Throughout history, the clashes of armies have been settled at the close range and vicious pace of the infantry firefight. From the mountains of Korea to the jungles of Vietnam, across the far-flung Falklands to the cities of Iraq – even in a nuclear age the adage remains true that it always comes down to the infantryman and his rifle. Though their prime of place has long been eclipsed by artillery, tanks, and aircraft, the militaries of the world still devote a great deal of effort towards maintaining and improving their infantry forces. It is thus unsurprising that a modern trend exists hoping to solve through technology the perceived weaknesses of the branch. Where the tank has questions of defeating ATGMs and achieving yet better armor penetration, and aircraft have questions of stealth and payload, the task to which today’s designers have devoted their labors is one of range. The question which so many have asked, and whose proffered answers we shall here discuss, is the following – “How can the range to which unsupported infantry effectively detect, target, hit and kill enemy infantry forces be increased, assuming no radical shift in the level of proficiency or of tactics.”
This question is perhaps as old as ranged infantry themselves. The adoption of the rifled musket and later the Minnie ball, the creation of smokeless powder, eventually to be paired with the Spitzer bullets so common today – all have been answers in their day to this question. Even the modern divergences from this mold, the adoption of intermediate calibers and later of small caliber high velocity designs, seek to improve the effective range of the thing before them. (Pistol caliber automatics and early intermediates, respectively). Though perhaps dormant for a time, the modern mass issuing of magnified optics and continuing US commitment to the mountains of Afghanistan has done much to reawaken this trend. Encapsulated in modern notions such as “overmatch”, the desire to “retake the infantry half kilometer” (to cite a specific advocation) have spawned a number of proposals, and it is these which this piece hopes to discuss at length.
The article shall proceed as follows. Firstly, key considerations and constraints will be enumerated. Second, we shall examine proposals relating to the individual infantryman’s weapon. Third, we shall examine those relating to the supporting weapons – light and medium machine guns, alongside precision weapons. The remainder of the discussion will be in a follow-on article, and will discuss explosive weapons at the infantry’s disposal, before laying out a final analysis and what the author perceives to be an ideal solution. This solution will by no means be authoritative or definitive – the author is little more than a layman. It is merely hoped that this article will lead to more knowledgeable and fruitful conversation amongst enthusiasts, laymen, and perhaps even a few professionals who deign to give it credence. With this established, and with the author’s long-winded nature surely straining patience, let us begin.
We turn now briefly to constraints. Our first and most pressing constraint has remained unchanged since Roman sandals trod the far corners of the discovered world – weight. From food to water to weapons to ammo, the material of war must be borne on the infantry’s backs. This capacity has been pushed almost to it’s breaking point – a recent GAO survey reported that the average combat load of a US Infantry Soldier was 120lb/54kg. Therefore, any proposed change must be carefully measured against its increase in weight. Equally important are considerations of training and target identification – quite simply, making accurate hits on targets which do not wish to be seen becomes very very difficult as ranges increase, especially when factors such as stress and exhaustion are taken into account. Thus, to achieve our goals, we must pair our “hardware” solutions with “software” solutions of equal if not greater scope and scale. Individual marksmanship in realistic conditions and at extended distances must be adopted and practiced regularly, in addition to the expenses of better scopes, more accurate ammunition, and better training facilities. Lastly, it would behoove one not to neglect the advantages inherent in modern designs – modern 5.56 is extremely lethal even from carbine length barrels past 300m, and it offers excellent controllability and mild recoil. These characteristics become increasingly relevant as the range closes, and the close-quarters excellence of 5.56 should not be quickly discounted.
Now that we have identified key constraints upon our solutions, let us briefly examine the format upon which they will be applied, and the solutions which have already been adopted. Though our solutions would ideally be applicable for multiple militaries, we shall examine them here by applying them to the US Army’s rifle platoons, of which there are 3 variations. The intimate cooperation between the dismounts and the Bradleys of the rifle platoon in an Armored Brigade Combat Team would seem to render their discussion here moot. This leaves us with the rifle platoons within the Stryker BCT and the Infantry BCT, the organizations of which have been presented below.
Both platoons consist of a headquarters element, a weapons squad with 2 machine guns, and three rifle squads, each consisting of two fireteams based around an light machine gun. They differ in that the IBCT rifle platoon contains two Javelins in its weapons squad, whereas each rifle squad in the SBCT carries a Javelin in its vehicle to be carried as necessary. With the exception of the 7.62×51 M240s in the weapon squads and DMR-type weapons issued at the Commander’s discretion, all weapons are chambered in 5.56×45, and both 7.62 and 5.56 weapons fire an Enhanced Performance Round, a family of new designs that increase penetration and terminal ballistics.
