Caliber Configuration: How It Got to Where It’s At, and Where It’s Headed

This post was written as a companion to an upcoming Gun Guy Radio podcast, hosted by Ryan Michad. The discussion below will be expanded upon in the show when it’s released later this month, but for now, read on to learn more about the past, present, and future of infantry weapon calibers!


1: What is caliber configuration?

Caliber configuration is a term used to describe the nature of small arms ammunition, the topic of this post dealing specifically with ammunition for infantry weapons. First, a definition is in order: Caliber configuration refers to the specific dimensional and ballistic characteristics of a cartridge, in the case of this post a military standard infantry weapon cartridge. 5.56x45mm NATO has a different configuration than 7.62x51mm NATO, which in turn has a different configuration than 9x19mm NATO. Each of these rounds serves their own purpose, although for the purposes of this article we will ignore pistol caliber configuration.

It is complex subject, with few easy answers, and is often erroneously reduced to a matter of ballistic “performance” without regard for actual real-world effectiveness and balance. The demands place on the infantry caliber pull in opposite directions: The ideal round kills instantly with one shot, has no recoil, weighs nothing, has a perfect laser-trajectory, no muzzle flash, costs nothing, takes up little or no space, creates a suppressing hurricane of air and loud sonic boom around the target, yet is silent at the muzzle, penetrates all barriers at all ranges with no loss of effectiveness (while still having limited penetration for use in training facilities), and has no maximum range (while still having a maximum range within normal Army training ranges). Obviously, many of these “ideal qualities” are in perfect opposition to one or more of the others, and in many cases it’s a challenge to even study a single performance metric well enough to characterize in such a way that its importance can be qualified enough to set a requirement. This is, for example, the case with suppression. Enemy forces clearly are suppressed by close small arms fire, but studies on which calibers suppress the best, and how to optimize a projectile to suppress the enemy have been mostly inconclusive. Therefore, there is a serious question about how suppression should be valued when designing a new infantry caliber, one that’s difficult, if not impossible, to answer currently.

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Shown is the 8×63 Bofors on the left, and the 5.7x28mm on the right. Attributes of both rounds are desirable in infantry small arms rounds, but their great differences are obvious. Therefore, a balance must be struck.


2. A very brief history of military calibers

Beginning with the metallic cartridge revolution in the 1850s, military forces began adopting metallic cartridge-firing guns in the late 19th Century. While the benefits of the breechloading single-shot weapons that fired them were obvious, the metallic cartridges themselves brought both advantages and disadvantages. The metal shell holding the propellant and primer was much more resistant to the environment than previous paper cartridges, yet also added weight and bulk to the infantryman’s ammunition. While the first metallic cartridges were designed around the previous muzzleloading caliber paradigms, improvements were quickly made, chiefly by reducing the caliber. .58 caliber bullets gave way to .50 caliber, then .45, and eventually jacketed .30 caliber round-nosed bullets. Interestingly, these last projectiles, tough enough to withstand the violence of accelerating to muzzle velocities above 1,900 ft/s, severely compromised the shock effect of the rounds, although they greatly augmented the penetration. To counteract this problem, different exposed-lead bullets were invented, both field-expedient and production; the most lasting of these being the jacketed hollow point and jacketed soft point types, still in use in the civilian world today. These designs, however, were quickly deemed needlessly cruel in international law, and banned in warfare by the 1898 Hague Convention. From the turn of the 20th Century, the early ballistics science of the period made possible bullets shaped for supersonic flight. These bullets possessed higher muzzle velocities than ever before, with the often-copied Spitzgeschoss Patrone nearing 2,900 ft/s. These bullets complied with the provisions of the Hague, but due to their shape and high muzzle velocity performed very differently in tissue. Their rear-heavy conical shapes quickly destabilized, and their high energy and high muzzle velocity greatly improved effectiveness versus their round-nosed predecessors.

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The 7.65x53mm Argentine on the left is typical of ~.30 caliber rounds from before 1905, with its round nosed bullet. On the right is a 7.92x57mm Turkish round, loaded with an S Patrone type spitzer projectile, which became the pattern for military rifle rounds after 1905.


This improved effectiveness has caused controversy to this day regarding the legality of certain types of bullets, discussed in more detail in this article. The high muzzle velocity, lighter weight, and better aerodynamics of the new “spitzer” bullets versus their round-nosed predecessors, coupled with requirements for new bullet types such as tracer, anti-balloon, and armor-piercing, halted temporarily the drive for smaller calibers. Many and services had up to this point adopted calibers as small as 6mm, and experimented with ones as small as 5mm, but for the next 50 years (from 1904 with the adoption by Portugal of the 6.5×58 Vergueiro to 1954 with the adoption by Venezuela of the short-lived 7x49mm Liviano) no new chamberings smaller than 0.298″ would be adopted as standard by a major military force. In fact, several countries, including the Japanese, French*, and Italians, would switch from smaller chamberings to larger .30 caliber rounds during this period.

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The 6.5x54mm Mannlicher-Schoenauer on the left was adopted by the Greek Army in 1903, and was one of the last calibers below 0.298″ bullet diameter adopted by a major power for fifty years. On the right is the 7x51mm FN/Liviano, adopted in 1954 by Venezuela for their FN FALs.


Since the introduction of the metallic cartridge, chamberings intermediate in power between a standard rifle cartridge and pistol ammunition were used in special roles to augment the firepower of special infantry units. These rounds weighed and recoiled far less, while delivering more range and effectiveness than standard pistol rounds, making them highly suitable for use in rapid firing weapons. However, until the mid-1940s, these weapons were considered specialist items, unable to meet all the requirements (particularly the long-range capability desired in machine guns) necessary for a standard issue round. During World War II, however, the value of individual automatic weapons in the form of expedient-to-produce pistol-caliber submachine guns proved that organic automatic firepower was a requirement for the infantry in the second half of the 20th Century. For the Soviet Union, after their experience fighting against Germany during World War II, this meant the adoption of the intermediate 7.62×39 caliber as the standard round of the squad, but the Western powers would take a more conservative path.

This apex of the full-power cartridge came with the de-facto standardization of the American .30 Light Rifle cartridge within NATO in 1953, leading to the familiar 7.62x51mm NATO caliber. This round was essentially a shortened “economy” version of the traditional .30 caliber round that had dominated small arms developed for the past half-century, having been developed explicitly by the United States to save brass and allow a shorter length action for automatic weapons. Thanks to the US preference (and NATO’s inability to say “no” to their key member) for a universal full-power round, it defeated its British intermediate .280 caliber competitor, leaving the UK with somewhat bruised national pride. However, not even the US could ignore the value of the intermediate round for long.

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Left: The 1.95″ long case FA T1E1 round, a prototype for what would become 7.62x51mm NATO. Middle: The .280/30 British, with a 140gr steel-cored pink-tipped Type C bullet. Right: 7.62×39 FMJ.


*In the case of the French, they had adopted – but not successfully standardized – the 7mm Meunier (one of several unsuccessful “military magnums” of the brief period between 1905 and the end of WWI), only to abandon it after 1918 and adopt in the 1920s the .30 caliber 7.5x54mm.


3. Small Caliber, High Velocity

This brings us to the modern paradigm, called “small caliber, high velocity” (SCHV) in literature. This was essentially a rebirth of the concepts trialed in the late 19th Century – whereby a smaller, lighter projectile driven at higher velocities would give a flat trajectory, good penetration, light overall weight, and low recoil – but coupled to a new context. While the small caliber high velocity rounds of the 19th Century focused on achieving ever longer effective range, the new SCHV of the latter half of the 20th would focus on giving the lightest possible weight, lowest possible recoil, and the highest possible effectiveness out to medium ranges. The standard bearer for this concept was the US 5.56x45mm round, still in use in modified form today. Development of the SCHV concept began in that country in the early 1950s, based on research conducted in the late 1920s and during World War II and Korea. Experiments began with modified M2 Carbines chambered for .22 caliber centerfire rounds, and subsequently evolved into a standard infantry rifle ammunition concept that would halve the weight of ammunition carried by the infantryman while retaining most of the effectiveness out to short ranges. This, coupled with a lightweight automatic weapon in the form of the AR-15, proved to be a much more modern and overall effective combination than the previous full-power 7.62 NATO caliber infantry rifles. In 1963, the United States Army adopted the AR-15 as the “XM16E1” and the 5.56mm round as “M193”, in theory as a temporary solution until development of the extremely advanced even higher velocity flechette-firing Special Purpose Individual Weapon could be completed. It never was, and in 1970, after infamous teething troubles with the ammunition and rifle barrels in the Vietnam War, the “stopgap” M16 was made standard issue by the United States, replacing the M14 as the primary arm for US GIs.

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US Army caliber concepts of the 1950s and 1960s. Left: The .22 Aberdeen Proving Ground Carbine, designed for the M2 Carbine and the precursor to all modern SCHV rounds. Middle left: 5.56mm M193. Middle right: 7.62x51mm M198 Duplex. Right: XM216 flechette, from the SPIW program.


The AR-15 and its lightweight ammunition sent shockwaves through the world of infantry small arms, in both the West and the East. With the US adoption of an intermediate round just a decade after they pushed the full-power 7.62mm round onto NATO, the Organization turned to yet another competition to determine a second standard round, before domestic intermediate caliber developments could ruin the NATO standardization agreements. The competition featured entrants from the USA, France, Belgium, Germany, and the UK, but the winner was the SS109, a Belgian loading of the 5.56x45mm, which became the basis for NATO-standard 5.56mm ammunition, including M855.

