Development of German Tank and Antitank Guns, WWII Tactical and Technical Trends, No. 26, June 3, 1943 (Lone Sentry)

A detailed analysis of the chronological development of German tank and antitank guns is presented in the following report, which is preceded by an examination into the basic requirements for tank and antitank guns. All of the information contained in this article comes from British sources.

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a. Theory

In order to bring into proper perspective the various lines of German antitank and tank gun development, it may be useful first to consider various factors which influence design, and to consider also the effect of design on both actual performance and lethal or destructive effect.

(1) The Problems of the AT Gun

The principal requirements for an antitank gun are the following:

(a) Ability to perforate the enemy's tank armor at the maximum range at which accurate engagement can take place;

(b) A projectile which will not only penetrate the armor but cause sufficient mechanical damage inside the tank, or personnel casualties, to disable the tank as a fighting vehicle;

(c) Ease of maneuver and concealment, requiring a carriage and a total weight which will permit speed into and out of action, and a low silhouette;

(d) A high rate of fire, a flat trajectory, and an accurate sight to enable it to engage relatively small and moving targets;

(e) Protection for the gun crew against machine-gun fire as a minimum, and against AP and HE projectiles and bomb near-misses as an optimum;

(f) An HE projectile which will enable the gun effectively to engage soft-skinned targets, when the opportunity offers and does not conflict with the gun's primary task.

(2) The Problems of the Tank Gun

Insofar as a tank gun under modern conditions is expected to be able to deal with enemy armor, most of these same conditions will apply, with an additional condition imposed by the need for economy of space in a tank.

(3) The Problems of Projectiles

(a) General

The ability of a projectile to penetrate armor depends to a great extent on the velocity at which it strikes the target, and to a lesser extent on its weight and on the angle at which it strikes. It follows, therefore, that given equality of projectile design, material, weight, and angle of strike, the higher the muzzle velocity at which the projectile is fired, the greater the thickness of armor which will be penetrated at a given range.

It also follows that given equal muzzle velocity and quality of projectile design and material, the heavier the projectile the less the penetration performance will decrease as range increases, since the heavier projectile maintains its speed through the air better and the descending curve of remaining velocity is flatter.

The heavier the projectile, the more difficult it becomes to achieve in practice a high muzzle velocity without being forced by mechanical considerations to heavy guns and bulky ammunition. Hence the antitank gun-designer is immediately faced with several problems. Is he prepared to accept a light projectile with a high muzzle velocity, relatively rapid deceleration, loss of striking power at longer ranges, and relatively slight lethal effect, in order to be sure of penetrating thick armor at the shorter ranges? If he is, he will have to take a chance on securing a direct hit on a vital spot to get results.

Is he prepared to accept a lower scale of penetration at the shorter ranges with a heavier projectile, which will, however, keep up its performance better, and do more damage at extreme ranges wherever he gets a hit? And if he decides to take as his target a thickness of armor of X inches, which no normal antitank gun of manageable proportions will defeat, how is he going to get the extra velocity to drive his projectile through it?

(b) A German Solution: The Tapered-Bore Gun

In general, increased velocity can be obtained in three ways: by increasing the pressure in the gun behind the projectile, by lengthening within limits the bore of the gun (and consequently the travel of the projectile under pressure), or by increasing the area of projectile upon which a given pressure acts. The first method increases the weight of the gun; the second also gives an unmanageable barrel for field purposes (for instance, a 3-inch high-velocity gun, using suitable propellant, might require a barrel length of about 100 calibers, or 25 feet); the third tends to give a projectile of bad ballistic shape. The tapered-bore or Guerlich design adopted by the Germans for certain of their weapons employs the third method, but gets over the disadvantage mentioned by gradually reducing the base area of the projectile as it travels through the bore, thus bringing it to a proper ballistic shape by the time it leaves the muzzle.

With the Guerlich design they have managed to produce guns of light weight capable of penetrating exceptional thicknesses of armor at the shorter ranges of engagement. For this performance they have had to sacrifice a great part of the destructive effect inside the tank. A projectile from a straight-bore weapon of, for instance, 3-inch caliber weighs about 15 pounds, and in penetrating the armor not only throws into the tank large pieces of disrupted armor from a 3-inch hole, but follows through either intact, or in fairly large fragments, to cause widespread damage. On the other hand, the projectile from a tapered-bore gun of the same entrant caliber weighs only about 6 pounds and will emerge as slightly less than 2 1/4-inch caliber. Owing to its design it will only force a hole of about 1 1/4-inch diameter in the armor, and owing to the material of the core, internal damage will be restricted to that done by small fragments within a fairly narrow cone opening out from the point of impact.

It must also be borne in mind that with high velocity (i.e., greater than about 3,500 f/s muzzle velocity), it is necessary to employ a tungsten carbide core to enable the projectile to give full penetrative value for its high velocity. The necessary raw material (wolframite) is not in such generous supply that the wholesale arming of every antitank gun with such a projectile could be contemplated.