An interjection regarding units and conventions – velocities will universally be given in feet per second, however, the ballistic calculator the author has easy access to is in units of yards. Units given to the reader will be in terms of meters – this is not a mistake, conversions have been undertaken behind-the-scenes as necessary. Effective range has been taken here to be the range to which a bullet remains outside of the supersonic – above 75fps faster than Mach 1, due to the unpredictable effects of crossing the sound barrier. Though hits obviously do occur beyond this, they become very difficult to achieve. Regarding lethality, though the link between “fragmentation velocity” (the velocity below which a round is unlikely to fragment and or expand) and lethal terminal effects is an imperfect one, it is suggestive of a lethal range for the projectiles, and will be presented with the understanding that this is an imperfect measure. G1 and G7 represent varying formulas for ballistic coefficients, which can be roughly understood as measurements of how well a bullet retains velocity while travelling through the air.
Of the Soldiers in our infantry platoon, the vast majority are armed with a 5.56 carbine. Though the advent of new 5.56 loadings such as Mk318 and M855A1 and the almost-universal adoption of magnified optics have done much to increase these carbines’ range, this is the first place to which many solutions for increasing range are applied, due to the preponderance and prestige of the individual’s rifle. We shall examine these solutions in detail here.
(6.5 Grendel compared to civilian variants of 7.62 and 5.56)
A number of calibers have been proposed in the past decade or more to fix perceived issues with the 5.56 caliber rifle, most of which can be retrofitted into existing rifles merely by changing out the bolt and barrel. Some, such as .300 BLK or 6.8, have focused primarily on increasing effectiveness and penetration at close range, or when fired out of short barreled carbines. 6.5 Grendel, on the other hand, is an adaptation of bench-rest precision calibers into the AR-15 platform. In this, it is a truly exceptional caliber, featuring many rounds with excellent ballistic coefficients and superb long-range performance, as well as impressive accuracy from the very beginning. Thus, to many, if offers a good retrofit method to increase the long-range capacity of the Soldiers’ rifles.
One of the great benefits of the 6.5 caliber used in 6.5 Grendel is it’s myriad selection of different bullet types. However, as it currently stands, this bullet selection is oriented towards civilian uses of hunting and precision shooting. While this leads to excellent ballistics and good performance against soft tissue, modern militaries often highly value penetration of barriers as well. Thus, in creating a 6.5 Grendel loading to compete with M855A1, we will use a hypothetical 6.5 caliber EPR bullet, similar to the one shown below.
(Cross section of M855A1 compared to earlier SS109 – note 3 part construction of exposed steel penetrator, copper slug, and jacket, leading to excellent penetration and fragmentation)
In this, we are fortunate to be able to exploit the sterling work of Nathaniel F at TFB; in his “Romulan, or Vulcan?” article, he sketches out a variety of new EPR bullet designs, one of which is of 6.5 diameter. Using this 108gr bullet, the known velocity of a 107gr 6.5 Grendel round in a 16″ barrel, and the rule of thumb that 25 fps of velocity is lost per inch of barrel length, we are able to determine the performance of a 14.5″ barrel carbine chambered in our 6.5 Grendel EPR cartridge. A comparison between this hypothetical round and the known performance of an M4A1 firing M855A1 has been reproduced below.
In defense of this 6.5 Grendel EPR, it should be noted that it goes from having 5/4th the energy of 5.56 at the muzzle to double 5.56’s energy by 550m, as well as an additional 125m of supersonic range and easier compensation of wind factors due to it’s heavier weight. However, the trajectories of the two rounds are almost identical, and a difference in fragmentation range – while slight – exists in the favor of M855A1; therefore it is reasonable to assert that a 6.5 Grendel carbine would not benefit us in our attempts to increase the effective range of fires. A natural counterargument is that this comparison is foolish, as 6.5 Grendel is intended to be a precision round fired from longer barrels, and that if we intend to increase effective range retaining the 14.5″ barrel of our carbine is a senseless move. This argument will be examined at length in a later section; for now we shall devote our efforts solely to the 14.5″ carbine. An additional examination of the trajectory at ranges within 300m has been reproduced below, including a 90gr civilian loading for reference.