In the Soviet Union, work had begun as early as 1959 on an SCHV round that could match or beat the American 5.56mm M193. The story is told in more detail here, but the round that resulted in 1967 was the 5.45x39mm, standardized with the 7N6 loading in 1974.

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Modern SCHV rounds. Left: Danish 5.56mm SS109. Middle: Korean 5.56mm M855. Right: Soviet 5.45mm 7n6.


China, paralyzed by Mao Zedong’s rigid economic policy, remained mostly dormant in the field of small arms until the restructuring undertaken by his successor, Deng Xiaoping, who took office in 1981. Several Chinese military programs gained momentum in the subsequent years, including a program for a modern general purpose SCHV cartridge, which became the twin 5.8x42mm DBP-87 and DBP-88 rounds. These replaced the 7.62×39 and to a more limited extent the 7.62x54R cartridges in Chinese service, but in having two distinct loadings with different overall lengths fell short of being a truly unified solution, and so in the early 2000s development of a single round that could replace both 5.8mm loads began, finalized in 2010 as the DBP-10.

This “triumvirate” of SCHV rounds represents the current state of the art of infantry small arms ammunition today, supplemented by the older full-power cartridges for larger support weapons like marksmen’s rifles and machine guns. As nations gained experience with the new small-caliber rounds, their disadvantages and limitations became more apparent. Most SCHV rounds from the 1980s on were optimized for penetrating power at ranges beyond the short-medium distance that the concept was originally designed for, sacrificing to one degree or another closer-range shock effect and “stopping power” (a term of convenience that remains too nebulous to truly define). In addition, despite incorporating tough bullet construction and armor-defeating steel cores that extended their nominal range, the effectiveness of these rounds at distances beyond 500m seemed to be significantly below that which was desired, and as a result every nation has kept in service older .30 caliber ammunition: The 7.62x51mm NATO in the case of the Western nations, and the 7.62x54mmR in the cases of Russia and China. This use of two rounds in tandem, instead of one universal one, was and is to many a suboptimal arrangement. In short, despite the resounding success of the SCHV concept, there was significant room for improvement.

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The current NATO caliber configuration, 7.62mm NATO on the left, 5.56mm NATO on the right.


4. Alternatives and their limitations

The immediate conclusion that many watching the problem came to was that the SCHV concept was inherently flawed; no amount of improvement within the existing chamberings would bring the ammunition to the desired level of effectiveness. Almost universally, these thinkers believe that the projectile weight of the 5.56mm round is too low, and virtually every would-be replacement caliber uses a heavier bullet, usually at lower velocity. We can group these proposals into two basic categories:

(A) includes the 6.8mm Remington SPC and the .300 AAC Blackout, and were designed around requirements to improve effectiveness from short-medium range only. As a result, these rounds typically have poor form factors and ballistic coefficients, and their advantages vs. 5.56mm diminish with range. Almost all utilize bullets over 100 grains in weight, with moderate muzzle velocities between 2,100 and 2,600 ft/s, and as a result typically have poor to mediocre trajectory characteristics. Together, this group essentially represents a line of thinking centered around replicating and/or improving upon the old Soviet 7.62×39 caliber, but for the existing AR-15 platform. As a result of their poor ballistic characteristics and substantially greater weight (25-50% more than 5.56mm), there is very little case for these rounds as standard issue military calibers, although they may be intended or adopted for specialized applications (e.g. subsonic .300 Blackout). However, this group has also received by far the most development, with military-style armor-piercing, ball, tracer, and other loads existing for both the 6.8mm SPC and the .300 Blackout.

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Left: 6.8mm Remington SPC. Right: .300 Blackout.


(B.) includes the 6.5 Grendel, .264 USA, 7x46mm UIAC, and several other wildcat cartridges, and represents an attempt to replace both 5.56mm and 7.62mm with a single round. Perhaps the most vocal proponent of this path is the British small arms author Anthony G. Williams, whose “General Purpose Cartridge” (GPC) concept he proposes as a unified solution for the infantry rifle squad. It centers around a medium-velocity (2,400-2,800 ft/s) round firing very low drag bullets of caliber between 6.2-7mm with the aim to create as efficient a round as possible with respect to recoil felt at the shoulder, overall cartridge weight, and delivered energy at longer ranges (beyond 800m), often with an emphasis on matching existing 7.62x51mm M80 Ball. The pitfalls of this concept are its substantially greater weight than 5.56mm (40-80% more), size (which also implies a larger weapon), and recoil, making the development of lightweight automatic weapons much more challenging. Further, the optimization of the round for such simple metrics as retained energy for a given size and/or weight carry with them potential compromises that may invalidate the concept for military applications, such as a low improvement in demonstrated effectiveness, incompatibility or poor compatibility with lead-free bullets, tracers, and other types of projectiles, and disappointing real-world ballistics resulting from “nickel and dimed” performance estimates during the concept stage. Although Williams sees this round as the clear unified small arms ammunition solution, it has so far not been been well-proven, and the weight disadvantage versus possible smaller caliber solutions remains largely unaddressed. Even so, if the adoption of a single round to replace both 5.56mm and 7.62mm is taken for granted, then Williams’ proposal does present the most intuitive solution. I discuss this concept in more pointed detail in posts on my own blog here, here, here, and here.

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Assorted longer-ranged intermediates. Leftmost is the 6mm SAW, designed to give better penetration to automatic riflemen in the US rifle squad. Middle-left is the Swiss 6.45x48mm GP80, an experimental predecessor to their 5.56x45mm GP90 round. The two rightmost: 6.5×38 Grendel, designed by Bill Alexander to improve the long-range performance of AR-15s.


5. Improving SCHV

In response to concerns about the lethality of both 5.56mm M855 and 7.62mm M80 Ball, the Army undertook a program to provide ammunition of superior effectiveness to the troops, which was fully compatible with existing weapons. The Marine Corps, too embarked on their own program to improve small arms effectiveness, and the results of these programs were the Army’s 5.56mm M855A1 and 7.62mm M80A1 EPR, and the USMC’s 5.56mm Mk. 318 and 7.62mm Mk. 319 SOST rounds. All four rounds utilized advanced bullet design based on extensive research to greatly improve the penetration and terminal effect – and especially the consistency of terminal effect – versus their predecessors. Further discussion about the “fleet yaw problem” these teams faced, and its solutions, can be read here.

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Improved 5.56x45mm rounds, left to right: 77gr Mk. 262, 62gr Mk. 318 SOST, 62gr M855A1 EPR.


Next generation solutions could also come in the form of calibers at or close to 5.56mm. The ogive space of the current 5.56x45mm envelope is decidedly not optimum, which limits how aerodynamic the bullets can be for cartridges loaded in that caliber. A cartridge that utilized a longer ogive length, akin to what Williams proposes for his 6.5mm round, could substantially improve performance versus the existing short-ogive rounds. A good example that exists today is the Soviet/Russian 5.45x39mm round, which achieves an 11% weight reduction versus 5.56mm, while giving slightly superior external ballistics. Projectiles more streamlined than even those of the 5.45x39mm are possible, too, which could be used alternately to save weight versus current 5.56mm or improve performance at the same weight or with minimal weight increase.


Two .224 caliber improved SCHV cartridges flanking a Williams-style 6.5mm GPC. The cartridge on the left matches the middle 6.5mm cartridge in muzzle velocity with a bullet of the same design, while being substantially lighter, while the cartridge on the right has a substantially flatter trajectory for the same heat flux. Both of the .224 caliber cartridges weigh within a gram of M855, while the middle round would weigh 40-50% more. All three cartridges were created and rendered by the author.


It’s commonly said in small arms ammunition discussions that “5.56mm is at the limit of its development”, but while that’s truer for the 5.56mm chambering as it exists today, it is absolutely not true for the .224″ caliber as a whole. By changing only the shape of the projectile to a lower drag one, major performance gains are possible, illustrated by the graph below:


Changing the bullet shape of M855 from one with a 1.15 i7 FF to one with a 0.90 i7 FF improves the performance considerably. The energy of the round with the lower form factor, shown by the red line, is the same as M855 for these range  values: 390 meters vs. 300 meters (M855), 650 meters vs. 500 meters (M855), and 1,000 meters vs. 770 meters (M855).


Future small arms ammunition engineers should take care not to ignore the potential of .224 caliber rounds to provide an effective, lightweight round.


6. The future

One thing not yet mentioned is very clear: For the moment, existing 5.56x45mm and 7.62x51mm ammunition (especially the new EPR and SOST series) is satisfactory, and a new brass-cased round of any kind is very unlikely to be adopted. The matter then turns to what the future small arms ammunition configuration should look like, given a paradigm shift like lightweight cased or caseless rounds. As much as we may want there to be, however, there isn’t an easy answer here; mentioned previously was the complexity of the problem, something that can only be worked through via thorough research and empirical testing. This groundwork, if yet laid, hasn’t been released to the public, and that sets a limit to the speculation amateur theorists like myself can confidently make. Key questions include whether the next configuration includes two rounds like the current one, or tries to unify them into just one, the answer to which depends on whether the logistical benefit of a unified round outweighs the increased load on the infantry of a heavier general-issue round. Also, determining the needs of the infantry squad, and how a new round fits in with their tactics, level of training, and inherent limitations is absolutely requisite: A round optimized for the best performance at over a kilometer does not do very much good if the soldiers using it are only effective marksmen out to a third of that. Likewise, a round with the best ballistics in the world doesn’t mean much if the empirical improvement in effect versus a smaller, lighter round is low. Conversely, adopting a round which is too short ranged or too weak, leaving the infantry at a disadvantage versus current and potential enemy individual weapons, should be avoided. Thus, great care should be taken in laying down requirements to achieve a solution that will give requisite effectiveness with the minimum weight.

