Shooting the War

Artillery Guns of the WWII

Running parallel with this unfolding story of piercing projectiles was the development of the hollow-charge principle into a viable weapon. This illustrates the adaptation of a well-documented scientific phenomenon to a weapon of war: almost 200 years ago a Norwegian engineer had observed that hollowing out the face of an explosive charge made it cut deeper into rock when blasting. In the 1880s an American experimenter, Monroe, found that when firing guncotton slabs against armour plate, the initials ‘USN’ engraved in the guncotton reproduced themselves in mirror-like form in the face of the armour plate. From his observations and reports the phenomenon became known as the ‘Monroe Effect’ and was a scientific curiosity for many years. Just before the First World War one or two inventors toyed with the idea of employing this effect in mines and torpedoes, but since no one really understood why it did what it did, it was difficult to engineer the idea into a practical form.
Just before the Second World War broke out, a Swiss consortium approached the British government to offer a ‘new and powerful explosive’ for anti-tank use—at a high price. The inventors refused to divulge any information until cash was forthcoming, but were prepared to demonstrate their projectile being fired. An astute observer from the Research Department of Woolwich Arsenal went to Switzerland to watch the firing; being a well-read expert on ammunition development and history, he realised that what he was watching was not a new and powerful explosive so much as a practical application of the Monroe Effect. Upon his return to Woolwich he duly reported this, and, since it appeared that the Monroe Effect could be made to work, research immediately began into applying it to a light anti-tank grenade which the infantry soldier could fire from his rifle. Before the outbreak of war, this ‘68 Grenade’ had been perfected and was in production, and carries the distinction of being the first weapon ever to reach the hands of troops which relied on the Monroe Effect, or as it came to be known, the Hollow-Charge Principle.
What is this Hollow-Charge Principle? Put simply, it consists of forming the forward surface of the shell’s explosive charge into a cone or hemisphere and then lining this with a thin metal liner. The shell is then fitted with a suitably shaped nose, for ballistic effect and also to give the vital ’stand-off’ distance. This is the distance from the target—a matter of a few inches—at which the explosive must be detonated in order for the hollow charge to work effectively. On detonating the explosive at its rear end, the detonation wave exerts an immense pressure on the metal of the liner; the cone shape virtually’focusses’the explosive energy and causes the metal of the liner to be shaped into a jet of finely-divided metal and explosive gas, shooting toward the target at speeds of up to 20,000 feet per second. The stand-off distance is necessary in order to allow this jet to form and accelerate. When the jet strikes the target plate, the pressure exerted is so great as to blast a hole through the armour, blowing splinters of metal from the inside and permitting the white-hot jet to pass into the tank where it will set fire to fuel or ammunition, and, of course, kill or injure the crew.
The great virtue of the hollow-charge shell is that its performance is always the same, irrespective of the velocity at which it strikes. Even if the shell were standing still when detonated, the penetration would be the same. Because of this, it could be fired from guns too small to fire the large cartridges needed to give the necessary velocity to normal piercing projectiles. As soon as the 68 Grenade was seen to be successful, design began on other hollow-charge projectiles. A great deal of work went into producing one for the 25-pounder, though in the end it was never issued, since the AP shot issued for that gun was quite satisfactory and there was no real need for a hollow-charge shell. Then came a request from India to produce an anti-tank projectile for the 3.7-inch Pack Howitzer, the modern version of Kipling’s immortal ’screw-gun’. This gun, a small and portable weapon, could not be made to fire a piercing projectile at anything like the velocity needed to defeat even Japanese tanks, and a hollow-charge shell was designed and placed in production. The same shell was used in the 95-mm howitzer, an abortive infantry support gun which never saw service as a towed weapon, though it was employed as a self-propelled support weapon by the Royal Marines in Normandy and by the Armoured Corps.
By 1944, though, sufficient basic research had been done into this principle for it to be seen that a spinning shell was not the ideal method of employing hollow charges, since the spin tended to spread the jet out and give poor penetration. Finned projectiles were more effective, and consequently no more artillery shells were designed around the hollow charge; it was extensively employed, instead, for infantry weapons such as the PIAT, the Bazooka, and a variety of rifle grenades.