We see in this chart the first of many potential issues with adopting a 6.5 Grendel carbine. For both our 90gr commercial loading and the hypothetical EPR loading, 6.5 increases the difficulty needed to make a hit within 300m. Whilst counter-intuitive, the slower initial velocity means that a round which is more potent at longer range has a greater amount of drop at close range, reducing the ability to “point and shoot” granted by high velocity designs. This is in addition to the increased recoil of a heavier round disrupting the the shooter to a greater degree, and the reduced (albeit to a small degree) magazine capacity. Thus, shot-for-shot, it is likely that a 6.5 Grendel carbine would gain less hits than one in 5.56. Moreover, not only is the ability for each shot to gain a hit reduced, but the number of shots is reduced due to the increase of weight per shot. For the nominal fighting load of 210 rounds of 5.56 for the individual, roughly 150 rounds of our EPR 6.5 Grendel can be carried. Whether these costs are worth an additional supersonic range of 125m and greater ease dealing with wind is left to the reader; however, it’s should be obvious that the other views it to be of dubious validity, especially for the fireteam’s carbines.
(FN SCAR-17 and HK-417 variants)
The most natural response to a need for longer range firepower is to revert to heavier, rifle-caliber weapons such as the AR-10, M14, FAL, and G3 series. These weapons would, it is often assumed, be relatively cheap and easy to (re)issue, and provide the individual shooter with a longer-ranged weapon than the intermediate caliber 5.56 carbines in use.
As shown by the US Army’s ill-fated ICSR program, existing stocks of M14 rifles at least 53 years old are considered insufficient to meet the need of a potential general-issue 7.62×51 weapon, partially due to their age, and partially due to the less accurate nature of older designs. It is reasonable to assume this trend will be the same for other militaries, and thus we will thus base our potential rifles on existing or proposed weapons, such as the G28, the M110/M110A1, and the stillborn ICSR. The 8.4lb weight and 16″ barrel of the newly adopted M110A1 would appear to be a good starting point, especially since this 16″ barrel was present in published ICSR requirements. This weapon shall serve as our carbine, and a theoretically longer-length DMR type weapon will be presented later. Ballistics charts comparing these weapons to existing 5.56 types have been reproduced below.
The performance gains of the 7.62 round become evident largely after 500m, with the 7.62 carbine having around 100m further supersonic range than the M4A1’s 650m. This is in addition to compensation for wind being far easier, a particularly troublesome task as distance increases. A comparison of “fragmentation range”, the range out to which the projectile retains enough velocity to reliably fragment, is less severe; the 7.62 carbine having a further 70m over the M4A1’s 350m. (Though, admittedly, the understanding of M855A1’s fragmentation velocity is incomplete, and it has been anecdotally reported to fragment out to 400m.)
Unfortunately, however, the factors which apply to a 6.5 Grendel carbine apply more so to a 7.62 carbine. The issues of weight, capacity and recoil are all the more severe, to the point where the author views the suggestion as infeasible. Losing either 100 rounds of capacity or gaining ~6 pounds of load in return for a pound-heavier weapon which recoils more and contains fewer rounds per magazine appears unacceptable. Further, to truly leverage the long-range performance of a rifle caliber such as 7.62 NATO would require a distance-oriented weapon, itself unsuited to the close-range nature of many infantry firefights. As with a 6.5 Grendel precision weapon, this will be discussed at length later.
(Brass and Polymer cased .264 USA besides 5.56 and .308, credit to Nicholas Drummond)
Given our discussion of civilian cartridges, it should come as no surprise that the US Military has produced its own answer to increasing the infantry’s range without the weight penalties of a full-sized rifle round. One such round, put forth by the Army Marksmanship Unit, is the .264 USA. Greater in diameter and length than 6.5 Grendel, the .264 USA leverages low-drag bullets to increase effective range, even compared to 7.62 NATO. In terms of it’s size and weight, it bears more than a passing resemblance to earlier types such as .280 British, and is but the latest in a series of “general purpose cartridges” attempting to unify the 5.56 and 7.62 weapons with a round that improves both. Additionally, versions of the cartridge have been developed which use a lighter polymer case to further offset concerns of weight. In general, this round is paired with the “AR-12″, a 16.7” barreled AR-15 derivative of weight only slightly higher than an M4A1 carbine. A comparison of performance is made below, between a low-drag EPR .264 round, M855A1, and the ICSR carbine.
We can see evident here a modest, but appreciable level of performance over the 7.62 weapon, and a much greater increase relative to 5.56. An additional 200m of supersonic distance has been gained over the 7.62 weapon, and a full 330m over the 5.56. Fragmentation range is a less-drastic increase, with a respective boon of 100 and 160m. That this is offered by a conventional round lighter than 7.62 is doubtless impressive.