Fortunately, the technology on the horizon is poised to assist with this last concern. The Lightweight Small Arms Technologies program was created to investigate lightweight weapons and ammunition, chiefly telescoped polymer-cased and caseless configuration cartridges. The telescoped ammunition concept is where the projectile is buried within the propellant, and then ejected from the combustion chamber in the earliest stage of ignition, therefore creating a smaller, more compact overall package. It comes with a number of nontrivial disadvantages related to barrel wear and propellant waste, which have been circumvented in the latest incarnation of LSAT’s Cased Telescoped Ammunition (CTA) by reducing the degree to which the projectile is buried in the case, and by fitting the case with a sealing gasket. Supplementing this effort has been conventionally-shaped composite (metallic/polymer) cased ammunition, as well as aluminum- and thin-walled steel-cased experimental configurations – this last having reached a high enough level of development to appear in the PEO Ammunition Systems Portfolio Book for 2013. These technologies offer weight reductions compared to current brass-cased ammunition of anywhere from 20-40%, savings that can be applied in varying degrees to either lighten the soldier’s load, or improve his effectiveness without adding weight. They all come with one caveat, however: Because they lighten the case of the cartridge, and no other component, they are not a magic mass-vanishing wand. The heaviest component of the loaded rifle cartridge is the projectile, so even lightweight ammunition must still be very carefully designed according to the same principles as conventional brass-cased ammunition to achieve the lightest possible weight for the desired performance.

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Lightweight ammunition is nothing new, but thanks to modern materials science it just might have a breakthrough soon. Here are some previous lightweight developments, left-to-right: .30 Light Rifle T65 aluminum cased, .280/30 British aluminum cased, 4.73×33 DM11 caseless.


7. To conclude

New technologies point the way for lighter, better small arms ammunition, but military outlets are interestingly quiet on the subject of the actual size and shape of next generation ammunition. There are benefits to both single- and dual-caliber systems, and any evaluation of the current and near-future state of the art must take both arrangements seriously. While the next ammunition configuration may not be publicly known, it is very clear that there may be serious consequences for carelessness in selecting a new caliber, especially in the case of the single-caliber concept. The adoption of the powerful 7.62 NATO in the 1950s, along with the troubled M14 rifle, created a need for a lighter, softer-shooting weapon that was eventually filled by the M16 and its 5.56mm round, which became the basis for today’s excellent M4 Carbine and its M855A1 round. However, in the rush to get rifles and a completely new type of ammunition to Indochina in the late 1960s, the implementation of correct standards and quality control were neglected, and many soldiers lost their lives as a result. The round, or rounds, that become the basis for the new generation of small arms will require a great collective labor of research and testing to achieve the best balance of characteristics and to avoid a critical gap in capability.


Nathaniel F

Nathaniel is a history enthusiast and firearms hobbyist whose primary interest lies in military small arms technological developments beginning with the smokeless powder era. In addition to contributing to The Firearm Blog, he runs 196,800 Revolutions Per Minute, a blog devoted to modern small arms design and theory. He is also the author of the original web serial Heartblood, which is being updated and edited regularly. He can be reached via email at


  • De Facto

    “making the development of lightweight automatic weapons much more challenging.”

    The US Military does not allow troops to use full auto, so this point is moot. I don’t know of any organizations that encourage or even allow the use of full auto, aside from the more aloha-snackbar spray and pray types.

    • Jay

      Full auto fire changed the nature of warfare more than most small arms innovations.

      • De Facto

        FA from LMG’s, yes. Not individual rifles. USMC/US Army do NOT allow troops to even use 3 round burst, let alone FA. LMG’s are their own animal, equating a M240/M249/50 BMG with an M16 or standard infantry rifle is disingenuous.

        • politicsbyothermeans

          You can pick almost any firefight video from Afghanistan or Iraq and see Americans firing in burst or auto from select fire weapons. Are the Air Force and Navy allowed to use the giggle switch, or just Marines and Soldiers? Where is the order or regulation stating that burst or auto isn’t an option?

          • John

            Although I don’t agree with De Facto’s argument, I don’t think referring to firefight videos is a valid point. After all, people called the full auto switch the panic switch. Regulations go out the window when in combat

        • Jay

          The latest military version of M4 removed the burst setting and went back to the traditional Safe,/semi/full auto configuration. On top of that they also added a heavier barrel.
          That should tell you everything you need to know.

          • toms

            The Switch is there but its use is not encouraged nor do people who really use their arms a lot use full auto outside of support weapons. Its really just a cool morale booster. The m27 is an exception but it is used as a suppressive/support weapon. A lot of SOF will tell you they never used full auto outside of training. Its pretty useless, just burns up limited ammo supplies. The new heavy barrel is for sustained accurate fire not full auto. Other countries use it like Russia but not NATO armies in general.

          • Joshua

            Yes, that the RO921HB has better accuracy and barrel life due to the more rigid structure of the barrel and that the S-1-F trigger increases accuracy by having one consistent trigger pull vs the S-1-3 that has a cog that has multiple different trigger pull weights that vary depending on cog location and reduces accuracy.

            No one uses the full auto setting, yes it’s there but in general combat firing on semi auto is far better and far more accurate.

        • El Duderino

          Neat. I’ll throw away my Combat Marksmanship Course cert, where we did exactly that (3 round bursts). If you aim at the kidney you can put 3 rounds in a diagonal line across the torso at 25m. Done it. It has a purpose, and that is killing people at bad breath range.

    • CommonSense23

      Let’s see , M249, MK43, MK48. All weapons that are full auto only and often shot standing from the shoulder.

      • De Facto

        You mean those guns with bipods designed primarily for use from the prone position?

        • CommonSense23

          Considering the MK43 and MK48 were specifically designed for shoulder fired use, and the saw see heavy shoulder fired use, yeah those weapons.

          • De Facto

            Yes, they CAN be fired from the shoulder or hip, but are cumbersome, heavy, and much less effective when used in that role.

          • CommonSense23

            The MK43 and MK48 were specifically designed for that role.

    • politicsbyothermeans

      Uhm, what? The merits of well-aimed semi-automatic fire over burst/auto notwithstanding, it is not at all true that the US military doesn’t allow servicemembers to use automatic. A great number of weapons systems are ONLY automatic.

      • De Facto

        Full auto weapons such as the M240/M249 are not what I’m referring to. Individual rifles are. Crew served weapons and LMG =/= infantry rifles

        • politicsbyothermeans

          So you’re saying that there is some sort of regulation or standing General Order forbidding automatic fire in select fire individually assigned weapons? Because I’m telling you there isn’t. American servicemembers are absolutely “allowed” to utilize the full functionality of their individually assigned firearm, including select fire.

          • sauerquint

            You’d think if wasn’t ‘allowed’ the rifles wouldn’t have the selector. Or that the military would not have transitioned from the m16 to the m4 at all. ‘De Facto’ is digging in his heals and stamping his little feet in absolute defiance of observable reality.

          • John

            Well, technically there is for certain situations listed below

            TM 9-1005-249-23&P, Page 4-4
            The lock plate prevents the selector from being placed in AUTO and will be installed at the discretion of the unit commander. It is mandatory for use in civil disturbance (riot control)

        • Sgt schmegma

          Ever heard of the M4A1?

        • Luke

          The USMCs adoption of the M27 as an automatic rifle by the individual Marine puts paid to that argument. Here you have a weapon that is designed to be fired from the shoulder and is used primarily as a full auto weapon.

          • toms

            It also comes standard with a Bipod. Full auto fire is not encouraged or particularly useful. M27 is a support weapon. Its not illegal but well trained soldiers do not use their M4’s in full auto except in rare situations. Its not really effective and burns up limited ammo supplies

          • Luke

            True, but it still is an individual weapon, and its users are trained to fire it on full auto. No one who is trained to fire a fully automatic weapon will just pull the trigger and hold it. Instead, they will use a cadence to fire short bursts.

            When the Army did a field test with the 5.56mm LSAT LMG they found that MP soldiers that were firing the weapon found it very controllable when firing fully automatic from the shoulder. The way that the action works helps t remove a lot of the muzzle climb, so it is much easier to stay on target.

    • 6.5x55Swedish

      Any nation that spend more than 8 minutes of training their troops make sure they know how and when to use full auto. No wonder you lose every damn war, sending soldiers to war that doesn’t know how to fight can never be a smart idea.

    • “Automatic” in this case refers to either semiautomatic, select-fire, or fully automatic weapons.

    • gunsandrockets

      I think the point is well made that 21st Century doctrine de-emphasizes fully automatic fire from service rifles compared to what was desired during the 20th Century.

      • El Duderino

        Sure. Middle of the 20th century doctrine (particularly Soviet) was to keep their heads down with small arms fire and drop indirect on top of them.