In the event of a hit failing to penetrate, damage done by the light high-velocity projectile will be negligible compared with that caused by the equivalent normal projectile. However, taking everything into consideration, the tapered-bore gun is potentially a very serious threat to the heavier armor, particularly if a succession of hits can be obtained; but if only one hit is obtained, the probabilities of causing immediately disabling damage are relatively low. It is not a weapon which can, with advantage, engage in long-range duels with any adequately armed tank.

It would not for instance prove profitable in the open African desert, where duels at ranges of up to 2,500 yards are common, but in the close conditions of some European countrysides it might find all the conditions for its profitable employment satisfied. In more open conditions, the normal straight-bore weapon with its heavy projectile will have every advantage.

With a tapered bore, effective engagement of soft-skinned targets is difficult of fulfillment. High performances with both AP and HE projectiles from the same gun are incompatible, and while it is possible to compromise with a normal straight-bore weapon, losing a bit each way, there can be no compromise with a tapered-bore antitank gun, and HE performance must be sacrificed.

b. Developments

The rapidity with which the German forces have expanded and developed their tank and antitank armament is among the outstanding technical performances of this war. New weapons have appeared in quick succession, in turn to be superseded or improved, and throughout there has been a parallel development and improvement of ammunition.

At the end of 1939, the German Army had one standard antitank gun, the 37-mm Pak. To supplement this, they had to call on the heavy antiaircraft equipment, the 88-mm Flak. They had tank guns of 1934 vintage, the 20-mm Kw.K 30, the 37-mm Kw.K, and the 75-mm Kw.K. The antiarmor performance of tank guns was low.

Early in 1941, the German Army had, in addition to the 37-mm Pak, a new 28-mm tapered-bore,* light antitank gun, the Pz.B** 41, primarily for airborne troops and infantry, and a new 50-mm antitank gun, the 50-mm Pak 38. As a stop-gap, the Czech 47-mm antitank gun was also being used. The 37-mm Kw.K had been dropped from their tank armament, and in its place came a moderately effective 50-mm tank gun, the 50-mm Kw.K.

In addition, early in 1942 the German Army had put to use as an antitank gun the Russian 76.2-mm field gun, of which considerable numbers mast have been captured. This was the first heavy antitank gun under the control of German ground forces.*** The antitank armament of airborne troops had been considerably strengthened by the introduction of a new tapered-bore gun, the 42-mm Pak 41, which tapers to 28 mm at the muzzle. The 50-mm tank gun used in 1941 was replaced by the long-barrelled 50-mm Kw.K 39 based on the very successful 50-mm Pak 38. An improved 20-mm gun, the Kw.K 38, had been provided for light tanks and armored cars, though later models of some of these have the 50-mm Kw.K 39.

The tables below show the remarkable change in the hitting power of their armament. The guns listed under 1939 were those then in use; those under 1941 and 1942 first appeared in these respective years.

(a) Antitank Guns

1939 37-mm Pak (2,500 f/s)

1941 37-mm Pak (obsolescent)
28-mm Pz.B 41 (4,580 f/s)
47-mm Pak (t) (2,540 f/s) (Czech)
50-mm Pak 38 (2,700 f/s)

1942 37-mm Pak (obsolete)
42-mm Pak 41 (4,500 f/s)
50-mm Pak 38 (2,700 f/s)
76.2-mm Pak 36 (r) (2,200 f/s) (Russian)
75-mm Pak 97/38 (2,100 f/s) (French)
75-mm Pak 40 (2,800 f/s)
75-mm Pak 41 (4,000 f/s)

(b) Tank Guns

1939 20-mm Kw.K 30 (2,600 f/s)
37-mm Kw.K (2,500 f/s)
75-mm Kw.K (1,350 f/s)

1941 20-mm Kw.K 30 (2,600 f/s)
50-mm Kw.K (2,500 f/s)

1942 20-mm Kw.K 38 (2,600 f/s)
50-mm Kw.K 39 (2,700 f/s)
75-mm Kw.K 40 (2,400 f/s)
88-mm Kw.K 36 (2,600 f/s)
75-mm Kw.K 41 (4,000 f/s)

  1939         1941         1942

AP shell AP shell A.P.C.* shell

HE shell A.P.C.B.C.** shell
    (1.25% HE) A.P.C.B.C. shell
    (.31% HE)

AP 40 shot AP 40 shot

HE shell HE hollow charge shell

HE shell

* Armor-piercing capped with ballistic cap (British abbreviation).
** Armor-piercing capped (British abbreviation).

c. Comment on Latest Developments

(1) Antitank Guns

It is quite clear that since 1939 a very great effort has been made to bring into service an efficient antitank gun for every type of combat unit. Even the airborne and parachute troops have had special provision made for them in two light tapered-bore weapons. Most important of all, the Army is now no longer dependent on the GAF for its heavy antitank weapon.