These advantages are not without cost – though weight is noticeably less than 7.62, especially with polymer cases, issues of capacity and weight will still burden this cartridge relative to 5.56. More pressing to the author’s perspective is the increased recoil of such a type – the higher kinetic energy of such round means the shooter’s sight picture will be more rapidly disrupted, and their rate of fire with effective aimed shots will be reduced. In this the smaller size of the .264 USA round vs 7.62 is a double edged sword, as this means a .264 USA weapon will be smaller and therefore lighter for a similar amount of energy being released when fired, exacerbating felt recoil. However, as before, the author leaves it to the reader to decide the worth of this proposal, and the fact that the author views it as being of dubious worth is doubtless clear.
As a final note – the idea that adopting a new round will be able to unify the ammunition used by the squad’s machine guns and carbines smacks of fool’s gold. Not only do these weapons typically fire specialized versions of each cartridge, the ammunition is provided for the weapon segregated from the factory. From the very moment the US Military takes ownership of it, ammunition intended for machinegun use is belted, whereas that for carbines is loose or on clips. While it would doubtless offer some logistic benefit, from the perspective of the rifle platoon, even when ostensibly using the same cartridge ammunition is not interchangeable. Thus, sacrificing the specialization present in maintaining a distinct machine gun cartridge and a carbine cartridge would garner little practical benefit at the cost of decreasing the suitability of either cartridges.
(Cross sectioned Mk262)
Stepping beyond the potential of rechambering the squad’s rifles, one possibility to gain extended range is the broader, or even universal use of heavier “match” bullets such as Mk262. A 77gr bullet adapted from civilian target loadings, the excellent construction of Mk262’s bullet means it retains its velocity better than typical ball rounds, performing superior to normal 5.56 at distances in excess of 700m. Further, it is loaded to extremely high standards (as denoted by “match”) leading to extremely impressive accuracy. It’s performance benefits have been demonstrated elsewhere, being able to perform admirably compared to calibers far larger than 5.56; however, as an example – Mk262 has 20% less wind call at 700m compared to M855A1 when fired from an M4 pattern carbine. This equates to far easier hits at range, making long-distance fire more achievable. Additionally, there is a great deal of benefit in retaining a 5.56 cartridge, as Mk262’s excellent long range performance is mated to the light weight of 5.56 and the pre-existing stock of magazines and spares. In this way, Mk262 offers an excellent method of extending the infantry platoon’s range without a major reinvestment in terms of equipment or hardware.
The benefits of Mk262 are not without drawbacks, unfortunately. Firstly it is an expensive round; it was evaluated during the replacement program for M855 and was determined to be four times as expensive, far beyond program goals. (FY2017 acquisition suggests a price twice that of M855A1, the current general purpose ball round). That New Zealand has standardized on Mk262 means this problem is not insurmountable, but it is a potential issue. Moreover, the increased ballistic performance of the Mk262 is a double edged sword – it’s ballistic trajectory is very different from common 62gr rounds, meaning optics with a Ballistic Drop Compensator such as the ACOG series would need replacing. (Admittedly, such a process could be done via retrofit of existing optics or as a procurement of superior optics.) Lastly, the performance is not a free lunch – Mk262 and other 77gr bullets of similar construction have poor barrier penetration compared to standard 5.56 rounds, and often exhibit worse terminal ballistics against personnel at close range. (Though, notably, superior terminal ballistics than legacy types such as SS109.)
(Limited overview of the development of the AR-15 family in US military service.)
A growing trend across western militaries, already largely complete within the US military, is replacing full length rifles with shorter barreled carbines, a transition generally from barrels of 20″ to ones of 14.5″. While this has no noticeable effect on precision (especially given the standards to which military ammunition and barrels are held), it noticeably reduces the velocity of the round, leading to greater drop and potentially lessened terminal effects. Using the two discussed 5.56 rounds, M855A1 and Mk262, the drop when fired from a 14.5″ and 20″ barrel has been reproduced below, indicative of the ease of hitting a target at range.
In terms of effective range by measure of distance before going transonic (75fps faster than the speed of sound, typically), Mk262 gains 110m supersonic range by switching from a 14.5″ to 20″ barrel, likewise a gain of 54m supersonic range for M855A1. In terms of lethality, M855A1 is capable of fragmenting 50m farther when fired from a 20″ barrel versus one of 14.5″, likewise a full 100m farther for Mk262.
In return for this performance, the expenses paid are in increased weight for the same profile of barrel, and increased overall length of the weapon. While the effect of a weapon’s length is difficult to quantify, the weights of the M4 Carbine and M16A4 with similar profile barrel are 6.4 vs 7.7 pounds (the US Army’s heavier profiled M4A1 weights 6.74lbs).