        Too many bad guys have learned that U.S. forces won’t drop ordnance on civvies, so they intersperse and now you MUST use aimed fire to take them out. Different deal.

    • toms

      Russians do maybe the Chinese too.

  • Jay

    Good article. Thank you.
    The Russians did get the cartridge shape right with the 5.45×39. Very well designed cartridge for it’s intended purpose.

    • Mark

      “The ideal round kills instantly with one shot…” Really? What happened to the doctrine of wounding to tie up more of the enemy’s manpower and material in caring for the wounded?

      • So far as I know that has never been US military doctrine for small arms ammunition.

        • Mark

          Then why was it expounded by the Founder and Director of the US Army Ballistic Research Laboratory?

          See: Fackler ML, Malinowski JA, Hoxie SW, and Jason A. Wounding effects of the AK-47 rifle used by Patrick Purdy in the Stockton, California, schoolyard shooting of January 17, 1989. Am J Forensic Medicine and Path. 1990; 11(3): 185-90.

          • I am not saying no one ever said it. I am saying that the Army has never had that as its operational policy, so far as I am aware. The closest they come is with M855, which had a somewhat schizophrenic sales pitch involving it being both more lethal and more humane than M193, but that was a Belgian-designed bullet, not an American one.

            I just re-read Fackler’s paper, since you cited it, and he says nothing of the sort in there. In fact, nowhere does he talk about military doctrine at all. You appear to have cited a paper at random.

          • Mark

            Here is Fackler again: “Military full-metal-jacketed bullets, such as those used on the Stockton schoolyard, are designed to limit tissue disruption — to wound rather than kill. In warfare, this bullet is effective: it removes not only those hit from the ranks of the combatants, but also others needed to care for them.”,%20Stockton%20case.txt

          • And Fackler set military doctrine? News to me!

            Military rifle bullets are designed to be compliant with the Hague Convention of 1899, and they are also designed to defeat barriers (chiefly helmets) and be as cheap as possible. Until recently, none of these things were particularly compatible with being extremely terminally effective.

            Now, are you going to sit here and try to tell me that Mk. 318 or M855A1 were designed to “wound, not kill”?

          • Mark

            I asked a simple question wondering what happened to the doctrine of wounding rather than killing, a doctrine that is indeed stated in the medical literature on wound ballistics. You said you never heard of the doctrine. Now you have heard of it. Perhaps the doctrine has changed (as indeed this nation has changed), but I will take the professional expertise of an experienced and world renown physician and a military lifer over a hobbyist with thin skin.

          • It was never doctrine. You cited a medical doctor offering his opinion. Fackler had nothing to do with setting doctrine, he was experimenting with methods of wound ballistics testing.

            As for me having “thin skin”, um, alright. Whatever helps you sleep at night. I’m not offended by what you said, it’s just wrong.

          • Mark
          • What is this, a form for ants?

          • Cal

            Cockroaches. I’m cockroach kin and this is too small.

          • CommonSense23

            I have had 06 Jag officer try and tell me we couldn’t legally shoot people with 50cal cause of the Geneva Conventions. Be real careful taking single opinions from guys who are talking about something that is well outside their lane.

          • Mark

            I was careful. I asked, but the thin-skinned hobbyist who admits he never heard of the doctrine took it as a personal affront. Go figure.

          • CommonSense23

            And what Fackler stated was not army policy or doctrine. Its something he came up with on his own. The idea that you couldn’t legally shoot people with 50cals was something that was taught to officers for a while, didn’t mean what was being taught was correct.

          • Mark

            How do the Hague Conventions fit with this? Apparently numerous nations agreed that some behaviors and weapons were unacceptable even in war.

            I realize that the United States was not a signatory to all the elements of the Hague Conventions, but evidently some nations had moral qualms about certain behaviors and weapons. Judging from the content of the Hague Conventions, the doctrine of some nations was NOT to engage in kill-em-all rampages. Those nations appear to be in accord with just war theory.

          • CommonSense23

            Have you actually looked into what the Hague conventions was about. Or how none of the signatories just magically stopped using expanding munitions on non signatories.

          • Mark

            Yes, I reviewed the Hague provisions. As far as compliance, I glossed the outcome (poison gas in WW1, firebombing in WW2, use of armed balloons, etc. I am reasonably knowledgeable about history, but I am definitely not a military historian except as it touches on crimes against humanity.

          • Mark

            “[S]omething that was taught to officers for a while”—Wouldn’t such curriculum derive from policy approved by higher authority? Or was the teaching from some rogue elements?

          • CommonSense23

            It came from a misunderstanding from a written field order, that was tactical in origin, and had nothing to do with any laws or ethical reasons.

          • Where did I take this personally? Please, cite the line you feel negatively about.

            You’ve had a minor reading comp issue. I didn’t say I’d “never heard of the doctrine” (well, it’s not a doctrine, so I can’t have heard of it as such, but I get what you mean). Here’s what I actually said:

            “So far as I know that has never been US military doctrine for small arms ammunition.”

            That’s not “I’ve never heard anyone say that before” that’s, well it’s self-explanatory, really.

            At no point have I felt even the least bit emotional about this subject. On the other hand, you seem to have reacted very strongly to someone proving – or from your perspective, attempting to prove – you wrong. It’s gauche to be an Internet psychologist, I know, but the immediate word that comes to mind here is “projection”.

          • Mark


          • Oh yeah, you’re a real gas buddy.

          • n0truscotsman

            and Fackler is dead wrong. Simple.

            As indicated by the mountain of stuff he was wrote over the years, it seems he has an axe to grind with the 5.56 in general.

            I’d really like to know the ‘wound rather than kill’ argument’s original history, where it came from, who said it, etc.

          • Mark

            …and that is precisely why I asked. It has been stated as a doctrine. Is it doctrine? If it is/was a doctrine, has it been superseded? As best I read what is available, there was a POINT to the Hague Convention that outlawed ammunition that was perceived as particularly lethal… but that came from a time when Americans didn’t justify torture, bombing wedding parties where most are innocent, firebombing entire cities of non-combatants, cackling gleefully that your enemy was sexually abused, etc. Perhaps the doctrine changed because America changed.

          • It was never doctrine. After you mentioned it, I asked friend of mine with brass on his shoulder about it, and he agreed with me, although frankly I didn’t have any doubt.

            The Hague outlawed bullets that they felt caused undue suffering, not those that killed. The spirit of the Hague was “kill them stone dead, instantly”. Exactly as I said in the paper, in fact. Here’s what the 1907 agreement says, which the US did sign:

            “…it is especially forbidden –

            To employ arms, projectiles, or material{sic} calculated to cause unnecessary suffering;”

          • n0truscotsman

            It hasn’t been ‘superseded’ because industrial output and ammunition capacity has evolved to where you can produce rounds like the EPR, which are a step above plain ol FMJ in terms of lethality. Its a testament to the times I suppose. Consider that specialized ammunition (like match) has a long history of military usage, and its military use has directly correlated with developmental trends throughout the decades.

            “but that came from a time when Americans didn’t justify torture…”

            Um things weren’t ‘better’ back then, in fact, they were far worse. Examine historically controversial chapters in American history such as the Philippine insurrection, Wounded Knee, etc
            before you attempt to claim that we are somehow worse now (which I find very hard to believe).

          • Mark

            It is only since the 20th century that “we” managed to kill millions in a short time. Since I disagree with Stalin’s morality, I do not view that as a “statistic,” but a tragedy. Not merely a “claim,” we are worse as a nation.

          • n0truscotsman

            So with the major and minor media outlets, the internet, and substantial publicity, we are somehow ‘worse’ as a country when it comes to committing war crimes?

            yeah, BS. government incompetence cannot even go unreported, let alone deliberate killings like what occurred long ago.

            This is a funny conversation too since I have little respect for US foreign policy and interventionism in general.

          • Mark

            Your impatience is irrelevant.

        • Monty01

          Nor a UK doctrine. Nor a German doctrine.

      • Major Tom

        None of our enemies cared about tending to their wounded on the battlefield. That’s what happened. Instead they foisted em upon us to care for.

        • Mark

          It is a good thing that the VA Hospitals provide such excellent care to American vets.

      • n0truscotsman

        That is mostly horse crap tbh.

        And militarily short sighted.

        Killing and severely incapacitating a soldier keeps him out of military service, whether through death or disability, which means another soldier has to be re-trained to replace him (money and time). If this is the case of an experienced NCO or officer, who has committed 5-10 years of peacetime training, or previous combat experience, you are talking about a significant loss in that unit.

        wounded soldiers who are able to recover may have had one or two friends carry him off the battlefield, although he will probably return to full duty of his wounds aren’t too egregious (FMJ typically).

      • MPWS

        This is a premise on which small caliber ammunition (aka 5.56) was allegedly based. Where is it?

        My own question: why to kill enemy? Same rational as before. After heat of battle he can actually become your fiend. Less waste of effort and substantially more benefit! But I realize, as long as military stalwarts will drive this thing, there will be no progress.

      • Brian M

        No military man ever thought, “Gee, I would really love to just WOUND all these sumbees trying to kill my friends and I. That would really tie up their logistics something fierce.”
        A kill is better than a wound. Dead soldiers can’t be employed on the homefront, dead soldiers can’t supply intel, dead soldiers can’t speak at propaganda events, dead soldiers can’t shoot you in the back, dead soldiers can’t pull grenades, dead soldiers don’t leech your supplies to care for them,

        • Mark

          I have cited one military man, a lifer, a world-renowned surgeon and researcher, who expressed exactly what you insist no military man ever thought.

