ASSAULT RIFLES AND THEIR AMMUNITION: HISTORY AND PROSPECTS © Anthony G Williams ...

43 Pages·2016·2.41 MB·English

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.