Choices of a Higher Caliber: NATO, the US Army’s New Service Rifle, and Visions of Future Warfare

Beyond the Tactical Realm

While it is generally true that amateurs talk tactics and professionals talk logistics, ammunition calibers is a point where the two levels of conversation meet. The adoption of a new service rifle by a branch of the US military can appear to be a topic just for grunts and gun enthusiasts. However, even minute technical aspects can suddenly acquire great importance when they concern the largest branch of the world’s most powerful military. From a deeper analytical point of view, the adoption of a new individual service weapon that utilizes a new cartridge can have profound consequences at the tactical and even operational levels. In fact, an effective weapon can make the difference between life and death for the individual soldier on the battlefield and determine success or failure for small-level units to achieve their objectives. In a snowballing fashion, tactical units’ ineffectiveness can compound to make larger units also less effective, gradually making their effects heard at the operational and even strategic levels. Logistics directly impact strategy, and the switch to a different round by the US Army affects the interoperability among the branches for combined operations and among NATO partners for joint operations. Moreover, the adoption of the M7 rifle and its unique cartridge is also a window into the procurement system of the US Military and invites reflection on how conservatism and innovation – often at odds in military culture – need to balance each other out. Most importantly, conversations over battle rifle designs and calibers are actually debates over what warfare might look like in the future and how to tackle new challenges.

In May 2025, the US Army dropped the experimental “X” designator for its newly adopted service rifle in 6.8x51mm. This signaled one more step toward its adoption for the entire branch after its selection in April 2022 during the Next Generation Squad Weapons Program (NGSW). Started in 2017, the NGSW program represented yet another attempt by the US Army to replace the 5.56 NATO caliber M4A1 carbine – the individual rifle currently in widespread service with most units. This program, in turn, was part of the never-ending quest by the US Army to find the “best” armament capable of ensuring firepower, lethality, and allowing for the optimal organization of its units from fire-teams to armies. This constant pursuit of the perfect weaponry is the same impulse that led to the adoption of the M-1 rifle in 1936, the decision to retain a large-caliber rifle in 1957 with the M-14, and, in 1965, the selection of the smaller-caliber M16 rifle, of which the currently serving M4A1 carbine is a descendant. Some of these choices proved wise moves that made the US military a more lethal force. Others proved blunders that cost money and lives. The US Army and potentially the entire US military may make another similar decision that could have momentous consequences well beyond the tactical realm.

Future warfare seems to place less and less emphasis on ground infantry combat and more on long-distance power projection; confrontation in the air and sea domains; and drone and artillery warfare in the terrestrial domain. As a result, aerial, naval, air defense, armored, artillery, and cyber defense systems should obviously be on top of the list of priorities for governments and policy-makers. Nevertheless, individual ground combat will likely continue to retain its place in the foreseeable future, as evidenced in Ukraine. Therefore, quality equipment for ground troops should not be foregone, and alongside more advanced jets, drones, and ships, the US government and military have a responsibility to shape an effective procurement system to source it.

Capricious Choices

The adoption of a new service rifle and of an entirely new ammunition is relevant also from practical and operational standpoints. In fact, no other country within NATO uses the 6.8x51mm cartridge, making shared logistics potentially difficult in case of a common conflict. The whole point of the adoption of the 5.56x45mm as standard ammunition by NATO in 1969 and, before that, the 7.62x51mm in 1954, was precisely to ensure shared logistics among its partners. The move occurred despite British (as well as American) studies showing the greater effectiveness of “intermediate” cartridges between 6.5 and 7mm caliber. Moreover, NATO’s adoption of these rounds as a common cartridge was a consequence of the US’s unequal weight among nominally equal partners. To this day, the direction that the United States takes on military matters can drive those of all the other members of the alliance.

