1 ASSAULT RIFLES AND THEIR AMMUNITION: HISTORY AND PROSPECTS © Anthony G Williams, Editor IHS Jane's Weapons: Ammunition Last amended November 2016 (major re-write) Introduction First, I need to define what I mean by an "assault rifle", as there are various definitions around. The one I use is: "A standard military rifle, capable of controlled, fully-automatic fire from the shoulder, with an effective range of at least 300 metres". This raises various questions, including: "what do you mean by effective range?". This is sometimes held to be where there is a 50% chance of the average soldier hitting a human target with a single aimed shot, but in more general terms could be expressed as the range within which aimed fire is likely to hit or suppress the enemy – suppression meaning to deter the enemy from effectively fighting back or moving position, something which is achieved by near misses. Another obvious question is: "what do you mean by controlled?". There is no agreed definition, but the implication is that for automatic fire to be useful, the average infantryman should be able to keep short bursts of fire on a human target at short range, with a useful percentage of the bullets scoring hits. Controllability is affected by gun design – the shape of the stock, the type of gun action, the use of muzzle brakes or suppressors, and especially the weight of the gun – but the above definition of "assault rifle" has some clear implications for the ammunition such weapons are chambered for. First, it excludes weapons designed around pistol cartridges (i.e. machine pistols and sub-machine guns - SMGs) as they only generate around 500 joules (J) muzzle energy (ME) and cannot meet the range requirement. Second, it excludes the traditional "full power" (FP) military rifle/MG cartridges such as the .303" (7.7 x 56R) British, the .30-06 (7.62 x 63) US, the 7.92 x 57 German, the 7.62 x 54R Russian and the 7.62 x 51 NATO (typically firing 10-12 g bullets at muzzle velocities (MV) of 750- 850 m/s and developing around 3,000-4,000 J), as these are so powerful that the recoil they generate is virtually uncontrollable by the average soldier using fully- automatic rifle fire from the shoulder. Ammunition developing MEs and recoil somewhere between the SMG and FP types is needed (ME and recoil are separate calculations, but broadly linked). The history of assault rifles is very much focused on the development of the ammunition which they use. It took some time for suitable ammunition to become available. Early efforts towards light automatic weapons saw pistols such as the Mauser C96 (7.63 x 25) and P08 Luger (9 x 19 Parabellum) modified to produce carbine derivatives with detachable stocks, usually only capable of semi-automatic fire but a few with a burst-fire option. These were relatively fragile and expensive to make, however, so the future in short- range automatics lay with the much simpler blowback SMG. The first of these in 2 service (if you discount the curious twin-barrel Villar Perosa) was the Bergman MP18 in 9 x 19, which was the ancestor of the MP 38/40, the Sten Gun, the PPSh and so on. An honourable mention also to the Thompson, developed separately in the USA from 1916 onwards for their .45 Auto (11.5 x 23) cartridge. An oddity was the Pedersen Device of 1918, which replaced the bolt in the US Springfield Rifle with a semi-automatic mechanism to fire small .30 cal (7.62 x 20) pistol-type rounds developing less than 400 J; it was never used in anger. Attempts to improve the power and range of the SMGs, such as the development of the .45 Remington-Thomson in the experimental Model 1923 Thompson SMG (which used a very powerful loading developing almost three times the ME of the .45 Auto) and the use of the 9 x 25 Mauser round in the 1930s Solothurn S1-100 and Hungarian Kiraly 39M and 43M SMGs (which saw some service), did not catch on. There is a limit to the degree to which the performance of such weapons can be increased as their large-calibre, relatively light and round-nosed bullets lose velocity quickly. Also, the blowback operating system used by most SMGs is not suited to high-powered ammunition, although the Kiraly and Thompson M1923 had more sophisticated mechanisms. .30 Pedersen (7.65 x 20), .30 Mauser (7.63 x 25), 9 x 19 Parabellum, 9 x 25 Mauser, .45 Auto (11.5 x 23), .45 Remington-Thompson (11.5 x 26), 5.7 x 28 FN, 4.6 x 30 HK, 5.8 x 21 DAP-92. More recently, small-calibre high-velocity PDW ammunition has emerged (described in more detail in a separate article1). The FN 5.7 x 28 has achieved some sales, in both the Five-seveN pistol and the P90 SMG, as has the rival HK 4.6 x 30 in the MP7. However, despite their improved range performance, these cartridges still only develop around 500 J so don't qualify as assault rifle ammunition. The Chinese 5.8 x 21 DAP-92 is even less powerful. At the other end of the power scale there were many attempts from the beginning of the 20th century to increase the firepower of the FP infantry rifle by replacing its manual bolt-action with a self-loading mechanism (some of them shown below). However, such weapons did not enter general service as standard infantry rifles until the US M1 Garand in 1937. 