          Again the questions are whether it was official doctrine, a majority opinion, a minority opinion, a doctrine that changed, held by some nations, but not others, etc. ?

          So far I see personal opinions and speculation by hobbyists. Are there any official documents? If so, I am interested.

          • I have never seen it in an official Army document pertaining to doctrine. Neither has anyone else. What more do you want?

          • Mark

            That was precisely what I wanted to know. Thank you.

          • No, that’s just my opinion, and just used to illustrate the often mutually exclusive requirements of small arms ammunition, when not taken out of context.

          • El Duderino

            There’s not much more to add here, but the “wound vs. kill” has been mantra for decades. I heard it in the USMC in the 90s. No it’s not doctrine. Neither is Murphy’s Law, but it gets shared in briefs and training.

            While neither 5.56x45mm or 7.62x51mm are optimal chamberings for their envelope, the tiny gains achieved through tweaking won’t move any mountains within the DoD. It’s akin to the “pfft 9mm I carry a .40″ argument. There are performance gains on paper but very little in the field.

            As a weekend warrior I’d love to carry a 6.5 Grendel 18” AR into combat…but it’s never gonna happen.

          • Can’t really say anything about the USMC, as I’ve studied them far less. Doesn’t surprise me that there’s overlap with that particular piece of civilian scuttlebutt, though.

            Also, keep in mind that the context was the design of infantry small arms ammunition, something the USMC traditionally does not do.

          • El Duderino

            I don’t think it began as civilian scuttlebutt. Most likely someone in the Army or Marines started harping on it during the Cold War and it just sort of became “common knowledge”.

            As for the last statement, that’s historically true, particularly in the 20th century. The USMC was allowed to be a lot more inventive in-house from 1775 to WWI when they transitioned from small scale warfare to the trenches…though in the interwar years they did slide back away from “Army weapons” somewhat. You’re starting to see the USMC/USN slide away from the Army again.

          • Mark

            Then you had better also carry a bag of replacement Grendel bolts

      • LilWolfy

        It’s barracks lawyer fallacy. The focus of the SS109 was to penetrate Soviet body armor and light skinned vehicles expected to be encountered in that era.

        • Mark

          I’m sorry. I’m unsure what you mean, what the lawyer of the Kenyan bathhouse boy has to do with SS109. Are you referring to the recent effort to ban civilian ownership of SS109/M855?

  • 6.5x55Swedish

    Nice to see the 8×63 Bofors. It really sucks that no company have picked it up for the commersial market. I’d love to use it in a pig gun. It is a really interesting round, you should write an article about it.

  • Nicholas Mew

    “every nation has kept in service older .30 caliber ammunition: The 7.62x51mm NATO in the case of the Western nations, and the 7.62x54mmR in the cases of Russia and China. This use of two rounds in tandem, instead of one universal one, was and is to many a suboptimal arrangement.”

    The most curious wildcard though would be the Soviet 6x49mm Unified Catridge for GPMG and Sniper Rifle use. The Soviets appeared to be very keen on replacing the 7.62x54mmR and the weapons that used that caliber. I am curious as to what others think about it because it is interesting what they were thinking and planning on doing until the breakup of the USSR put that on indefinate hold.

    • Anonymoose

      The PKM is still pretty great compared to comparable light machineguns, but the mechanism in all 7.62x54R MGs is has to be convoluted to deal with the rimmed case. Rims have always been a major problem in small arms design outside of single-shots, revolvers, and pumpguns. The whole reason for giving the Mosin cartridge a rim was to allow the old Berdans to be rechambered for it too. In a (box) magazine-fed gun, that can often lead to jams and in semi- and full-autos is a real pain in the butt, especially when you have to pull it backwards out of the belt before chambering it.

      • marathag

        Still got 1800 RPM from the ShKAS, and its rotary delinker.

      • Nicholas Mew

        The fact that they got many weapons to work reliably with the 7.62x54mmR is amazing and a testament to their design genius though.

  • Hokum

    As always – very good article! Especially with the numerous links included.

  • iksnilol

    I am still waiting for a 4.5x35mm round.

    Take the 5.56 another level forward.

    • Jay


    • gunsandrockets

      What? No love for the .204 Ruger? IMHO that is the SCHV concept taken to the next level. And even better, the .204 Ruger is easily compatible with the existing AR infrastructure.

      • Vitor Roma

        I read about it and it is quite impressive indeed. The 45gr is about 1100 meters per second, they could make a heavier one with higher bc and about 960m/s that still is plenty of fast.

        • gunsandrockets

          A heavier bulleted .204 Ruger? Essentially you are talking about the British 4.85mm cartridge. You could do that, but I think that approach just muddies the waters.

          I think it makes more sense to just accept that a SCHV cartridge is not a long range cartridge, and design it for maximum effectiveness up to 300 meters.

      • iksnilol

        It actually looks good.

        Can we somehow neck it down to some ultra long 4.5mm bullet (and shorten the case appropriately)?

        • ostiariusalpha

          No need to shorten the case if it’s in a case telescoped cartridge. LSAT or its successor is going to make a whole new paradigm possible.

        • gunsandrockets

          Depends on what you are after. I think the .204 Ruger is fine as is, and is the true embodiment of the SCHV cartridge concept. SPIW tried to push the velocity envelope beyond what was practical.

          • iksnilol


            But seriously, .204 Ruger looks cool.

          • ostiariusalpha

            Longer bullets are usually slower, in reality. You’d be looking at more retention of velocity for improved armor penetration and terminal performance at that 300m engagement limit.

          • gunsandrockets

            Did you mean to post “longer bullets are usually faster in reality”?

            And longer bullets obviously don’t come for free.

            What we are talking about is really the contrast between a cartridge like the 5.45mm and the .204 Ruger. One cartridge with a long efficient bullet but small powder charge, the other cartridge with a big powder charge but small mediocre bullet.

            Is the 5.45mm superior at 300 meters? Perhaps. But it is definitely inferior at closer ranges compared to the .204 Ruger. I think the entire envelope from 0-300 meters is important and what a SCHV cartridge is best at.

          • ostiariusalpha

            LOL! I thought you were kidding! Are you really not aware that the lighter a bullet is, the faster its muzzle velocity? That’s like Ballistics 101 stuff.

      • Marcus D.

        Why not .22-250 with the M855A1 bullets?

        • gunsandrockets

          Sure you could get better range with that, but with quite a bit of penalty in increased size, weight, and recoil compared the .204 Ruger.

          In addition, will any existing 20+ round magazine work with .22-250, or will it need a new unique magazine?

          • Marcus D.

            I doubt any existing mags work with .22-+250 since its OAL is slightly longer than .223. But the recoil of either .22-250 and .223 is essentially negligible in an AR style platform. What you get is increased range and velocity at minimal if any noticeable increase in weight compared to .223. With the M855A1 bullet, you get the stability and lethality that was always lacking in the AR platform.

            To add one off topic comment, one of the things that will be changing the battlefield is the use of magnified optics. I think we will be seeing–and needing–more of that, particularly at 500+ meter ranges that we are now fighting in Afghanistan. Although red dots have great utility at a few hundred yards, at range they are no better and perhaps worse than good iron sights since they completely obscure the target at extreme range, leaving us in no better, and some would say worse, position than the enemy lobbing 7.26 at us from out there with iron sights.

          • gunsandrockets

            When I was comparing cartridges, I was comparing your proposed 62 grain bulleted .22-250 cartridge vs a 45 grain bulleted .204 Ruger. The .22-250 would have at least 35% more weight and recoil.

            In addition the extra size of the .22-250 cartridge would compel use of an AR-10 sized platform and magazines.

            If 500+ meter range fires are so critical for standard rifles (and I don’t think it is) I don’t think any SCHV cartridge is what you want to get that. A cartridge like the 6.5mm Grendel is a better choice.

          • Right, I would say for the GPC/Grendel people reading, I don’t really disagree with their conclusions given their premises, I just question their premises and assumptions.

            I have a very hard time justifying a rifle cartridge optimized for those kinds of ranges, given the current level of marksmanship imparted onto our riflemen. That’s a truth that a lot of people don’t want to face, too.

          • M855 and M855A1 weigh 12 grams a shot.

            .22-250 has a case slightly lighter than 7.62 NATO’s case, so we can give an off-the-cuff estimate of its round weight with a 62gr bullet. 7.62 NATO weighs about 24.2 grams a shot, so subtract from that its 9.5 gram bullet, and you get 14.7 grams for an empty case. Now, the .22-250 case is somewhat lighter with somewhat less propellant, so we’ll take away 0.8 grams for the propellant, and let’s call it a half gram for the shorter necked down case. That leaves us with a 13.4 gram case. Add to that a 4 gram bullet, and you’ve for a cartridge that weighs 17.4 grams, or 45% more than 5.56mm.

            So not at all “minimal if any noticeable increase in weight”.

        • Barrel heating and wear would be absolutely off the hook.

          • Marcus D.

            The .22-250 is only 300fps faster than .223 using a 62 grain bullet (3550fps v 3250 fps for the M855A1), and the M4 has already gone to a heavier profile because of heating issues. Obviously the .204 would be far worse.

          • M855A1 muzzle velocity is 2,970 ft/s from a 14.5″ barrel, 3,150 from a 20″ barrel. At this performance, Powley calculates it to have a 33.5% efficiency.