The Germans, and later the Russians, embraced the hollow-charge shell wholeheartedly. The Germans began issuing shell in late 1940 and eventually almost every German field and tank weapon had a hollow-charge shell, thus giving every gun or howitzer an anti-tank capability. Indeed, so short were the Germans of anti-tank guns after the Russian invasion got under way, that they hastily collected up all the French army’s 75-mm guns and assembled hundreds of them on to redundant anti-tank gun carriages of German design. A hollow-charge shell was produced and these makeshift weapons were deployed in Russia to stem the advancing Soviet tanks until 75-mm and 88-mm anti-tank guns were in sufficient supply. Judging from appearances, the Soviet hollow-charge shells were developed as virtual copies of German designs which had been captured.
In addition to artillery shell Germany also used the principle for infantry weapons such as the Panzerfaust, rifle grenades, and even a small shell which could be fired from a signal pistol. They also employed the principle in an ingenious attempt to prolong the life of the prewar 37-mm anti-tank gun, whose piercing projectile was, by 1942, no longer effective against current tanks. A large hollow-charge bomb was fitted with a hollow tail carrying fins; within this tail was a stick which fitted snugly into the barrel of the 37-mm gun, allowing the tail and fins to slide over the barrel. A blank cartridge completed the outfit, and this was used to fire the stick bomb to ranges of 300 to 400 yards. The bomb’s warhead was about 6 inches in diameter and carried about 8 pounds of explosive, giving a devastating effect at the target. In all fairness, it must be pointed out that Lieutenant-Colonel Blacker, inventor of the PIAT and the `Black Bombard’ of Home Guard fame, had proposed a similar 60-pound stick bomb in 1940, to be fired from the 25-pounder, but the idea was turned down on the grounds that it might lead to misemployment of the gun as a purely anti-tank weapon. (This misemployment theme was not confined to the British side: many German Flak commanders bewailed the loss of their valuable 88-mm Flak guns as they were whittled away to provide anti-tank defences.)
The third subject is the application of new principles to gun design. The first of these to be unveiled was the taper-bore antitank gun, which has already been touched upon. This was the child of a German engineer called Gerlich, who, advocating his principle of attaining high velocity without attracting any buyers, had been stumping the world for several years. He was briefly employed by both the US War Department and the British War Office at various times, but his ideas on improving shoulder arms were felt to be impractical. He eventually settled in Germany and saw his idea accepted as an anti-tank weapon. The 28/21-mm came first, then a 42/30-mm and finally a 75/50-mm. Unfortunately, the lack of tungsten carbide for the special projectiles spelled the demise of these weapons, but experiments continued with coned bores and coned muzzle-adapters for guns of various calibres up to as large as 280-mm, in order to boost velocity and range. These were intended to use high-explosive shells, which were more practical in the larger calibres, though the development of a shell which would stand up to being squeezed down the gun barrel was no easy task.
The second, and more widespread, new line of thought was the recoilless gun. Like most weapon ideas, there was nothing really new about it: Commander Davis of the US Navy had produced a recoilless (RCL for short) gun during the First World War which was adopted by Britain as an anti-Zeppelin aircraft weapon. The virtue of an RCL gun is that by having no recoil one needs no complicated hydraulic buffer system to absorb the firing shock: one need only make the gun-carriage strong enough to take the weight of the gun, instead of being strong enough to withstand being fired from—an ideal state of affairs for an aircraft weapon, particularly in the stick-and-string era. Davis’s idea is worth looking at, although outside our time scale, since it is the classic recoilless weapon. He simply provided the gun with two barrels, one pointing forward which fired a normal shell, and one pointing rearward which fired an identical weight of grease and buckshot. When the central cartridge was fired the shell and countershot departed at equal speed in opposite directions and cancelled each other’s recoil. From this it can be seen that if you make the countershot (say) one-fifth of the weight of the shell and fire it out at five times the speed, then the gun will still be in balance. Taking this idea to its logical conclusion one finishes up firing out of the back of the gun a fast, light stream of gas, still balancing the recoil since the weight times speed of the gas is the same as the (greater) weight times (slower) speed of the shell.
Cutting down the recoil
This was the principle which the Germans revealed in Crete when their troops appeared armed with a 75-mm RCL gun. The shell was the standard 75-mm shell, but the cartridge case had a frangible plastic base which held for long enough to allow pressure to build up and start the shell moving, then blew out through a hole in the breech-block, releasing the balancing stream of gas. The all-up weight of the gun, on its ex-machine gun tripod, was only 320 pounds, whereas the weight of the standard 75-mm field gun was about 11/2 tons—no mean saving for airborne carriage. A 105-mm version soon followed, weighing 855 pounds as opposed to the 105-mm 1E FH18’s 4,312 pounds, and many more developments began in this field to provide light weapons for mountain troops and infantry, particularly for anti-tank use. (It ought perhaps to be pointed out that the Panzerfaust was in fact a recoilless gun, and not, as generally supposed, a rocket launcher). Eventually RCL guns of up to 380-mm calibre were under development, including many for slinging beneath aircraft to carry artillery aloft for the battle against the Allied bombers, but none of these came to fruition.