1 http://quarryhs.co.uk/PDWs.htm 3 Some early semi-automatic rifles, from top to bottom: 1918 .303 Farquhar Hill; 1909 Mondragon (7.92 mm); 1917 MAT Mk 1917; 1929 Czech Brno Z.H.29 (photo taken at MoD Defence Academy, Shrivenham) Attempts to make such weapons fully automatic ran into difficulties due to their heavy recoil. Perhaps the most successful examples were the WW2 German FG 42 paratroop rifle in 7.9 x 57 and the postwar Swiss Stgw.57 in 7.5 x 55, but these were significantly heavier than contemporary rifles, the weight helping to absorb the recoil. This is even more true of the US Browning Automatic Rifle (BAR) in .30-06 which was even heavier, weighing about twice as much as a "standard military rifle"; its low rate of fire also helped controllability. Some of the early rifles in 7.62 x 51 NATO, such as the US M14, German G3 and some versions of the FN FAL, were also capable of fully automatic fire, but the recoil problem made them more or less uncontrollable so they cannot be classified as assault rifles. Assault rifles therefore need to be designed around a cartridge intermediate in ME between SMG and FP rifle rounds; in practice, approximately in the 1,250-2,500 J range depending on the calibre. There have been two contrasting approaches to the design of a suitable cartridge with the appropriate compromise between long range and light recoil. One is to retain the same 7.5-8 mm calibre as the FP round, but with a shorter cartridge case firing a lighter bullet at a lower muzzle velocity (lets call these "full calibre assault rifle", or FCAR, rounds). The other is to reduce the calibre 4 while retaining the same, or a higher, velocity (reduced calibre, or RCAR rounds). FCAR rounds score well in the traditional methods of measuring barrier penetration and terminal effectiveness (dominated by calibre and bullet weight) and also by being less affected by the bullets striking foliage etc on their way to the target. However, they have a relatively steep trajectory and a rapid velocity loss due to the short, fat bullets, which quickly reduces their effectiveness at long range. The full-power 7.9 x 57, 7.5 x 55, .30-06 and 7.62 x 51, shown next to the 7.62 x 39 and 5.56 x 45 which are the most common FCAR and RCAR rounds respectively A decision to reduce the calibre raises the immediate question; by how much? At the large end of the RCAR scale (7 mm), bullet weight and MV can be much the same as in the FCAR cartridges, but the better ballistic coefficient (BC) due to the longer and more slender bullet will reduce velocity loss and improve long-range performance. As the calibre decreases, so the recoil and the ammunition weight become lighter and the MV can be higher, thereby flattening the trajectory; all good things. The downside is that barrier penetration may be reduced and stopping power becomes more controversial (relying on velocity and rapid bullet yaw on impact rather than calibre and bullet mass; which according to combat reports sometimes works, sometimes doesn't). The long-range performance also begins to decrease as small-calibre bullets generally have BCs which are inferior to large-calibre ones. Different nations have made different choices in developing assault rifles, and the purpose of this article is to describe and explain them in order to examine the future prospects for this type of weapon. 5 Developments up to 1918 The elements of an assault rifle were in place surprisingly early in the history of automatic weapons. The first selective fire (semi or full auto) rifle was probably the Italian Cei-Rigotti, developed between 1900 and 1905 around a 6.5 mm cartridge with less power and recoil than the usual 7.5-8 mm FP types, but this was not adopted. Mannlicher introduced a Self-Loading Carbine in 7.65 x 32 calibre, an improved and enlarged version of their Model 1901 pistol carbine chambered for a lengthened version of the 7.63 x 25 pistol round, which was made in 1904. It never went past the prototype stage and its ballistics are not known. However, the cartridge case is similar in length as well as calibre to the US .30 M1 Carbine's, but slightly fatter as it is bottle-necked. Mannlicher Carbine in 7.65 x 32 calibre (courtesy of Geoff Sturgess) The first service weapon which can be identified as conforming to the specification of an assault rifle dates back to the First World War; the Russian Federov Avtomat of 1916. This was a selective fire weapon using a short-recoil action. It was originally chambered for Federov's own purpose-designed high-velocity 6.5 mm cartridge, but as the Great War was then underway there was no chance of a new cartridge being adopted, so he modified his gun to use the Japanese 6.5 x 50SR Arisaka cartridge, large quantities of the guns and ammunition having been acquired by Russia to meet a shortfall in their supply of rifles. This was a happy accident, as the cartridge combined moderate recoil with a good long-range performance, but only a few thousand Avtomats were made. They were used in action in the Russian Civil War and also as late as the Winter War with Finland in 1939-40, and thereby earned their place in small-arms history. Federov Avtomat It can be argued that neither the Cei-Rigotti nor the Federov Avtomat used 6 "intermediate" cartridges, as the 6.5 mm Carcano and Arisaka were the front-line rifle/MG rounds in the Italian and Japanese armies respectively. This is true, but it is worth bearing in mind that, in terms of calibre and muzzle energy, they were in the same class as the present-day 6.8 x 43 Remington SPC and 6.5 x 38 Grendel, which are today regarded by many as ideal intermediate cartridges for assault rifles. 