            .22-250 loaded with the bullet of M855A1 and fired at its SAAMI PMax of 65,000 PSI has, according to Powley, an efficiency of 28.7%. At this pressure, it produces 3,561 ft/s muzzle velocity.


            So, to calculate heat flux, we find the wasted energy of both rounds:

            M855A1 effective energy: .5 * 4g * (960m/s)^2 = 1,845 J

            .22-250-A1 effective energy: .5 * 4g * (1,086m/s)^2 = 2,357 J

            Wasted energy is effective energy times (1-e)/e, where “e” is the efficiency in decimal format:

            1,845 J * (1 – 0.335)/0.335 = 3,662 J wasted energy

            2,357 J * (1 – 0.287)0.287 = 5,856 J wasted energy

            That energy gets wasted as heat, but the amount of surface area in the barrel to soak up that heat matters, too. However, both these numbers were calculated for cartridges fired from 20″ barrels with .224″ bores, so the next step (which would be dividing by the square of the bore diameter times the bore length), is unnecessary. We can simply ratio the .22-250’s wasted energy over M855A1’s wasted energy, to determine that a single .22-250 would dump 60% more wasted heat energy into the barrel of the gun per shot than 5.56mm. If the rate of fire of the weapon is kept the same, that’s a huge increase in the amount of heat being dumped into the barrel, and would result in catastrophic weapon failure much, much earlier than for M855A1.

    • Joshua

      I’m wanting a 2mm gauss rifle that flings projectiles at 10,000+FPS.

    • Phil Hsueh

      Forget that, I’m waiting for the caseless 10mm, armor piercing, explosive tip round to come to fruition along with the M40A1 Pulse Rifle to fire it.

  • TechnoTriticale

    There are other serious constraints on anything that might look promising. One, already hinted at, is the Hague Convention.

    Another is transition issues, or as we used to put it in the computer industry: it was easy to create the world in 7 days, because there was no installed base.

    Any new round must not create an interchange hazard during the transition. Jam, click and kaboom are all hazards.

    Is the new round constrained to fit through an M4 mag. well? This is primarily an OAL issue and a major limiter on improving the aerodynamics of current configs.

    Is the new round constrained to use existing STANAG mag. wall ribs? Mag interchange hazards could arise as an issue too.

    • Absolutely. I was already pushing 4,000 words (ended up at about 4,100), so some subtopics had to be left for another day. In fact, I’ve got a post on tracers coming out tomorrow that used to be a few paragraphs in this post!

    • Luke

      The US isn’t a signatory to the Hague Convention. We make our ammunition compliant with it voluntarily, and we want to be able to supply it to our allies who have signed it. What many people forget is that in the wars that we are fighting today, the Hague rules don’t actually apply. The rules are very specific that they apply only if BOTH sides in the conflict have signed it. It was really meant for wars between European powers, not when a non-state actor is involved.

      As for an interoperability, other than what we have seen with M855A1 and MK318, I don’t think that you are going to see a new round get adopted that is substantially different, and certainly not in a new caliber unless are getting new rifles to go along with it.

      • Mark

        Since the US is already fielding laser weapons, including blinding lasers, what are the prospects for a new standardized cartridge? Slim?

    • Paul White

      as someone with (limited) IT experience that’s handled a couple of migrations, I think folks underestimate the absolute hell out of the transition problems.

      It’s like replacing the AR; there are certainly designs that are *probably* better but are they better enough to warrant the expense of re-equpping our armed forces and retraining people on them? Ditto cartridge choice; is there something that’s clearly better enough to warrant a new weapons platform and all that jazz?

      • El Duderino

        It’s actually bigger than just a platform. Leaving 5.56mm AND 7.62mm for New Cartridge X means a very long list of small arms either get overhauled or thrown out.

        Nations with small forces and tight logistics can actually get away with a greater spread of calibers than the U.S. can. Imagine needing a boutique caliber available in quantity for every base, post, camp, JSS, OP, etc!

  • aka_mythos

    Very good article. I’d be interested to see a similar article on the development of powders and their impact on ammunition.

  • That is not the same cartridge as the 6x45mm SAW, it’s instead a wildcat of .223 used in competition and hunting.

    The civilian 6x45mm has been suggested as a military round, but it honestly doesn’t really offer anything more than 5.56.

    • Brunswick reportedly used a 6mm/.223 Remington wildcat in their unsolicited submission for the 1970s Squad Automatic Weapon trials. I presume that this patent shows their SAW.

    • Fegelein

      ” it honestly doesn’t really offer anything more than 5.56″

      You say that about everything, even when the numbers show that something is superior, like 6.5 Grendel and 6.5 Creedmoor.

      • From the article you’re commenting on:

        “[Caliber configuration] is complex subject, with few easy answers, and is often erroneously reduced to a matter of ballistic “performance” without regard for actual real-world effectiveness and balance.”

        None of that changes the fact that 6x45mm is an almost identical round to 5.56x45mm, and has virtually the same performance, either.

  • Aaron E

    You did an excellent write-up Nathaniel! I know TFB tends to want to push out as much information as quickly as possible, and that usually ends up in 200-500 word posts. Every now and then its great to get an in-depth study on a topic.

    This one was informative, easy to read, and had all the necessary links to support statements or conclusions. Well done, and look forward to the future posts.

  • CommonSense23

    If anything is going to cause a drastic change in were calibers are heading. Its going to be armor. Precision guided munitions have already reached the individual level at the SOF level. And they are going to be heading to conventional side soon if they are not already there. There isn’t going to be much of a need for a 600 meter plus round when you can have two hand held cruise missiles slung on your back.

    • toms

      Yes! This is something the US has not been following up on very well. Russia and some other countries are already fielding gear we couldn’t poke a 5.56 hole in if we wanted too, and are also issuing ammo that will zip through level 4 like 7n39. A little hole is better than no hole at all. Flechettes or explosive rounds are the future.

    • n0truscotsman

      I couldn’t agree more.

      This is why I have grown increasingly antithetical to the GPC concept, initially being a big fan of it.

      IMHO we haven’t become ‘closer’ to adopting one, but rather, increasingly more distant.

  • gunsandrockets

    Muzzle blast problems experience with the SPIW project demonstrates some important issues and limitations of HV cartridge concepts.

    • El Duderino

      Yeah, it definitely SPIWed too much at the muzzle.

      • MR


  • gunsandrockets

    As gun people we tend to obsess too much over the trivia of cartridges and individual rifle design compared to their actual importance in the scheme of real military power, which ranks those issues at the bottom of the barrel.

    Even so, trivia is fun!

  • TheSmellofNapalm

    This is my current wishlist, along with the cartridges I’ve selected for each rifle:

    1. Suppressed .300 BLK SBR
    •Lehigh 110 Controlled Chaos

    2. Precision 5.56 SPR
    •Black Hills 77 Tipped MatchKing

    3. Bolt-Action 6.5 CM
    •Hornady 143 ELD-X Precision Hunter

    • mig1nc

      Very nice choices. That’s also what I’m re-configuring to. With a can on each one also. Although, the new Hornady 75gr TAP-SBR has me intrigued.

  • Fantastic article!

    One interesting question is how the XM-25 and similar weapons will effect infantry fighting, and subsequently the needs of the rifleman.

    For example, if the XM-25 proves to be as excellent as designed to be (ie complete dominance from the 50-500 yard zone) then that could radically shift the needs of rifle/lmg cartridges. If the doctrine becomes “hold their heads down for a few seconds then airburst grenade them” then an LSAT 5.56 or even lighter cartridge (4.6×36, etc) would work well for suppressive fire and room clearing CQB, and the needs of actual rifle cartridges would likely shift to optimizing effectiveness at 500+ yards for enemies beyond the reach of the XM-25/LMG combo.

  • nova3930

    good article.
    1. any gpc is necessarily going to be compromise. i think for that category of cartidge the first step is for the user to decide which attributes they wish to optimize for. till you have the user requirement I’m not sure you can generate an optimal solution.
    2. I think 556 is at the limits of it’s development, in the AR platform. just off the cuff I think you could gain a little bit more if not constrained by the OAL limits of the AR magwell.
    3. I think that a possible option in the future is partially caseless configurations similar to what you see on 120mm tank rounds. even just having the metallic case head can eliminate some of the issues associated with full caseless ammo while shedding weight.

  • Tassiebush

    Good write up! A lot of ground has been thoughtfully covered in choosing trade offs that the current platforms are. It’s a challenge working out how to move forwards from that without losing ground.
    I am curious about what the stumbling blocks were/are with fletchets and sabots. That xm216 round looks like a dream. It’s a shorter narrower case which presumeably shoots on a very flat trajectory with less recoil potentially from a gun with a bigger mag capacity and a shorter action.
    It’d seem to have the makings of cheap ammo too using less brass and smaller metal projectiles.
    I also wonder if the notions from the SALVO project could be dusted off. The ideas around super fast bursts, duplex rounds or small volleys from multi barrel weapons seemed to achieve superior first shot hits albeit at considerable weight and recoil costs.

    • I think the biggest problem with flechettes is their very poor permanent cavity characteristics. Having said that, they have great velocity retention and penetration for their projectile weight, so perhaps they’re appropriate for some kind of PDW or something.

