An Introduction to Anti-Tank Rifle Cartridges

 

© Anthony G Williams

 

This article was first published in the November and December 2004 issues of 'The Cartridge Researcher',

the Bulletin of the European Cartridge Research Association. Modified January 2013, with thanks to Szymon Sztetner

 

Small and medium bores

 

The anti-tank rifle (ATR) had a short life, entering service towards the end of the First World War and being almost entirely replaced part-way through the Second. During that time, some interesting specialist cartridges were developed for them as well as some existing rounds adopted for their use.

 

The first anti-tank rifle to see service was the German Mauser T-Gewehr M1918 firing a 13 x 92SR cartridge. This round was originally designed for a large Maxim-type HMG (heavy machine gun) generally known as the T.u.F. (for Tank und Flieger, the intended targets) but although mass production was starting only a couple of dozen of these were completed by the end of the war. The Mauser rifle was seen as a quicker and simpler way of getting the powerful cartridge into service; it was needed urgently as its penetration of up to 20 mm enabled it to pierce the armour of the Allied tanks. Despite its limited use, the cartridge is commonly available to collectors.

 

There was considerable interest in developing new ATRs in the 1930s and several nations introduced weapons into service. They can be divided into three categories: medium calibre (12.7-15 mm) directly inspired by the Mauser, small-bore high velocity rounds of 7.92 mm calibre, and big 20+ mm weapons which generally required at least two men to carry them.

 

One of the best-known of the medium-calibre ATRs is the British Boys Rifle, which fired a unique .55 inch cartridge (13.9 x 99B). This was based on the .50 Browning HMG round, with the calibre increased and a belt added. Two different AP loadings saw service (W. Mark 1 and W. Mark 2) and in the UK these are the easiest and least expensive rounds to collect. Performance was no better than the Mauser's. There was a tungsten / light alloy APCR loading with much superior performance which was made in some numbers and tested operationally, but it was too late and never adopted. That loading is extremely rare but instantly recognisable because of the two-part bullet.

 

The Russians initially copied the Mauser M1918, just rechambering it for their 12.7 x 108 HMG round to produce the Sholoklov. However, the performance was unsatisfactory so they developed a far more powerful cartridge – the 14.5 x 114 – and produced two different ATRs to fire it: the simple PTRD and the more complex (and less popular) semi-automatic PTRS. Performance was greatly improved with penetration of up to 40 mm at short range, helped by tungsten-cored AP bullets in the BS.41 loading (a steel-cored B.32 was also used). The ATRs largely disappeared after WW2, although they were still around in Korea, but the cartridge has survived because a new HMG was developed around it – the KPV – which is still in service today. As a result, the typical steel-cased Russian rounds are readily available to collectors, although finding a brass-cased WW 2 ATR round is a very different matter!

 

The key component in penetrating armour is velocity, so designers in two separate countries coincidentally decided that a high velocity could be combined with moderate size and recoil by selecting a smaller calibre. The countries were Germany and Poland and the cartridges the 7.92 x 94 Patronen 318 'Panzerbüchse' and 7.92 x 107 respectively.  The former was chambered in the PzB 38 and 39, and the M.SS 41 bullpup. It is famous for having a 'tear gas' pellet at the base of the bullet. The Polish cartridge was used in the Kb Ur wz 35, better known as the Maroszek after the leader of the design team. Both were capable of up to 1,200 m/s muzzle velocity but barrel erosion was severe leading to a rapid fall-off in performance.  The Patronen 318 was loaded with a tungsten-cored bullet which was capable of penetrating up to 30 mm armour at short range. Unusually, the Polish bullet didn't have a hard core - it was just lead. The principle of armour piercing was different from other AT rifles. It was not supposed to pierce the armour but to "stick" to it, and give it all its kinetic energy. The result wasn't to pierce but rather to break the armour at the point of impact. During tests, the projectile produced a "cork" of about 20mm in diameter in the armour which flew into the tank at high velocity. These rounds are not difficult to find, but are much more costly than the ones described so far.

 

As well as the service rounds described above, there have been many experimental ATR rounds, most of which are very rare. The smallest is probably the 7.92 x 87 Spanish cartridge which was being developed at around the time of their Civil War. It is rumoured that the only rifle made was actually used in the war, but it is believed that only one genuine round survives. You will find these cartridges for sale, but they are replicas – a batch was made some years ago. Another rare round available as a replica is the German 13 x 94, which was an interim development between the 13.2 x 92SR and the 7.92 x 94.  Before adopting the Lahti L/39 Finland experimented with ATRs firing various 13.2 mm calibre cartridges, the final version being a powerful and unique 13 x 118B round – these survive in a Finnish museum but not, as far as I know, anywhere else.

 

Finally, there is one experimental ATR round which is quite commonly available – the American .60 inch (15.2 x 114). The reason for this is that although the big, gas-operated T1E1 ATR it was designed for was cancelled, the round was adopted for various aircraft MG projects during and after WW2. During this process it was necked down (to make the .50/60) but eventually reached production status when it was necked up to 20 mm to create the 20 x 102 used in the M39 and M61 Vulcan aircraft guns.

 

Table of Anti-Tank Rifle Cartridges of up to 15 mm/.60 inch Calibre

 

Calibre

Rim diam mm

Body diam mm

Bullet weight g

Muzzle velocity m/s

Muzzle energy j

Guns

7.92x87

13.4

13.4

?