n Britain, the RCL gun development during the war is a scarcely-known story of one man’s persistence. Sir Denis Burney, airship designer and prolific inventor-engineer, began to be interested in the recoilless principle early in the war. In order to prove his theories he converted a four-bore gun into a recoilless weapon and proceeded to fire it from the shoulder with ease; it must have been the world’s most comfortable duck gun. Having proved his point he proceeded to design a series of RCL guns ranging from 20-mm to 8-inch calibre. In addition to designing the guns, he expanded his theories and designed special ammunition to take advantage of the ballistic peculiarities of the weapon. He argued that since the rearward blast was taking place, the pressure within the gun would be less than with a conventional type, and the shell would be subjected to a more steady thrust. In which case it would be possible to make shells with thinner walls, which would carry greater charges of explosive than previously possible. He then went further, and reasoned that, since the shell walls were thin, if the shell were to be filled with the then new plastic explosive, it would spread on to the surface of the target like butter; a fuse fitted in the base of the shell would then detonate this plaster and blast in the target. His envisaged target was either the concrete emplacements of the European coast, or the palm-reinforced Japanese bunker, and he called his shell the Mal I buster’.
In 1944 his designs were accepted and a 3.45-inch (the same calibre as the 25-pounder) shoulder-fired gun, a 3.7-inch towed gun, a 95-mm towed howitzer, and a 7.2-inch towed howitzer were prepared for production. The 95-mm was also jeep-mounted—the first application of what has since become a standard method of carrying these guns. The 7.2-inch soon fell by the wayside, since it had been intended solely as a means of defeating the Atlantic Wall emplacements, but other weapons were found to do all that was needed. The 3.45-inch was intended as an infantry weapon in the jungle, enabling one man to carry what was virtually a 25-pounder punch on his shoulder. The 3.7-inch was proposed as the future infantry anti-tank weapon, and the 95-mm was contemplated as the airborne field gun to replace the US 75-mm howitzer and the 25-pounder. However, before the guns were produced in sufficient quantity for issue, the war came to an end; some 3.45-inch and 3.7-inch guns were issued to selected infantry units to obtain their reaction to RCL guns as a general thing, and the 95-mm was abandoned altogether.
The principal difference between the Burney guns and the German type was that the Burneys had much longer barrels, and used cartridge cases which, instead of the plastic blow-out base, used many perforations in the sidewall to release the gas into a surrounding chamber, from whence it was passed back to a number of vents around the breech.
Concurrently with Burney’s work in Britain, American designers began on similar weapons. A 105-mm howitzer T-9 was developed on similar lines to the German 105-mm, having a blow-out base to the cartridge. Another team developed 57-mm and 75-mm weapons which used perforated cases similar to the Burney pattern but having more and smaller holes, and also had the shell driving band pre-engraved in order to reduce the pressure inside the gun. Both these latter weapons were accepted for service early in 1945, saw service with the US Army in the Pacific theatre, and remained in service for many years. A third team, this time under the auspices of the National Research and Development Council, developed a 4.2-inch RCL mortar, an unlikely-sounding weapon which so as to be able to fire direct at the target at low angles, carried a small rocket on the nose of the shell to push it down the barrel’and fire the propelling cartridge in the usual mortar fashion. Due to the blast of the rearward jet, it could only be fired at low elevations; there was a certain amount of enthusiasm for this weapon but it never entered service.
Perhaps the best summing up of all wartime development on RCL weapons was made in a wartime report: ‘Undoubtedly a number of effective recoilless weapons have been developed, but they are being accepted with reserve, and will only be considered as supplementary to older and more orthodox weapons which have proved their accuracy and reliability in service.’
There is, unfortunately, no space here to delve into more recondite stories of research and development: the British 13.5-inch gun linered-down to 8-inch calibre which, fired from Dover, reached a range of over 100,000 yards; the British and American development of flying artillery, which culminated in the mounting of a 32-pounder anti-tank gun in a Mosquito; the German V-3 multiple-chamber gun which was intended to shell London; the American 36-inch mortar ‘Little David’, designed to batter Japanese strong-points; the German rocket-assisted and ramjet-assisted heavy artillery shells which promised vast increases in range; or the Anglo-American development of the electronic proximity fuse which proved the answer to both ‘Doodlebugs’ and kamikaze pilots. These and similar stories may only interest the specialist, but they, together with what has been written here, serve to illustrate the incredible range of inventions brought into play in the war waged between the designers and inventors of each side, each endeavouring to get one step ahead of the other, if only temporarily.