      • Tassiebush

        Makes sense about cavity size. If you hit the enemy but they keep fighting regardless it’s not doing the job. I recall reading somewhere that the tail fins tend to dictate the permanent cavity size although that was with shotgun fletchettes which’d be substantially slower than rifle ones so in that instance it’d be behaving like a pull through broadhead.
        I sorta think fletchettes coupled with multiple hits could hold more promise whether that’s a hyperburst or triplex rounds or something of that ilk because you have the greater chance of a hit and the flattened trajectory, but then i guess you start adding weight and recoil since you have to treat the combined fletchetts per shot/burst like a single conventional round.
        Perhaps the plan for fletchette success is to emulate the WW1 french idea of dropping a bundle of steel darts from a plane but use a drone instead lol!

      • George

        Perhaps for longer range suppressive fire, where penetration (vs wounding/lethality) and range and flat trajectory (and lower precision accuracy if you use cheap fins) are tolerable.

        GPMGs don’t really need heavier bullets and cartridges – they need the range.

  • Dave

    Excellent essay, Thanks!

  • McThag

    I had to sit down and read this post three times before I could get my knee-jerk response under control well enough to actually READ this post.

    Glad I gutted it out.

  • gunsandrockets

    How cartridges behave in an urban environment is something frequently overlooked.

    I’ve read that supposedly during the Grozny city fighting the Russians experienced inferior performance from 5.45mm cartridges compared to the older 7.62x39mm in penetrating typical urban cover.

    I remember seeing this old video, so I googled it up. It’s from 2008.

    • I dunno about the Grozny experience, but in the case of 7.62×39 compared to 5.56mm, I’ve found in informal testing I conducted years ago that that was more a matter of bullet construction than anything else, at least when talking about pine boards and cinder blocks. When I used steel-jacketed FMJs for both, they penetrated about the same.

      • gunsandrockets

        The same mechanism which gives the 5.56mm greater lethality than the 7.62x39mm at short range also harms it’s penetration vs urban cover at short range. I think it’s a good lesson in TANSTAAFL.

        • CommonSense23

          Be really interesting to see that test with modern munitions.

        • Yep. It’s a tradeoff, but one that more recent projectile designs greatly improve upon.

  • Spock

    I have a SIG MCX that can shoot three cals: 5.56, 7.62 Russian and 300BLK. I was comparing the 5.56 one day to my Garand’s 30-06. The 5.56 seemed like something you’d see fired from a small weapon against varmints.

    I’ve spoken to vets who talked about the 5.56’s ineffectiveness. They preferred the 6.8 since the .308 wasn’t available in their AR platform. We won WWII with long rifles chambered in 30-06 FMJ. Our GI’s carried all that ammo with them from town to town. Holding an M1 Garand gives a man confidence knowing the 30-06 can reach out with accuracy while also penetrating easily. The rifle is balanced and comfortable to shoot like its M14 cousin, though its 26″ barrel is long. The 30-06 and the shortened .308 round, are both accurate and have good penetration. The recoil is stout but in the heat of battle, would any man come away saying, “Wow I miss that 5.56 or 6.8.” I’d wager not.

    The .308 has been adapted to AR’s for a while now using DI or piston effectively and reliably in 16″ barrel lengths. Most vets say that the .308 is just lights out. Given the choice, the .308 is the round I’d feel most secure with. Why not develop something else from there?

    • CommonSense23

      What vets you know of who have experience with the 6.8.

      • Spock

        A Marine.

        • CommonSense23

          A US marine was using a 6.8 in the military?

          • Spock

            Did I stutter?

          • CommonSense23

            Well the only supposed field use of the 6.8 by the US military was conducted by members of SOCOM. And considering Marsoc was not a part of SOCOM when that field use happened. Find it hard to believe a Marine would have access to 6.8. Do you know what unit he was attached to?

          • Spock

            Let me try to understand this. Are you calling me or this veteran a liar?

          • There are other ways to be wrong besides lying, mate.

            I too think it’s prohibitively unlikely that your buddy ever used 6.8 SPC in combat.

          • CommonSense23

            Considering the Marines wouldn’t be responsible for testing a SOCOM round. There is absolutely zero reports of any field testing from open source material of testing the round in combat. I have a hard time believing he ran a 6.8 in Iraq.

  • LilWolfy

    The most overlooked weapon profiles and the cartridges they fire are:

    * Squad-level Machineguns
    * DM and Semi Auto Sniper Systems

    Neither 5.56, nor 7.62 NATO are optimum for those roles.
    5.56 NATO is a very good performer for individual riflemen in most AORs.
    DM’s and Snipers would benefit from a high efficiency intermediate cartridge.
    LMG’s seem to have the most to gain from LSAT. The 6.5mm LSAT would smoke both 7.62 NATO and 7.62x54R PKM envelopes for reach and retained energy beyond 450-500m, with everything weighing less.

    For those that have humped 7.62 NATO, you know how restrictive it is to maneuver.

    • Brian M

      Solving MG and DMR problems is a bit thornier, because these are meant to be long range platforms and the MG has to beat cover and not get too hot. From militia stuff with 7.62x54R, I can absolutely concur on the weight aspect. As much as people love to shout ‘hit the gym’, there’s only so much you can train when just lugging your gear is guaranteed to put serious wear on the knees and back. Besides, if you can get in shape to carry 140 rounds of 7.62×51, then you’ve gotten in shape to carry 300 rounds of something SCHV. Now, there’s something called 7×43 Universal. Maybe you’ve heard of it? It looks pretty mean — hits hard, flies like crazy, and doesn’t kick too hard. I’m not sure about weight, however. Look up the website; I think you’ll like it.

  • cwolf

    If you look at the NSWC briefs and rqmts docs, the Mk 262 et al were designed to improve accuracy lot-to-lot and shot-to-shot plus increase lethality.

    Since the Lake City plant produces 1.6 B rds per year, the other consideration in ammunition design is the round has to be capable of high speed, high volume production.

    You’re correct. By definition, the infantry soldier (who does roughly 80% of the killing in today’s environment), wants to kill the enemy as his first priority.

    Feeding trolls attention is like feeding stray cats. It never stops.

  • LilWolfy

    You need to go to a 90gr VLD to get the type of BC needed for reaching out into the engagement distances we see that are typically covered by machineguns, snipers, and light mortars.

    In order to magazine-feed that in a compact profile like the AR15, you need a new case that is fatter, which will reduce the capacity per volume and make magazine pouches bulkier on the soldier’s load, pushing CofG farther away from the body’s core, and limiting mobility even more.

    This is why I’m still an advocate of a 2-caliber system, but that does away with 7.62 NATO. 7.62 NATO is the real drag on the system, not 5.56 NATO. 5.56 NATO allows maneuver and combat endurance (the ability to maintain volume of fire over time), in ways that changed dismounted warfare.

    The current 2-caliber system is limited by the weight and bulk of 7.62 NATO, the “heavy leg” of Infantry, when you actually analyze how a dismounted engagement unfolds.

    • Brian M

      What would you say about a switch to a 6mm alternative to 7.62? From looking at a lot of extant hunting cartridges, it would seem that 6mm, particularly 6.5mm rounds may be just the ticket, given that they can hit like a 30 cal with easily 85% or more of the energy (especially at long range due to good BC’s) but at less weight and recoil. I can’t really think of the weight savings right now, because I’d have to go run some calcs with numbers I can’t really recall, but IIRC, rounds like 6.5 Creedmoor can match 308 in a short action rifle with less recoil and weight. Even 243Win gets up to the 2k ft/lbs mark. And 6.5×47 LaPua is definitely up there while having a smaller case with less powder.

  • Monty01

    “In short, despite the resounding success of the SCHV concept, there was significant room for improvement.” This is a major understatement. As an ex-infantry officer with experience of both 7.62 x 51 mm and 5.56 x 45 mm, I would say the resounding success of the latter is entirely due to it being used more on ranges than in combat between its inception, in 1979 and Gulf War 2 / Afghanistan in 2002. One notable exception is Mogadishu in 1993, but after-action reports revealing serious issues with 5.56 x 45 mm terminal effectiveness were never made public. So, yes, indeed, there was significant scope for improvement. I tend to share your view that the concept of SCHV remains valid. A wholesale return to 7.62 x 51 mm would be a step back IMO. The real problem here, however, is not the size of the calibre, but the limitation imposed by the action length of 5.56 x 45 mm. If it were possible to adopt a longer and heavier 5.56 mm projectile (close to 80 or 90 grains) in a longer case (so that it had more power), then any objection to this calibre could be demonstrably overturned via a firing demonstration. Tony William’s tacit suggestion is, that if you’re going to make a longer projectile in a longer case, you might as well go who whole hog and increase the bullet diameter slightly. Why? Fundamentally, bullets kill in two ways: (1) A hit to the CNS – which is game over even in calibres as small as .22 Rimfire; and (2) through rapid loss of blood. Most people killed by small arms tend to die from the latter not the former – simply look at UK casualties in Afghanistan who were shot for evidence of this. This being the case, you want a projectile that maximises the speed of blood loss, especially in the event that the bullet doesn’t yaw in soft tissue. Larger, longer and heavier bullets tend to make a larger wound track that is likely to cause more tissue damage, especially when they hit bone. 5.56 mm can be equally as lethal as 7.62 mm, but not always. What you’re looking for is reliable incapacitation. i would say from my own experience that larger calibres incapacitate with increased certainty. Finally, there’s one more reason why Williams is right in his suggested approach. This is the increasing use of body armour. We need increased energy to penetrate the latest designs. I notice that SOCOM is conducting a test with .260 Remington this year. The ARDEC team are looking at 6.5 mm for LSAT. And the UK is conducting its own calibre study in support of the US Army’s one. This research should give us a definitive answer. Finally, when you package a 115 grain or 123 grain projectile in a polymer case, the weight growth of the resulting cartridge is 16 grams virus 12 grams. That’s a 25% increase. I am fascinated to see what the next generation offers. But what would you recommend, Nathaniel? An M855A2 EPR in 5.56 x 45, a .224 with a longer heavier and more aerodynamic bullet or something else?