Ideas of what warfare would be like and realities of what it actually proved to be have long driven US military procurement. The adoption of the M-14 and its powerful 7.62 cartridge by the US military in 1957 occurred due to its unshakable faith in the continued importance of marksmanship at longer ranges over firepower rates in combat. However, new realities of combat at shorter ranges against high-capacity automatic weapons in intermediate caliber in Vietnam hit the United States when faced by guerrillas armed with the AK-47 family of rifles. Therefore, in 1964, the US military quickly replaced the M-14 in Vietnam with the M-16 rifle chambered in the small-caliber .223 Remington – much smaller than the intermediate 6.5-7mm caliber rounds. The adoption of the .223 round as the new standard US cartridge in 1963 was an admission that the 7.62 had not been the appropriate choice after all. Therefore, American procurement of small arms needs to be based on realistic appraisals of future combat and account for its impact on the rest of the NATO alliance.

A Deja Vu All Over Again

Since firearms can seldom be rechambered and adapted to new caliber cartridges, the adoption of a new round typically equals the need for a new weapon specifically designed to fire it. Therefore, evaluation, design, and production (sometimes in-country) of a new individual service weapon before its adoption and issuance can consume a significant portion of a country’s military budget. It is for this reason that the switch to a smaller round in 1963 by the United States received a great deal of criticism from several NATO partners that had just adopted battle rifles in 7.62, with the 5.56 ultimately being officially adopted only in 1980.

Today, in a replay of the events of the 1960s, the adoption of the 6.8x51mm as the cartridge for the primary service rifle happens just a handful of years after some of NATO partners have adopted new or updated rifles based on the AR-15 platform in 5.56 – most notably Germany, France, and, soon, the United Kingdom. The M7 rifle and its unique caliber raised eyebrows not only from international partners but also from within the American military, since no one other than the US Army employs them. While the issue may be less relevant for branches less involved in ground combat, like the Navy and the Air Force, it greatly affects the Marine Corps, which selected the M27 Infantry Automatic Rifle (IAR) in 5.56 to equip most of its infantry in 2017. While interoperability and logistical issues between international partners may be detrimental, they can be extremely problematic among branches of the same military in the context of joint operations.

What Kind of Future Warfare?

At their core, ammunition choices relate to the type of warfare that a military plans on fighting. In turn, such discussions are tightly connected to historical trends of warfare. Even before World War I, some countries – including Italy and Japan – realized that the round of the standard infantry rifles was unnecessarily oversized and saw the potential in smaller cartridges to provide more ammunition and firepower with the same lethality. In the interwar era, many militaries saw the potential of repeating and semi-automatic rifles, and just prior to World War II, the US military adopted the M-1 rifle, which went on to be one of the most successful rifle designs in history. The experience of World War I showed even more clearly that soldiers on the battlefield required firepower and mobility and that intermediate caliber rounds could ensure both. It was during the interwar years that the smaller .276 (7x51mm) Pedersen cartridge gained favor in the United States. The United States, however, retained the powerful .30-06 in part due to financial considerations and in part to ensure ammunition interoperability between rifles and machine guns at the small unit level. Behind this choice, however, was most of all the continued importance placed by traditional doctrine on marksmanship for an idealized open warfare. In other words, in the mid-1930s, the M-1 rifle seemed to provide exactly the greater firepower the US military needed, while the .30-06 was the powerful cartridge it thought was necessary.

In part, the adoption of the new 6.8x51mm round today comes as the answer to complaints by US military personnel in Iraq and Afghanistan that the 5.56 NATO of their AR-15 platforms lacked stopping power. Recent studies confirmed previous findings that intermediate cartridges between 6.5 and 7mm and larger than 5.56 NATO provide optimal performance for lethality. Other complaints – although not widely shared by veterans of Afghanistan and Iraq – were also that the 5.56 NATO rounds lacked the range sometimes required in medium and long-range engagements there. It is notable that the 6.8x51mm cartridge resembles the Italian and Japanese cartridges of the World War II era and before, long identified as the ideal caliber to ensure performance and lethality at both close- and mid-ranges. In any case, post-WWII studies evidenced that the ranges at which most soldiers could see enemy combatants standing up were less than 300 yards for seventy percent of the time, and less than 700 yards for ninety percent of the time, meaning that only in ten percent of cases could soldiers see standing human bodies at distances greater than 700 yards. In other words, soldiers typically would be unable to even spot enemy soldiers beyond 700 yards, let alone successfully shoot at them.