The German Super-Guns of the WWII

The German super-guns
The heaviest field equipments seen during the war were the German self-propelled howitzers generically known as ‘Karl Morsers’. These were of two calibres, 540-mm and 600-mm, mounted on the same type of carriage. Six carriages were made and the exact disposition of barrels between them is in some doubt; the carriages were numbered I to VI; Vehicle V was captured by the US 1st Army and found to have a 540-mm barrel, yet photographs captured later showed this same carriage to have a 600-mm barrel. It is probably safe to assume that three of each calibre were made. The date of introduction is also a little vague, but it seems fairly certain that the 600-mm version was introduced in 1942 and the 540-mm in 1944.
The carriage of ‘Karl’ was a simple rectangular box, divided into three compartments. The first held the Mercedes-Benz engine and transmission; the second carried the gun; and the third held the carriage raising and lowering gear. After driving into position on its tracks the engine was used to drive the lowering gear, which rotated the anchorages of the suspension torsion bars so as to allow the chassis to be lowered to the ground until the suspension and track were relieved of the weight. For long-distance moves the gun and recoil system were removed from the carriage, dismantled, and loaded on to spec,a -,a e•s, the carriage was then winched on to a special tank-transpor-er. For very long distances the complete gun and carriage assembly could be slung between two railway flat wagons by means of special trusses.
In the use of railway artillery Germany virtually had the field to herself. This class of weapon is really the prerogative of the Continental nation with a well-developed rail system by which it can readily deploy them to any front. In contrast, Britain and the USA, while possessing railway guns. used them solely as mobile coast defence units, since the problem of transporting two or three hundred tons of railway mounting across the Channel was not a trick to be undertaken lightly. Indeed, the British and American weapons were almost entirely relics of the First World War which had been in mothballs. 1940 saw a few more mountings hastily cobbled together from available spares and hurried to cover the Channel, just as in similar fashion American guns were mobilised and deployed in 1941. In 1944 reports from France indicated that heavy railway artillery might be of use in demolishing strongpoints to be expected in the final assault in Germany, and designs were hastily prepared by the Americans for a number of 16-inch guns, but within a few weeks it was seen that heavy artillery of this class had been rendered superfluous by the quality and quantity of air support available, and the demand was cancelled.
The German army had a vast range of railway guns from 150-mm upwards, but two were really outstanding and deserve closer examination. The first was the 28-cm K5(E)—Kanone, Model 5, Eisenbahnlafette —which became their standard super-heavy railway gun and was probably the finest design of its k;nd in the world. The basic arithmetic and paperwork had been done in the late 1920s and early 1930s, and work began on the gun in 1934. (It is worth noting that every German railway gun was designed and built by Krupp— Rheinmettal did design two, but they were never made.) First, a 150-mm barrel was produced for tests; it had been decided that to obtain the great range demanded, a conventionally rifled barrel was out of the question. A design was prepared with 12 deep grooves and having a shell carrying 12 ribs, or splines, to match. The theory behind this was that the engraving of a conventional copper driving band on the shell gave rise to very high pressure in the gun chamber; by using the spline and groove method to spin the shell, this resistance was removed, and the shell would step off more smartly, allowing a bigger propelling charge to be used without over-straining the gun. The 150-mm test barrel proved that the theory was right, and a full-calibre 280-mm barrel was built.
The mounting was a simple box-girder assembly carried on two six-axle bogies, with the front bogie slung so as to allow the front of the box-girder to be swung across it for aiming the gun. For large angles the whole weapon was mounted on a special portable turntable built at the end of a short spur of track laid at the desired firing point. Each gun was supplied with a special train which included wagons for carrying the turntable, light-antiaircraft guns for local defence, air-conditioned ammunition wagons, living quarters and kitchen for the gunners, and flat wagons to carry their entitlement of motor transport.
By 1940 eight of these complete equipments were in service, and production continued throughout the war, 25 being built in all. The German gunners called them ‘Slim Bertha’, but to the Allies in Italy one at least became famous as ‘Anzio Annie’.
