thousands of 762/308 ammunition along with others could easily distribute linked 762 ammunition to units pressed or running low. The same is true for all tracked and wheeled vehicles in US inventory. Simply by changing some of the dimensions of the M16 the 762/308 round is easily accommodated. Further the 762/308 M16 has already had years of refinement and proofing in the AR10 or Armilite version. This version has been produced for the General Citizenry of the United States for many, many years. Their will be little transition time required for US Forces as functioning/assembly and disassembly of a 308 M16 is virtually identical to the M16. The 308/762 M16 will also be more reliable due to the larger dimensions of the cartridge allowing for greater overall tolerances than with the current smaller 556 or 223 round. The 308 or 762 round in match grade (most precisely metered powder charge and bullet weight/dimensions) is our most common sniper round being employed in Match Grade M14 (M21) and Custom 700 Remington Sniper Rifles world wide.

There has been much made of the ineffectiveness of the 223 round. When organized armies faced each other, causing casualties but not killing ones enemy was preferable. Casualty care requires great logistical efforts, failure to care often results in a reluctance to fight and reduced effectiveness. The oft quoted requirement of 10 men to care for one wounded does not apply to stateless terrorists. Their people are not likely to be on the battlefield attending their wounded along with the required logistical issues. US Forces or our allies wind up caring for our stateless enemies. Killing them is far preferable to wounding in nearly all circumstances for many reasons not the least of which is the apparent tendency even when treated humanely to return to the conflict attempting again to Kill Americans or our Allies at the next opportunity. The 308 is a proven killer easily lethal at 1000 meters. In close quarter battle (CQB) the 308 rapidly incapacitates. The 308 can be produced in sufficient numbers to maintain our stocks. The 308 is consistent with our current inventories. The 308 allows 10s of thousands of existing weapons in US inventory to remain viable in fact adopting the 308 enhances their effectiveness and the overall effectiveness of US Small Arms and Units. The 308 has proven lethality and range, is not reinventing the wheel and has many advantages as discussed here.

W.

You are correct on the case it is going to be based on. It appears that the caliber will be the 6.8 which is right around .270. The Round is known as the 6.8spc. They experimented with calibers between 6.5 and 7.62 before concluding that the 6.8 would best meet all of the requirements.

From what I understand the requirements were:
CQB to medium range engagements (out 400 meters).
Use an M4 size weapon
Use existing components, such as receivers, web gear, and SOPMOD accessories.
Accurate,
Reliable
Intermediate barrier penetration,
Terminal performance better than that of 5.56

These requirements were put in place by the Spec Ops community, who also did the lions share of development.

I understand that they are also working on a new general issue round which will be in the 7mm, .280 size range with flight characteristics and terminal ballistics similar to the 7.62x51.

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