8 mm Ribeyrolles The French also nearly made it into the record books with the first selective-fire rifle using purpose-designed intermediate ammunition. During WW1 they made some use of the semi-automatic Winchester Model 1907 in .351" (8.9 mm) and the Model 1910 in .401" (10.2 mm) Win SL (self-loading) cartridges; the rifle design was very simple, being blowback only. While these were mainly used by aircrew, in 1917 France placed an order for 2,200 of an automatic version of the M1907 for use by special assault soldiers. At the same time, they were modifying the .351 SL cartridge by necking it down to accept an 8 mm rifle bullet, creating the 8 mm Ribeyrolles – arguably the first purpose-designed intermediate military cartridge. This was tested in July 1918 and found to be effective out to 400 m. The war ended before anything came of this, but it is not hard to see that had it lasted for another year or two, French troops could have been equipped with an assault rifle. As it was, neither the Ribeyrolles, nor a 7 mm version designed in the 1920s, made further progress. Another very interesting weapon and ammunition combination which emerged in 1918-19 was the Winchester Machine Rifle in .345 calibre, designed by Frank Burton. The cartridge was simply the .351 Win SL loaded with a pointed 11.2 g (173 grain) bullet fired at an MV of 564 m/s (1,849 fps). The gun weighed 4.5 kg (10 lb) and was 116 cm long (45.5") with a barrel length of 63.5 cm (25"). It used a blowback action and fired from an open bolt; it had selective fire, with a cyclic rate on automatic of 800 rpm. The most interesting aspect was the unique ammunition feed, which consisted of two box magazines, top-mounted but in a vee-form or butterfly wing layout. The capacity of each magazine is commonly said to be 40 rounds, although the Winchester museum (which has the only surviving example) states 25 rounds. This layout had several advantages over other top-mounted magazine feeds: • increased ammunition capacity without needing an excessively tall magazine • an empty magazine could be replaced while keeping the gun instantly available to fire using the other magazine • the sights were ambidextrous: on the centreline with the sight-line between the magazines, instead using sights offset to one side (as in e.g. the Bren gun). Unfortunately this weapon did not proceed past the prototype stage. 7 Above and below: Winchester Machine Rifle, showing the unique magazine layout 6.5 x 52 Italian, 6.5 x 50SR Japanese Type 30, 7.65 x 32 Mannlicher, .351 Winchester SL, .345 Machine Rifle, 8 mm Ribeyrolles (replica) 8 The interwar period Interest in assault rifles on the part of the major powers then largely disappeared from view until the Second World War, although experiments continued in some smaller countries, especially Switzerland. Their prolific gun designer Fürrer produced a short-recoil carbine with a new bottle-necked 7.65 x 35 cartridge in 1921. We are now getting very close to the concept – except that the cartridge had a round-nosed rather than pointed bullet. A year later a modified 7.65 x 38 appeared which did have a pointed bullet. Swiss sources indicate that data from the tests of these rounds were passed to DWM in Germany, where they may have influenced later developments. Other pre-Second World War Swiss short-case ammunition designs included a different and rather mysterious 7.65 x 38 round for which unloaded components were made in some quantity, for an unknown destination, just before the war. In Italy the Terni Model 1921 selective-fire carbine emerged: the cartridge was a 7.35 x 32 rimless round, a shortened and necked-out version of the standard 6.5 x 52, which fired a pointed 8.7 g (134.5 grain) bullet at a claimed 600 m/s (1,970 fps). In the early 1930s, the US Frankford Arsenal tested this rifle, or one very like it. Various other Italian experiments took place throughout the interwar years, but to no effect: the 7.35 x 51 round eventually selected was designed to be used in rebarrelled 6.5 mm weapons (they increased the calibre because it was cheaper to rebore existing worn-out barrels instead of buying new ones), but it was at least loaded to quite modest levels in recognition of the fact that long range was not required. In 1925 Kynoch of the UK proposed a "7 mm light automatic rifle cartridge" intended for BSA. The factory drawing shows a bottle-necked case with a length of 41 mm and a round-nosed bullet. It is not clear whether the cartridge or gun were ever built. In Russia, Federov continued to argue for the adoption