Nevertheless, the implementation of an optical sight – an NGSW requirement from the start – can greatly correct the limitations of human eyesight and extend the ranges of feasible engagements. Matthew Ford, associate professor at the Swedish Defence University, points out in a recent article that this comes at a significant cost and weight gain for the individual load carried by a soldier, something very problematic when combined with a larger army of draftees needed in case of a peer-to-peer conflict – exactly what the 6.8x51mm round is designed for. Additionally, Ford highlights that its higher penetrative power of the new round might not be useful in fighting enemy insurgents not equipped with ballistic protection. However, the assumption that future conflicts will continue to be low-intensity wars and insurgencies may not prove true. Surely, Ford accurately highlights the stress under which the British Ministry of Defence, for one, is for other procurement and supply issues. The selection of a new caliber that would demand the rehauling of the entire ammunition production and supply line (not to mention the adoption or design of an entirely new weapon system) would be enormously problematic for it, as well as for other NATO militaries. This is, however, a self-inflicted wound as a result of historically inadequate defense budgets and neglect of the defense industry by many NATO countries. In fact, small arms and ammunition production do not seem to be points of concern for the United States as they are for the UK and other allies.

International security expert Alan Orr has forcefully argued that the Army’s shift to the 6.8x51mm round represents a move to the other end of the spectrum from the 5.56 NATO and the scenario of counterinsurgency. Considering that the 6.8x51mm is precisely the type of intermediate cartridge that American, British, and European militaries and firearms experts have been asking for since the 1930s as the most appropriate for most types of engagements, Orr surely must have been thinking of the full-size 7.62 NATO round that was adopted instead. Writing in 2022, he observed that Russia has not issued standard body armor to its soldiers in Ukraine, which is only a partial truth that tells us nothing about the kits issued to the Chinese military.

A Circuitous Procurement Process

The development and adoption of the M7 after several previous attempts with promising prototypes (the XM8 and the SCAR) that eventually did not replace the AR-15 platform in US Army service occurred during years of almost frenetic adoption of other equipment, including the SIG Sauer M-17 service pistol in 2017, the Barrett MK 22 Precision Sniper Rifle in 2021, and, very recently, the M250 Squad Automatic Weapon (also by SIG) in 2025. This flurry of adoptions comes after decades of sluggish research, development, and evaluation programs characterized by red-tape-induced cost-overruns and timelines so stretched out that the technologies being developed were outdated before they could be adopted. This occurred precisely because simplified acquisition programs and streamlined research processes were activated to avoid these overly complicated and lengthy routes. So far – as in the case of the new sidearm, sniper rifle, and, it seems, the freshly adopted SAW – this approach has paid off with weapons that are an improvement over their predecessor. Nevertheless, the checks and mandated waiting periods that mark research, development, and evaluation programs are intended to prevent the rushed adoption of equipment liable to cost tremendous amounts of money for little advantage, at best, or negative consequences, at worst.

The jury is still out on the M7 rifle. However, the concerns that several analysts and firearms experts have expressed over the months have recently been revived just last May with the publication of a scathing report on the M7 rifle by Braden Trent, a US Army infantry officer currently attending the Marine Corps University’s Expeditionary Warfare School. More than the rifle’s technical issues, evidenced in Trent’s report – typical of any weapon still under development – disturbing is the Army Captain’s criticism that the combat philosophy behind the rifle and its cartridge is outdated. Trent maintains that expectations that US personnel will be facing enemy combatants wearing ballistic protection have been disproven in Ukraine, and that experiences there did not show the need for a more powerful round for engagements at longer range. He also suggested that simple measures like the adoption of armor-piercing 5.56 NATO rounds could simply solve the difficulty of penetrating enemy ballistic protections if they showed up, although they would not increase the range. Additionally, the round proposed, specifically, called M955 Armor Piercing, is several tens, if not hundreds, of times more expensive than the standard 5.56 M855A1 Enhanced Performance Round because it contains a tungsten carbide core, the supply of which could be problematic, considering that China is its largest supplier in the world. Interviews with US Army personnel currently testing the rifle in Trent’s report also indicated that the heavier weight of the rifle, moreover, negatively impacts shooters’ performance at both shorter and closer ranges. Although Sig Sauer seems to have addressed the weight issue by reducing the weight of the rifle by nearly a pound in October 2025, this does not increase the number of 6.8x51mm ammo soldiers will be able to carry. Soldiers in Trent’s report felt limited in the firepower they were able to provide with an ammunition combat load of just 140 rounds compared to the 210 5.56 NATO rounds they could carry if armed with the current M4A1 carbine. It cannot be denied that a more limited ammunition can negatively impact small-unit effectiveness by making it difficult to provide suppressive fire, the pillar of modern fire & maneuver small unit tactics.