In the author’s estimation, the increased length and weight for marginal benefits at range (indeed, ones which show themselves primarily at ranges beyond the 300m to which US Army Soldiers are trained to fire) are not worthwhile for the majority of the rifle platoon; however, it becomes evident that any DMR/precision rifle concept to be adopted would benefit from a longer barrel. One potential outgrowth of this, should the IAR concept gain further traction, is equipping fireteam-level weapons such as the M27 with barrels longer than their current 16″ length. This would provide the fireteam with a longer ranged supporting weapon for a marginal increase in weight, while retaining the light and compact nature of the majority of their weapons.
We end here our discussion of the individual Soldier’s rifle, and turn to the greatest producer of casualties on the battlefield – the machine gun. We will examine both squad and platoon level automatic weapons, and well as briefly discuss potential options to extend the range of “DMR” or precision fires.
Doctrinally, the infantry platoon contains at present two M240 machine guns, as well the ever-present suggestion of adding 7.62 NATO Designated Marksmen’s Rifles of some sort. However, whilst a NATO standard, 7.62×51 was originally designed to match the performance of a 80yr old round, M2 Ball. It is safe to say that modern ballistic designs exist that can meet or exceed these specifications in significant ways. The one we will turn to today is 6.5 CM, a very ballistically efficient cartridge descended from .308 Winchester. In return for a slightly smaller diameter bullet, the 6.5 CM round retains velocity and energy far better than even specialized long range .308 rounds.
Comparison of 6.5 CM and 7.62 NATO chambered M240; the superiority of the 6.5 CM should be readily apparently. The 7.62 M80A1 round goes supersonic past 845m, whereas the 6.5 CM round goes supersonic around 1500m. It is worth noting in 7.62’s defense that the M80A1 ball is a construction which values penetration over energy retention, a more straightforward comparison is below.
While no slouch, the precision-oriented M118 LR round still goes subsonic around 900m, versus the 1500m of 6.5 CM. (Ballistic Coefficients and velocities are of a Hornady ELD Match round, confirmed by USASOC testing.) What is more, 6.5 CM is slightly lighter than 7.62×51. Albeit not an earth shattering aspect, this at the least guarantees that the added performance comes at a weight decrease to the Soldier, rather than a weight increase.
Unfortunately, the major downside to 6.5 CM as it currently stands is barrel life of the weapon – a brand new barrel can be destroyed in as few as 7000 rounds fired. While potentially acceptable for a precision rifle, it poses a major difficulty for the extended firing cycles of machine guns, which could see 20,000 rounds fired before replacement of the barrel. (A separate task from changing the barrel during firing.) Even assuming a more generous round count of 10,000 before replacement still represents a major decrease in lifespan. Thus, in addition to the cost and complication of a switch from .308 to 6.5 CM MGs as a whole, an additional logistical penalty of barrels would be incurred which may prove insurmountable.
As discussed previously, the .264 USA round offers performance advantages over 7.62 NATO in the realm of the infantry carbine, due to its slightly higher velocity and it’s improved ballistic properties. In the same manner, it could offer performance advantages over the incumbent 7.62 chambering of the platoon’s medium machine guns, without the reduction in barrel life of 6.5 CM. Using the low-drag EPR projectile from earlier produces the comparison below.
We see a similar level of performance increase as earlier represented here. Adopting the .264 USA cartridge using a 108gr EPR projectile merits us a further 230m supersonic range and 120m further fragmentation range compared to M80A1 ball ammunition. Especially if paired with a polymer cased ammunition, this offers a reasonable level of performance increase without the higher logistical penalty of 6.5 CM.
An option which has been adopted by the USMC, the Australian Army, and several others is that of the fireteam level IAR/DMR type weapon. These weapons trade the open bolt and greater sustained fire of a belt fed weapons such as the M249 for the higher precision, lighter weight, and better close quarters ability of a closed bolt weapon such as the M27. One possibility that this leads us to is replacing the SAW of one fireteam with an IAR/DMR pattern weapon. Drawing from earlier options considered previously, we compare the performance of a 5.56, 6.5 Grendel, and 7.62 NATO DMR type weapon. This has been represented below.
In this case, the comparison is between the 18″ barreled Mk12 SPR, an 18″ 6.5 Grendel weapon, and the 20″ M110, all firing specialized long-distance ammunition. We see that a relatively close ballistic match up to 650m, beyond which the 7.62 weapon clearly outperforms its stablemates. However, though it should be evident, even when trajectories are closely matched, the heavier rounds will require less compensation due to wind. As a note of compliment to the 6.5 Grendel, it’s supersonic range of 890m is only 10m less than that of M118LR, and 180m further than that of Mk262. It should be noted that this is using a 5.56 weapon with a longer barrel than the USMC-issued M27; this is a conceit to the pursuit of longer range, and not one outside the real of possibility for known weapons. As should be evident, the M249 itself has been excluded here. This is due to the open-bolt nature of the weapon making aimed precision fire very difficult, especially as distance increases.