of a smaller cartridge than the 7.62 x 54R. In the late 1920s he recommended adoption of the 6.5 mm calibre "if not even smaller" and a rimless or semi-rimmed case with a length shortened by about 20 % (to 40 mm). His ideas were supported in 1930 by V.E. Markevich, of the Red Army's Weapons Scientific and Research Range, who pointed out that an ideal 9 cartridge already existed – in the .25" Remington hunting round! The bigger brother based on the same case, the .30" Remington, was used much later as the starting point for the development of the 6.8 mm Remington Special Purpose Cartridge. In the early 1930s Denmark made limited numbers of the delayed-blowback Weibel (or Danrif) M/32 assault rifle in a 7 x 44 calibre. From this rifle, the 8 gram (123 grain) bullet reportedly achieved a muzzle velocity of 750 m/sec (2,460 fps) for an ME of 2,250 J. In 1939 a light automatic weapon was advertised in Greece in 7.92 x 36 calibre, the cartridge apparently being based on a shortened and necked-out 6.5 mm Mannlicher case. In fact, despite the evidence that most small-arms engagements during WW1 were at short range, armies showed more interest in new FP rifle/MG rounds. The Japanese Army began to replace their 6.5 x 50SR cartridge with a new 7.7 x 58 calibre, although they never completed the changeover. The Italians were similarly caught at the start of WW2 part-way through a change from their 6.5 x 52 Mannlicher-Carcano rifle to a 7.35 x 51 calibre. This happened for several reasons. One was that long- range MG fire was considered essential: the first Japanese Army 7.7 mm round was only available in MGs (the first 7.7 mm rifles only emerging about a decade later), and other powerful MG rounds (e.g. the 8 mm Breda, 8 mm Bofors and 8 mm Solothurn) were introduced during this period. Swiss 7.65 x 35, Swiss 7.65 x 38 with bullet, .276 Pedersen (7 x 51), 7.35 x 52 Italian 10 For the most part, the introduction of rifles in the new MG calibres seems to have been to simplify ammunition supply arrangements, rather than because the smaller calibre rifles were felt to be ineffective. Finally, the need for a full-auto rifle (and therefore lower-powered ammunition with less recoil) was not recognised and probably generally resisted, on the grounds of economy (automatic rifles being much more expensive and requiring more maintenance than bolt-action ones), and also the fear that soldiers would just spray ammunition around at a great rate, causing increased cost and supply problems (this latter concern was, of course, fully justified, but was addressed by improving supply arrangements). So even the one nation wealthy enough to afford an automatic rifle – the USA – restricted the M1 Garand to semi-auto fire, and FP rounds biased towards MG use prevailed. There had been some efforts towards considering intermediate calibres, with the US Ordnance Board sponsoring comparative trials in the early 1930s of the effectiveness of different rifle cartridges using anaesthetised pigs and goats to assess wounding effectiveness. They concentrated on a .256" (6.5 mm), a .276" and the existing .30". The .256" (8 g at 820 m/s, for 2,700 J - much more powerful than the .25" Remington) most impressed the testers, but the Board chose the .276" Pedersen (7 x 51) developing 2,400 J (similar in power to the 6.5 mm Arisaka, the later 7 x 43 British and the modern 6.8 mm Remington). However, the army was still thinking in terms of long-range semi-automatic fire, a mindset which did not change until the 1960s. The .276" cartridge was rejected in 1932, partly for cost reasons but also because it did not offer sufficient long-range performance. World War 2 - the Assault Rifle Emerges In the run-up to World War 2, the focus switches to Germany. In the aftermath of the Great War a Hauptmann Piderit of the German Rifle Testing Commission had advocated a short-cased cartridge and a suitable rifle to fire it, but his was a lone voice. It wasn't until 1927 that DWM (actually, the "Berlin-Karlsruher Industriewerke A.G." as DWM was known between 1922 and 1936) carried out the first tests of short-cased cartridges, possibly as a result of the data they had received about the Swiss rounds, but these had no direct result. It wasn't until the mid-1930s that serious work got underway, and over the next decade no fewer than five German companies were involved in developing short-cased cartridges suitable for assault rifles: Geco, DWM, RWS, Rheinmetall-Borsig and Polte. Geco was the first in the field, co-operating with the gun company Vollmer-Werke Maschinenfabrik to produce the Vollmer SL Model 35 self-loading carbine in a nominal 7.75 x 40 calibre (the calibre was actually 7.9 mm, with a bullet 8.05 mm in diameter). This was officially tested with good results, but led to no orders. In 1942 Geco produced a new cartridge also intended for a Vollmer carbine, the 7 x 45SR. This used a wider case and was far more powerful, with a muzzle velocity of 1,000 m/s. Another cartridge, measuring 7.9 x 33.5, was designed at Geco and attributed to H.G. Winter, a director of the firm, but the date and the gun for which it was intended are not known.