?

?

Spanish ATR

7.92x94

20.9

21.1

14.3

1,210

10,500

PzB 38/9, M.SS 41

7.92x107

16.4

16.5

12.8

1,220

9,500

Maroszek

12.7x108

21.8

21.8

52

860

19,200

Sholoklov

13x92SR

23.1

20.9

52

770

15,400

M1918

13.9x99B

20.3

20.4

47.6

884

18,600

.55 Boys

14.5x114

26.9

26.9

64

1,000

32,000

PTRD, PTRS

15.2x114

29.5

29.2

76.5

1,100

46,000

.60 T1E1

 


 

20+ mm Calibre

 

The most spectacular of the ATRs were the big guns of 20 mm or more calibre. Several different cartridges were used in these guns.

 

Oerlikon of Switzerland produced two self-loading ATRs using ammunition developed for their automatic cannon. The first was the SSG, chambered for the 20 x 72RB round from the FF aircraft gun. The second was the SSG-36, chambered for the much more powerful 20 x 110RB cartridge as used in the famous Type S AA gun and the FFS aircraft gun. The larger cartridge is easily available – but usually with HE projectiles, the AP being much less common. The small FF saw little use in Europe and the round is hard to find in any loading.

 

Solothurn in Switzerland, which carried out much interwar development work for Rheinmetall-Borsig of Germany, introduced the self-loading S18-100 series (the numbers of the variants went up to S18-500) in a unique 20 x 105B calibre. This round was later used to develop an aircraft cannon, the Lb 204, although by the time this was adopted for use in German naval aircraft as the MG 204 the case design had been changed slightly to a rimless 20 x 105. The S18-100 series was quite widely used and the rounds are not too difficult to find.

 

The next step up in power was the Japanese Type 97 which fired a specially-designed 20 x 125 round. This was a self-loading gun from which was developed the Ho-1 and Ho-3 automatic aircraft cannon in the same calibre (the Type 97 is often stated to have been automatic but that was not the case). The ammunition is hard to find.

 

One cartridge was used by two different ATRs. This was the 20 x 138B 'Long Solothurn' originally designed for a range of Swiss / German developed automatic cannon which saw service in WW2 as the FlaK and KwK 30/38 and the MG C/30L. As a result, the cartridge is the easiest to find of the big ATR rounds. The ATRs in this calibre were the Swiss Solothurn S18-1000/1100 and the Finnish Lahti L/39. The self-loading S18-1000 was a scaled-up version of the earlier S18-100 series. The S18-1100 was similar but automatic in operation; this facility being probably intended for AA use on a special mounting. Similarly, the self-loading Lahti, which is famous both for the little skis with which its bipod could be fitted and its imposing muzzle brake, was available in an automatic version for AA use. The Finns manufactured their own ammunition for this gun, headstamped Tikkakoski (or just T) from the arsenal where it was made.

 

Two other 20 mm guns were advertised as suitable for the anti-tank role, although they were issued on more substantial mountings. These were the Madsen in their own 20 x 120 calibre (the cartridges are not common) and the Bofors m/40, also firing their own 20 x 145R round – which is very rare. These weapons were both more commonly encountered as AA guns in high-angle mountings.

 

A complete contrast was the 20 mm Swedish Carl Gustav m/42. Unlike all of the other high-velocity ATRs this was recoilless and looked like a very slim version of the postwar 84 mm Carl Gustav anti-tank weapon which was developed from it. It was very much lighter and handier than the other 20 mm ATRs, but was a single-loading weapon with each cartridge needing to be chambered by hand. In order to provide the gas necessary to balance the recoil, the 20 x 180R cartridge case was huge and featured a blow-out panel in the base. These are rare but do occasionally come onto the market.

 

The final one of the service rounds is pushing the ATR category as it is approaching light artillery; the Swiss 24 mm Tb.41 (Tankbüchse) This was a self-loading gun firing a powerful 24 x 139 cartridge which was also used in the similar Pzw-Kan 38 AFV gun. Once again, this round is rather rare.

 

ATRs were of course replaced by large-calibre weapons firing HEAT charges. However, modern equivalents have recently become very popular as anti-material or long-range sniping rifles. These are usually available in .50 Browning (12.7x99) or the Russian equivalent (12.7x108) but can also be obtained in 14.5x114 and several different 20 mm calibres.

 

Table of Anti-Tank Rifle Cartridges of 20+ mm Calibre

 

Calibre

Rim diam mm

Body diam mm

Bullet weight g

Muzzle velocity m/s

Muzzle energy j

Guns

20 x 72RB

19.0

21.9

128

600

23,000

Oe SSG

20 x 105B

25.0

25.0

140

730

37,000

S18-100

20 x 110RB

21.9

24.9

122

830

42,000

Oe SSg 36

20 x 120

28.9

29.0

154

780

47,000

Madsen

20 x 125

28.5

28.7

162

790

50,000

Type 97

20 x 138B

27.0

27.0

147

795

47,000

S18-1000, Lahti L39

20 x 145R

29.5

25.4

145

815

48,000

Bofors m/40

20 x 180R

47.9

42.6

108

950

49,000

CarlGustav m/42

24 x 139

31.4

32.0

225

900

91,000

Tb 41

 

 

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