The Army had to obtain from the GAF, on loan, Flak units armed with the 88-mm gun, because it was the only gun in the German service with the requisite performance. The gun crews were GAF personnel, the equipment was not designed to an Army specification, and whether they were made available or not depended in some cases on the personality of the two commanders involved. The GAF for their part has had undoubtedly to suffer pressure from time to time with a view to their releasing Flak units to the Army, and to the employment of these units in a purely AT role to the detriment of AA defense, mainly a GAF responsibility. However, the multi-purpose AA/AT weapons were retained.

The Army must have insisted on having its main antitank weapons produced to its own specification and organized as an integral part of the Army. They now have the 75-mm Pak 40, which weighs about 1 3/4 tons in action as against almost 5 tons for the 88-mm, has the same performance against armor up to 2,500 yards as the 88-mm, can be produced with greater ease, and will be manned by Army crews. In the 75-mm Pak 41, which also weighs about 1 3/4 tons, they have a weapon which will give them performance adequate to defeat, under European fighting conditions (i.e., up to 1,500 yards), any homogeneous armor not thicker than 100 mm, and correspondingly greater thickness at shorter range.

As originally produced, the 75-mm Pak 40 only had a muzzle velocity of 2,400 to 2,500 f/s, and it seemed as if a still more powerful weapon must be developed. Now, however, this gun has been modified; a muzzle velocity of about 2,800 f/s is obtained, and armor-piercing performance is up to that of the 88-mm Flak 36. Therefore, this weapon, along with the 75-mm Pak 41, provides a very powerful combination for all ranges up to 2,500 yards. The Germans may well decide to leave occasional super-heavy tasks to the divisional 105-mm guns and the 105-mm Flak of the GAF. This should not be taken as meaning that they will not proceed with the development of a still heavier antitank gun, but rather that production will probably for the present year, be concentrated on the 75-mm equipment. Any heavier antitank gun may well take the form of an improved 88-mm multi-purpose gun with higher muzzle velocity and a suitable field mounting. (Sketchy reports of an 88-mm Flak 41 much more powerful than the Flak 36 are now starting to come in.)

(2) Tank Guns

Since 1939 a radical change of policy is evident. The 1939 tanks, insofar as gun-power was concerned, could barely fight against the French tanks. The short-barreled 75-mm gun in the PzKw 4 was intended primarily as a close-support gun. Even today it is being used in that role, and has recently been mounted in some PzKw 3 tanks and 8-wheeled armored cars. It should be noted that German tanks have always carried a considerable amount of HE. The killing of soft-skinned targets and antitank guns is always a consideration in their policy.

In 1942 the PzKw 3 and PzKw 4 were rearmed with high-performance long-barreled guns, the 50-mm Kw.K 39 and the 75-mm Kw.K 40, respectively.

These two new guns, together with the 75-mm Kw.K 41 (tapered bore), and the 88-mm Kw.K 36, suggest an interesting line of policy. The demand from the German Army in Africa was undoubtedly for a gun throwing a heavy projectile and keeping its penetration performance up over 2,000 to 2,500 yards. This appears to have been met by the provision of the 88-mm Kw.K 36 mounted on the PzKw 6.

It is doubtful whether the Germans would accept desert conditions, in which so small a proportion of their forces were engaged, as a basis for their major weapon-production program. They are more likely to base this on Russian and European conditions. This seems to have led them to the 75-mm Kw.K 41, a lighter gun with a shorter and lighter (16 1/2-lb) round, but with an armor-piercing performance markedly superior to the 88-mm at any range below 1,500 yards.

The performance of the 75-mm Kw.K 40 is not as good as that of the 88-mm Kw.K 36 at any range, but it is probable that having here a good gun, they will aim at improving its performance.

(3) Ammunition

There has been a marked tendency in the past year to improve the anti-armor performance of AP projectiles, first by reducing the HE capacity of the heavier AP shell, and second by the continued development of high velocity shot with tungsten carbide core. This suggests that a compromise armor-piercing explosive projectile is not acceptable now that substantial thickness of armor has to be dealt with. The latest design of the 75-mm A.P.C.B.C. projectiles has so low an HE capacity as to suggest that this projectile has been included because their troops have become used to a shell that will burst inside the tank, and sudden elimination of the base fuze and explosive feature might worry them. In other words, the Germans are for practical purposes using shot for the attack of thick armor, and retain for every weapon HE for the attack of soft-skinned targets.

It also seems clear that they have been expecting the Allies to go to face-hardened armor, or else they decided some time ago that a piercing cap so improves the performance against any type of armor that the extra production time is justified, since there are now no uncapped AP projectiles in production for anything above 20-mm caliber.

It is a fact that both the 75-mm Pak 40 and Kw.K 40 are provided with hollow-charge in addition to the A.P.C.B.C. and HE, with the expressed intention that the former should not be used for extreme ranges for the reason that it is a low-velocity projectile.

There is every reason to believe that these shells would be of great use against heavily armored pillboxes, armored vehicles, and tanks, because of the "cavity charge" effect.

* Tapers to 20 mm at the muzzle.
** Abbreviation for "Panzerbüchse" literally "antitank rifle."
*** Practically all German antiaircraft units belong to the GAF.