A major downside to the adoption of a IAR/DMR type weapon in one fireteam is that the squad’s base of fire, their machine guns, is cut in half. This is largely viewed as unacceptable from a tactical perspective, and that is a worthwhile criticism. It is certainly relevant to point out that the Marines operate in squads of three fireteams, typically carrying M249s and IARs in a 1:2 ratio. However, the author will leave it to the reader (and the second article) to mull over the implementation of these ideas. For now, it will suffice to describe how these various IAR/DMR weapons compare against one another.
This is the end of our consideration of “conventional” brass-cased replacements. We now turn towards more radical developments, and to the family of Polymer Cased Telescoped rounds.
(Polymer Cased Telescoped weapon, developed by the LSAT/CTSAS program)
Ever since the adoption of the 8mm Lebel in 1886, the military shoulder weapon has fired a cartridge consisting of a brass case, smokeless powder, and metallic projectile. In the intervening 130 years, the militaries of the world have all but reached the developmental limit of the design. As matters stand, the nexus of development is focused on replacing the cartridge’s brass case to increase performance and reduce weight. Though a number of such programs exist, including most notably the German G11 project, the focus of our attention here is the US Military’s LSAT/CTSAS program.
Beginning development in 2003, the current CTSAS program had it’s spark in studies of Soldier’s load, and in attempts to reduce the weight carried into combat. Work began as a collaboration with the US Government and AAI, AAI being later purchased by Textron, and has now transitioned to a Textron development with Government oversight. Initially, concepts considered included polymer or steel conventional cases, truly “caseless” ammo, and polymer cased telescoped ammo. For reasons of performance and durability, this was downselected to polymer CT technology around 2007.
The layout of polymer CT rounds is radically different from that of conventional ammunition, consisting of a capped polymer case, with bullet surrounded by compressed propellant behind the cannelure. Consisting of a high-quality medical-grade polymer, the telescoped case reduces the overall weight of the cartridge by roughly 33%, as well as significantly reducing the overall length. In addition, the compressed nature of the powders combined with the interaction between the cap and the bullet as the round chambers leads to excellent accuracy, even in a belt-fed weapon. However, the unique nature of the polymer CT round requires a push-through ejection, and a redesigned mechanism incompatible with existing weapons.
Initial work done by the LSAT program focused on a 5.56 and later 7.62 weapon, and in this they were quite successful, indicating that the technology can be easily applied to a variety of different cartridges. In this, the requirement for entirely new weapons has a hidden benefit – as the logistics train must be built from scratch, entirely new cartridge designs with improved performance may be proposed with no downsides. Thus, the design efforts of the LSAT-turned-CTSAS program have been refocused on an entirely new 6.5mm design, and this is an extremely promising round. Consisting in it’s present configuration of a 123gr EPR projectile, the round is likely to have excellent ballistic properties, and if the cited velocities are correct, offers performance in excess of current 7.62 NATO weapons at a drastically lighter weight. Though carbine variants exist, the primary application of the 6.5 CT weapon appears to be as a light machine gun, and it is to this that we turn our attention. In addition, the requirement for new weapons gives room for far lighter weapons as well, and the advantages inherent in the 9-10lb 6.5 CT belt-fed weapon will be discussed later.
We will now briefly compare the performance of the 7.62 M240, 5.56 M249, and the developmental 6.5 CT weapon. While general quantities such as the weight of the projectile and approximate muzzle velocity are known, the rounds themselves are still developmental. The author is unaware of any openly published ballistic coefficients for the 6.5 CT round, which are necessary to determine how well the bullet maintains it’s velocity in flight. A rough approximation has been made as follows – the published diameter of 6.5mm and weight of 123grains are known. Several commercial 6.5mm 123gr bullets exist, which have G7 BCs of roughly .25 across several different manufacturers. Allowing for a 5% reduction in quality for a military loading produces the .2375 G7 BC which has been used in the following comparison.
Needless to say, the performance of the 6.5 CT round, even before the fact that it is 36% lighter than M80A1 and a lighter weapon than either the M249 or M240, is astounding. It offers a full 200m supersonic range over the 830m supersonic range of M80A1, as well as a quarter of the wind call needed at 800m. Additionally, it maintains sufficient velocity to violently fragment 100m farther than M80A1, meaning it is a more lethal cartridge as well. Compared to the M249, the comparison is more extreme in all respects, though the weight advantage in terms of ammunition is reversed. The fantastic ballistic performance of 6.5 CT may lead one to ask whether it should replace 5.56 in the fireteam’s carbines. Indeed, a 6.5 CT carbine has been proposed which more closely matches the form factor of the 5.56 carbine. Their comparison has been listed below.
