The Late History: EF88 and M4 spinoffs
The period from 1990 – 2009 saw substantial iteration on the M4 and AR15 design, but little substantial development of the F88 and AUG. Notwithstanding numerous minor product improvements to the M4 in the period after, the trend was reversed in the 2010s with substantial development of the F88 and little development of the M4A1 in military service.
The EF88 was everything to the development of the F88 that the SA1 and 2 wasn’t. It reduced the weight of the rifle back down to 3.4kg and made numerous substantial changes to the workings of the system. The barrel was changed to a fluted design to reduce weight. The aluminium receiver was changed in design and materials to reduce weight and the barrel mounting was changed to improve accuracy. The configuration of the butt group was changed to reduce the length of pull to better accommodate body armour. The trigger weight was decreased. Additional accessory rails were added to the right- and under-side and the integral foregrip was removed. A new and lighter grenade launcher that could accept longer 40mm cartridges (the SL40) was mated to the system. Initially intended as a firearm only for combat arms (infantry, artillery observers, combat engineers) the weapon exceeded initial expectations and was acquired as a replacement for the F88SA2 for most regular forces. A number of other accessories and improvements to the platform remain in the process of acquisition with a near term (but not entirely clear) rollout schedule, including suppressors, simunition kits (airsoft and man marking munitions) and a case deflector[i].
In the same period, substantial development of the M4 did not occur, but some evolution of the basic pattern did in non-military service. Companies such as Lewis Machine and Tool (LMT) made additional developments to the basic design mainly intended to ease multicalibre modularity and improve reliability (monolithic upper receiver designs, more modular barrel assemblies, different gas key, gas-port and bolt-port configurations, new bolt materials). While there is absolutely no question that these latest iterations of the AR15 design are excellent weapons, they tend to be disproportionately more expensive, in large part because the AR15 design is so refined that additional developments require very high effort for even marginal returns. For example the (somewhat troubled) NZDF acquisition of 9040 examples of the LMT Modular Assault Rifle – Light for $59 million (NZD)[ii] compared to the ADF acquisition of the EF88 (which it did not trial against) of 30,000 for $100 million (AUD)[iii]. The difference in cost is generally traded off against the acquisition of better quality and more comprehensive accessory sets.
Development of the offshoots of the SCAR program have continued, with the piston-driven AR15 concept seeing substantial military interest, for example the HK416 by the French and Dutch armies, a version of the HK416 (the M27 IAR) by the USMC, and the Caracal CAR814 by the Indian Army. Short barrelled versions of the HK416 have also seen adoption by elements of US SOCOM and Australian SOCOMD, but despite their much improved reliability over the M4A1, they are understood to generally be much less popular with special operators than direct impingement AR15s due to their greater weight, higher recoil impulse and substantial gas blowback[iv].
United States Marine Corps / 120322-M-PH863-005
The Status Quo
The status quo is that the EF88, M4A1 and its derivatives are all excellent individual weapons with subtly varying profiles of strengths and weaknesses that defy strict univariate apples to apples comparison. In a general sense, direct-impingement AR15 designs are generally considered to be more ergonomic, handle better and are slightly lighter than the EF88 which is much more reliable[v], much more durable and slightly more lethal at any given configuration’s overall length (5.56mm ammunition fired from it retains the necessary velocity of 2500 feet per second for remote wounding by temporary cavitation[vi] and fragmentation[vii] for about 70m longer – about 125m for a US Army M4, about 190m for an EF88 in ideal conditions, and 70m and 130m in cold weather or with a worn barrel). Piston driven AR15 derivatives like the HK416 are about as ergonomic as the M4 and seem to be about as reliable and durable as the EF88[viii], but are heavier than either and have lethality on par with the M4 for any given length. All three rifle families are highly accessorisable using the ubiquitous MIL-STD 1913 rail system; the M4A1 and HK416 have an additional rail on the left hand side of the weapon, and their side rails are slightly longer with most furniture options, but all of the rifles have such ample rail space that the extra space is of marginal benefit outside of niche cases. The M4A1 has a much, much larger and more diverse aftermarket for parts and rebuilding options than the other rifles, but all are of roughly similar overall cost.
An aside on lethality – how much does cavitation tearing matter?
All things being equal, shooting someone with a bullet travelling faster than about 2,500 feet per second probably roughly doubles the chance of the bullet killing them compared to a bullet travelling slower than about 2,500 feet per second.
There are two ways that bullets kill people – by disabling the central nervous system or by blood loss. The former is instant, the latter takes time varying from a few seconds to hours depending on what is hit. Shot placement is the primary determinant of the lethality of any round, but having a larger or hollowpoint or open-tip match or fragmenting bullet that pierces more tissue provides an increase in the likelihood of a bullet or one of its fragments passing through a vital tissue or major blood vessel. However, there is a second wounding mechanism available to bullets – when a bullet enters the body it crushes and pierces tissue in front of it and pushes it to the side which creates a shockwave that travels through tissue – if the shockwave travels faster than the ability of tissue to stretch or too far for it to stretch then it tears it instead. When this occurs, it can cause serious wounds some distance away from the path of the bullet. The speed at which that reliably occurs is about 2,500 feet per second (in terms of the projectile’s speed in air; the shockwave travels faster in flesh). These shockwaves can be surprisingly powerful; even in the absence of the cavitation causing permanent tears, the shockwaves can be powerful enough to break bones[ix].
A veteran police officer and firearms instructor by the name of Greg Ellifritz conducted a study of about 1,800 shootings over 10 years and found that pistol calibres, irrespective of size and power, consistently kill about 20-30% of people shot with them while centrefire rifle calibres consistently kill about 70% of people shot with them. The difference between all pistol calibres (where tripling the power from 9mm Parabellum at 500 joules of energy to .44 Magnum at up to 1,700 joules of energy makes no substantial difference in the ability to kill) and centrefire rifle calibres seems to be the increase in velocity to the threshold above 2,500 feet per second. A 5.56x45mm round has similar muzzle energy to a .44 Magnum but is travelling at about 3,000 feet per second at the muzzle compared to about 1,450 feet per second for the .44 Magnum. Shotguns are also extremely lethal, but probably for different reasons (shot does nasty things to the human body)