Reading the Tea Leaves of Future Warfare

Like in 1936, 1957, and 1965, the US Army is at a crossroads with a question that is perhaps technical in nature but reflective of wider considerations of the type of warfare it expects to fight. The answers to this question will affect the other service branches, as well as America’s allies. Much like when the US adopted the M-1 and the M-16, the choice it will make may prove to be the right one. However, it may also turn out to be the wrong choice, as it was in the case of the M-14.

No matter what, it is absolutely crucial to ensure that the research, development, and evaluation process for the M-7 rifle, while not being hampered by red tape, is also as careful and transparent as it could possibly be. In terms of what kind of weapon will be needed, as with any armament, obtaining the perfect rifle and cartridge for all types of combat is not possible. The search for a weapon that could somewhat perform in any situation could lead to producing a weapon that is truly satisfactory in none. As a result, the best bet is to prepare for the worst-case battle scenario and select weapons that can best deal with it, as well as, if needed, with less likely different ones. Sticking with the AR-15 platform and the 5.56 NATO cartridge would mean continuing to embrace a specific end of the spectrum of warfare of low-intensity conflict and counterinsurgency. There is something to be said about gearing up for the conflicts one expects to fight rather than the ones just fought, even if the process is sometimes more akin to reading tea leaves than making surely accurate predictions. According to most analysts, the tea leaves are pointing at conflicts with near-peers – most likely Russia and China – whose soldiers could be wearing ballistic protection in the worst-case scenario, regardless of whether they currently are or not. Additionally, engagements occurring at medium ranges between 300 and 500 yards, already frequent in the years of counter-insurgency, are, if anything, more likely to take place in the case of peer-to-peer conflict. The M7 rifle (paired with the M250 SAW chambered in the same cartridge), equipped with fire control optical systems that extend the limitations of the human eye and assist in aim and firing an intermediate 6.8x51mm round capable of reaching and defeating ballistic protection at mid-ranges, seems the best bet for such near-peer wars. The American All-Volunteer Force is not a conscript force but rather a professional fighting force that the American public must be willing to equip with top-of-the-line gear to increase their effectiveness, including expensive optical systems for their rifles. While a draft and the recruitment of a conscript force might be necessary in an all-out fight against an enemy superpower, the current force – if necessary, through additional training – is capable of handling more complicated, expensive, delicate weapons as long as the advantages are unmistakably there.

In the end, the point of the matter is to try to clearly assess the battlefield challenges of the future and address them. If there are reasons to dismiss the M7 rifle and the general concept of a truly intermediate cartridge in order to tackle the expected conflicts of the future, these reasons should be sound and logically argued. Looking exclusively at the recent past will not cut it, nor will pretending that the current equipment is “just fine.” Unwillingness to sort out the issues that arise while pursuing technical innovation is likewise not acceptable: the risks that derive from unpreparedness are too high to allow it. Analysts and commanders must realize that continuous refusal to leave the known comfort zone of utilizing current equipment can be as much a recipe for disaster as jumping on the newest, coolest gear. In fact, while the attractiveness of new tech can also be risky, excessive conservativism can bring about the same dangers. Historically speaking, conservatism has damaged militaries – the US armed forces in particular – more than attempts at reform, especially in the field of firearms, as in the case of the .30-06 M-1 and the 7.62 M-14. This endless wait for revolutionary rather than simply evolutionary technology has stoked progress time and again, while adversaries have seized the advantage. Military leaders at all levels must strike a balance between innovation and caution, even when dealing with issues that may only seemingly be of a technical nature, because in fact service members’ lives often depend on it and because their implications can be far-reaching.