The performance gap here should be readily apparent – the 6.5 CT weapon offers a further 400m of supersonic range than M855A1, a further 230m of fragmentation range, and vastly improved trajectory and wind call. Though a 6.5 CT carbine is generally a pound or more heavier than a current-issue M4A1, as well as having a lower magazine capacity, greater recoil, and higher weight of ammunition than brass-cased 5.56, to adopt such a weapon would offer vast performance benefits at range, with lesser penalties than switching to conventional 7.62 weapons. While the author would recommend maintaining a conventional 5.56 carbine, or adopting a ballistically improved 5.56 CT cartridge, the adoption of a 6.5 CT carbine as a general purpose weapon has more merit than it’s conventional contemporaries.
(6.5 CT Carbine)
Being as it is cutting edge technology, 6.5 CT (and polymer CT as a whole) has a unique and quarrelsome set of challenges. Firstly, it would require an entirely new family of weapons, logistical supplies, spare parts, and tooling to field, a process which would rival that of a new fighter jet in cost and complexity. Second, though it has demonstrated its potential, the development of polymer CT has not finished, and long-term issues such as the lifespans of weapons and endurance in harsh conditions and transit must still be studied. Particularly, the characteristics of 6.5 CT closely match those of 6.5 Creedmoor, which as discussed earlier has a markedly reduced barrel life compared to contemporary designs. Needless to say, the nature of how a CT round feeds and wears merits further study. Additionally, the increased weight and complexity of the weapons must be borne in mind – reliability and the hazards of malfunctions were noteworthy concerns during the G11 program, itself a similar development along divergent paths. Third, an oft-overlooked advantage of brass cases is that they act as immense heat sinks during firing, taking a large quantity of heat out of the weapon with each firing cycle. How polymer cased weapons (of both conventional and telescoped layouts) will deal with the buildup of heat in comparison to legacy systems remains to be seen. That the US Army is in the process of upgrading it’s M4 carbines to the M4A1 standard with a far heavier and more heat resistant barrel means this concern has weight behind it.
Lastly, the great concern is cost, especially of entirely new forms of ammunition. Though the removal of brass with its expensive forming process promises eventual cost savings, for the time being CT ammunition is markedly expensive compared to existing types, and a significant investment in manufacturing processes will be necessary to reach the economies of scale needed for a massive force such as the US Military. As a counterpoint to a predicted argument, the issue of NATO standardization is effectively moot – the US Military has adopted rifle rounds (Mk318 and M855A1) which are of questionable legality and cross-compatibility in the eyes of fellow NATO members. In the face of the massive promise of CT technology, it is unlikely the death of what remains of NATO standardization will hold the US back.
An option which has recently been proposed by General Dynamics, and which is gaining traction within the US Army, is the adoption of a machine gun intermediate between 7.62 NATO and .50 BMG. Less than a third of the weight of the M2 Browning with similar ballistics, it would do much to increase the machine gun section’s effective range. However, the Army is envisioning this machine gun as being used in the mounted or airborne role, largely due to the increased weight of it’s ammunition – almost double the weight per round of the M240. However, though this specific implementation does not exist, we shall consider a polymer cased-telescoped version of .338 Norma. We know from the fact that 5.56 to 7.62 rounds exist in polymer CT form that the technology is quite scaleable, and that a weight savings of 30% per round is roughly consistent. We compare the ballistic performance of our .338 CT weapon alongside the M240 below.
It should be clearly noted that the excellent ballistics of .338 mean that it has a much farther “point blank” range, as well as a further 530m of supersonic range. Adjusting for both elevation and wind are far easier with this weapon system, meaning it is easier to gain hits at range, especially with a novice shooter. Moreover, it’s increased mass and energy retention means that it’s downrange effects are drastically increased, and there is essentially no distance out to which it is not lethal, having over 800J at 2km. However, it is not without downsides. One of the largest downsides of 7.62 NATO, it’s increased weight, is only exacerbated, even with a polymer CT round. Brass cased .338 Norma weighs approximately double that of 7.62, with a CT .338 round being 21% more weight per round than 7.62 NATO. Moreso than with 6.5 CT, the developmental and unproven nature of the polymer CT technology is all the more unproven here, and large costs in development would likely incurred to bring a working weapon to fruition.