    • As I said in the article, I think the subject needs careful thought and extensive groundwork-laying research and experimentation to come to the right answer. I haven’t done those things, so I can’t really back any one solution. I can only comment on possible solutions.

      Tony’s solution is one, but I’ve fought an uphill battle trying to get him to even think about concerns like adjusting his premises, or weight, or projectile design. His attitude initially, and even now to a lesser degree, was “I am right and it’s self-evident, and my theory needs no further scrutiny”. I have for some time tried to approach him with basic criticisms about his ideas, without backing a horse of my own, and he has not responded very well to that. I think now he sees me as just a party-pooper critic, honestly.

    • Brian M

      Monty, Nat, what would you say about this thing I cooked up:

      I propose a 7.62×39 case necked down to accept a .25 (6.35mm dia) bullet which weighs 100 grains. Pack it with 32gr of powder and you can achieve 3150fps and 2200ft/lbs from a 16″ barrel, all for ~7 lbs of recoil out of a carbine. It can be fired from any 7.62×39 platform with a simple change of barrel. To put it simply, something that can be used in the most common firearms family in the world, gets 7.62×51 NATO from a GPMG performance from a 16″ carbine barrel, has light recoil, and can be loaded using readily available brass and bullets.

      • Monty01

        This would definitely be interesting. The 7.62 x 39 mm case is an ideal start point and a 100 grain projectile would be sufficient to deliver acceptable terminal effectiveness beyond 300 metres. The issue is whether you could achieve the optimum level of performance within the 58 mm action length of 5.56 mm. Having looked at this in some detail, I don’t think you can. So you would probably need to extend the case to something like 45 mm. If you also used a long low-drag bullet, you would maintain energy over a longer distance, which would be a further point.

        Where i believe Nathaniel is coming from is that he maintains moving to a much larger calibre than 5.56 x 45 mm, i.e. above 6 mm, creates an unacceptable weight and recoil penalty. If i understand him correctly, then he’s right. A 100 grain 6 mm or 6.35 mm bullet could be just the answer. The overall length of the cartridge would be closer to 65 mm instead of 58 mm, so you would need a different weapon from the M4 platform. Overall, you would match 7.62 mm performance in a 5.56 mm package. That has to be a good thing.

        What do believe 100% is that 5.56 x 45 as currently configured has reached the limit of its development potential. There’s no more room in case for additional powder. Moreover, increased chamber pressure puts too much strain on the action. If you increase the length of the case and adopt a low-drag 5.56 mm bullet, you still need a longer action length to accommodate it. So you might as well optimise the calibre as well, by making it slightly larger. Textron is looking at 6.5 bullets for LSAT and the results seem extremely impressive. If the US insists on lead free projectiles, maybe 6.5 is better than 6 mm or 6.35 mm?

        I do wish someone with Nathaniel’s knowledge and common sense was leading development of military calibres in the USA. They wouldn’t go wrong by listening to him.

  • maodeedee

    6.5 Grendel 115-120 grains

  • Padmmegh Ambrela

    The concept of wounding an enemy so that his comrades are engaged in saving his life so now their are less enemy to fight is I consider far fetched. Of course this is useful for drawing out an enemy and ambushing them. But under combat conditions an individual or unit cannot do so on a regular basis. Beside an individual have to be a skilled marksman with knowledge of how to effectively wound (a wound which disables the ability of enemy to return fire without killing them) without reveling his or her position. Their are instances in history where soldiers where able to return fire even while being wounded and earned medals in their respective countries.
    Hague convention should be revised with respect to present and future combat scenarios, the whole case of humane way killing I found very medieval, except in those times soldiers pillaged after conquering. If you hate killing using expanding bullets or HE filled bullet this much why not stop war before happening. This ridiculous rules of old days prevent fielding of most effective weapons which might end war in less time instead of turning in a war of attrition. One can understand ban against chemical and biological weapons but against hollow point bullets or explosive filed bullets its ridiculous. Weapons should be precise effective killing tool not an indiscriminate one.

    • Zebra Dun

      Actually according to the statistics, more soldiers are wounded than killed.
      Doesn’t matter what the bullet is designed to do, wound or kill.
      Law of averages, I expect the Vietnam statistic of 50,000 rounds per one dead PAVN/VC is saying more soldiers are MISSED by bullets rather than wounded or killed no matter what the bullet is designed to do.
      The odds are if you are hit you have one in three of being killed, 50/50 of being wounded and a one thousand to one chance of being missed.
      Since more rounds are fired to keep the enemy ducking or gain fire superiority why design them to kill or even wound only?

      The M-16 and the 5.56 x 45 mm were designed to be easy to shoot and accurately HIT the enemy soldier whether they were killed, wounded or missed does not matter.

  • cwolf

    The somewhat larger issue in the dialogue is that any bullet/caliber is part of a large interactive system. Ph-Pk is a function of the total system, not just the bullet.

    For example, a soldier with an optical smart sight might be significantly more lethal than a soldier with iron sights. Lethality went up when new optical sights were issued.

    Or a soldier trained to hit distant targets or moving targets might be more lethal that one who is not. When the M16 was first fielded, the Army trained shoot center mass at 500 yards. Sort of incorrect since the bullet drops around 45″ at 500 yards.

    Or a friend had all his soldiers zero before every action. Kills went up. Sights, after all, get knocked out of alignment with rough handling. And, the NSWC developed the Mk262 partly because std Army ammo accuracy varied widely from lot-to-lot, even shot-to-shot.

    One service tested highly qualified KD shooters on moving targets. No hits.

    Or when the Army moved to qualifying in IBA in BCT with M16A2 rifles, qualification scores dropped (and the ammo bill went way up).

    Warfare scenarios have changed. In WWII, artillery was the big killer. In today’s wars, small arms are the big killer. Feedback suggests SDM are killing at far higher rates than non-SDM.

    Then you add in the aging rifle fleet. 1.6B rounds/year means lots of wear.

    So, bullets are only one variable. Therefore, given the multi-billion dollar system, new calibers are an uphill fight.

  • Mazryonh

    “The ideal round kills instantly with one shot, has no recoil, weighs
    nothing, has a perfect laser-trajectory, no muzzle flash, costs nothing,
    takes up little or no space, creates a suppressing hurricane of air and
    loud sonic boom around the target, yet is silent at the muzzle,
    penetrates all barriers at all ranges with no loss of effectiveness
    (while still having limited penetration for use in training facilities),
    and has no maximum range (while still having a maximum range within
    normal Army training ranges).”

    When you mention things like “no space, no ballistic drop, no recoil, no weight,” and “limited penetration for a training environment,” you know what fills most of those requirements? A man-portable Laser Rifle (actually a long gun, because it doesn’t use rifling, but who’s counting).

    You can’t dial back the energy a firearm cartridge delivers when it’s already loaded into a firearm, but you can in principle dial back the amount of energy a laser delivers with every shot, for training or even less-lethal use. And of course laser pulses don’t produce noticeable recoil or take up space in a “magazine” (actually a battery), though sound and suppressive ability when fired is an open discussion.

  • Dolphy

    Nat, I think 5.56×45 is pretty much developed as far as it can go unless we make some radical breakthroughs in propellants or projectiles. In terms of rounds, I think the mag well of the AR15 is the single biggest limiting factor in the way of working with new rounds.

    • Mazryonh

      I know I’d like to see some ballistic tests done with the 7x46mm UIAC. That caliber’s design wasn’t restrained by the dimensions of a STANAG AR-15 magazine.

  • Mazryonh

    As for “creates a suppressing hurricane of air and loud sonic boom around the target” but without actual impact anywhere near the target, I think something like that has been demonstrated (in film, anyway).

    There’s a French film called Sky Fighters (Les Chevaliers du Ciel in its native French) with a scene where a Mirage 2000 jet fighter exceeds the speed of sound a few meters from the ground, producing a massive sonic boom that does a spectacular job of “suppressing” everyone in the area. I guess that would be the closest you can get to a “hurricane-level” of sound, but then again, I don’t think anyone uses flashbang grenades to suppress people without collateral damage in non-law-enforcement situations.

  • georgesteele

    Hi – couple of typos, if you are still editing: there’s a farbled sentence or two up front that I’d be happy to help with editing, but the one that stood out was the caption under the 5th photo labeling the 7.62×39 as 7.62×29. I stopped checking at that point, in order to write this offer to help. I think this article is a valuable contribution, with lots of interesting information, so it is worth getting everything right. As an old tech editor, I’d be happy to do so if you’d like. Don’t misunderstand me – it’s useful information even with typos!

  • Zebra Dun

    Reality shows more targets are missed than wounded or killed.
    As in the Vietnam wars 50,000 rounds per enemy soldier killed.