We shall now present the weight tallies of every option thus far considered. To begin – it is assumed that each member of the fireteam armed with a carbine carries 210 rounds of 5.56 in magazines, and 200 rounds for the SAW. If replaced with an IAR/DMR, they will carry 120 rounds for the IAR/DMR, and the IAR gunner will carry 210 rounds. It is assumed that the SAW gunner carries 500 rounds of ammunition for their weapon. It is assumed that the M240 is supported by the assistant gunner and ammo bearers carrying a sum of 1200 rounds of belted 7.62 NATO. Though unknown, the weight of the polymer links used by 6.5 CT is assumed to be half that of an M13 link used by an M240. Weights are given in pounds.
Replacing the fireteam’s carbines with 6.5 Grendel weapons would add 2.25lbs in additional weight of ammunition, and an addition pound due to having to carry an extra two magazines. Weapon weight is unchanged, which means the sum is 3.25lbs added.
Replacing the fireteam’s carbines with 7.62 weapons would add 5.45lbs in additional weight of ammunition, an additional 2lbs due to a heavier weapon, and an additional pound due to having to carry an extra two magazines. A total of 8.45lbs are added.
Replacing the fireteam’s carbines with a 6.5 CT carbine would add an additional 1.5lbs in additional weight of ammunition, an additional 1.7lb pound due to a heavier weapon, and an additional pound due to having to carry 3 extra magazines. A total of 4.2lbs are added.
Replacing the fireteam’s carbines with .264 USA weapons would add an additional pound due to having to carry 2 extra magazines, and .5lbs due to a heavier weapon. Brass cased .264 would add 2.76lbs, and polymer cased .264 would add 1.3lbs. Sums are 4.25lbs and 2.8lbs added, respectively.
Replacing the M249 with an M27 IAR type weapon would adopt a 9lb lighter weapon. 33.5lbs of belted 5.56 across the fireteam would be replaced by 22.13lbs of Mk262 in magazines. The overall load will be reduced by 20lbs for the fireteam, and the IAR gunner will see a reduction in load of 15lbs.
Replacing the M249 with an IAR type weapon in 6.5 Grendel would adopt a 9lb lighter weapon. As before, 33.5lbs of belted 5.56 would be replaced by 34lbs of 6.5 Grendel in magazines. The load reduction would, in this instance, entirely benefit the IAR gunner.
Replacing the M249 with an IAR type weapon in 7.62 NATO would adopt an 8lb lighter weapon. The 33.5lbs of belted 5.56 would be replaced by 41lbs of M118LR in magazines. Weight gains in this instance are a net neutral.
Replacing the M249 with a 6.5 CT weapon would adopt an 8lb lighter weapon. 33.5lbs of belted 5.56 would be replaced by 42lb of belted 6.5CT. Weight gains in this instance are a net neutral.
Replacing the M249 with a .264 USA weapon of unknown weight would replace 33.5lbs of belted 5.56 with 48.5lbs of brass-cased .264 USA or 41lbs of poylmer-cased .264 USA.
Replacing the M240 section with the 6.5 CT weapon would adopt a weapon 13lbs lighter. Replacing 74lbs of belted 7.62 with 46lbs of belted 6.5 CT is a weight reduction of 28lbs.
It is unknown what the relative weight would be of switching from the M240 to a weapon chambered in .264 USA or 6.5 CM. The existence of sub-10lb 7.62 machine guns suggests these weapons could conceivably be quiet light, however, we will focus purely on the ammunition weight for now. 6.5 CM would offer a weight reduction of 8lbs, whereas brass and polymer cased .264 USA would offer a weight reduction of 21lbs and 29lbs, respectively.
Adopting a .338 Norma machine gun in lieu of an M240 saves 2lbs vs the M240B, and adds 3lbs vs the M240L. Ammunition weight is essentially double that of belted 7.62, making up 160lbs of belted .338 Norma. Applying the CT technology to .338 shifts this to the more reasonable 104lbs of ammo, an increase of “only” 30lbs.
This ends this half of the article. In the following half, we will discuss explosive solutions, and discuss the proposed implementations of our solutions. I thank the reader for their endurance and their patience, and wish to see them again soon.
As one final note – I would like to gratefully thank the website shooterscalculator.com, which served as the source of my ballistic calculations and charts; the excellent work of Nathaniel F on TheFirearmsBlog, especially for his coverage of and interview with Kori Phillips, Project Officer for the LSAT/CTSAS Program as well as crafting and collating numerous EPR projectile designs and scraps of esoteric ballistician voodoo; and innumerable others for their input of data and advice. Lastly, but certainly not least (because he *does* read these) I would like to thank our gracious warlord, Winter, for his unending and beneficent patience for the time taken to finish this article. The supersonic crack of deadlines passing overhead is a frightening thing indeed.