With the 561-pound pre-rifled shell the gun could reach to 68,000 yards. A rocket-assisted shell was later developed which increased this range, with a certain loss of accuracy, to 94,000 yards. Finally, the Peenembride Research Establishment designed a 300-pound dart-like projectile which was fired from a special 310-mm smooth-bore barrel and which ranged to 170,000 yards. Although coming too late for general issue, these ‘PeenemOnde Arrow Shells’ were issued for troop trials in the field, and some were fired against the US 3rd Army at ranges of about 70 miles.
The second railway gun, ‘Gustav’, was the biggest gun the world has ever seen —the Krupp-designed 800-mm Kanone. The idea was conceived in 1937 of a pair of super-guns; they were of quite conventional design, except for their immense size. Too large to be moved in one piece, they were transported piecemeal in special trains and assembled at the selected sites by travelling cranes. When assembled, the mounting straddled two sets of standard-gauge rails, with 80 wheels taking the 1,350-ton weight. An armour or concrete-piercing shell of 7 tons was propelled by a 13/4-ton charge to a range of 23 miles, or a 5-ton high-explosive shell to 29 miles. The first equipment, ‘Gustav’, was proved at the Rugenwalde range in March 1943, in Hitler’s presence. The only record of its use was at the siege of Sebastopol; the gun was sited at Bakhchisary and fired some 30 to 40 rounds. One shot is recorded as having penetrated through 100 feet of earth to destroy a Soviet ammunition dump at Severnaya Bay. The subsquent history of the gun is unknown (it was presumably captured by the Red Army).
The second equipment, ‘Dora’. so far as is known, never left the proving ground, though what happened to it at the end of the war is a minor mystery (some ammunition and a spare barrel were found at Krupp’s proof establishment at Meppen near the Dutch border).
The detachment necessary to man. maintain, and give local protection to Gustav was 4,120 men strong. commanded by a major-general. The actual fire-control and operation of the gun demanded a colonel and 500 men, and the construction or dismantling of the weapon took between four and six weeks. A long-range ‘PeenemOnde Arrow Shell’ was developed for Gustay. but, so far as is known, was never fired. This was to weigh 2.200 pounds and range to 100 miles. There was also a proposition to mount a 520-mm gun on the same carriage to fire rocket-assisted shells and ‘PeenemOnde Arrow Shells’ to a range of 118 miles for cross-channel bombardment, but this never got past the drawing-board.
If it is accepted that it is not a good idea to tamper with a good gun design in the middle of a war, then the only way to render the gun more effective is to improve the ammunition, and this technique was frequently adopted during the war. And in no field is this seen to greater effect than in the battle against the tank. The reason for this is fairly self-evident: personnel targets remain more or less the same—once the anti-personnel projectile is perfected it can stay as it is. On the other hand, once a new anti-tank projectile appears, it is only a matter of time before the enemy put thicker armour on his tanks.
At the outbreak of war there were two types of anti-tank projectile: the armour-piercing (AP) shot, and the AP shell. The difference is basic. Shot are solid, with no explosive filling, and rely purely on their speed to smash through the armour and do damage inside the tank by their impact, the fragments of plate they knock off during penetration, and their own effect when they penetrate the plate and bounce around inside the tank. AP shells, on the other hand, have a small cavity filled with high explosive and are fitted with a fuse in the base. The shell penetrates, similarly to shot, by brute force, but the fuse is activated by the impact and, after a short delay to allow the shell to pass through the plate and enter the tank, the explosive is detonated, shattering the shell into fragments and adding to the shot-like damage already caused. On paper the shell is the better proposition, since there is the bonus of the explosive filling. But paper figures tend to be deceptive, and in fact the shot is probably the more practical projectile, because the high-explosive (HE) cavity weakens the shell, and the fuse is precariously supported against the hammer-blow of impact. Britain held firmly to the shot theory for anti-tank work, though many years of experience in producing AP shells for naval use was available. Several other nations preferred AP shell, bewitched by the HE bonus.
Most of the belligerents entered the war with a plain shot or shell and relied on throwing it hard enough to penetrate the opposing tanks. So long as the target was relatively lightly armoured this was successful; but, naturally, each side began to increase armour thickness on each succeeding generation of tank. The quick answer to this was to increase the gun charge or even the calibre, and thus throw the projectile harder, but there comes a time when the impact is too much for the projectile, and instead of piercing, it merely shatters on the outside of the target without doing any damage.
The answer to this was to protect the tip of the shot or shell with a softer cap, which tended to spread the impact stresses over the shoulders of the projectile, instead of concentrating them into the tip. This preserved the piercing action to higher velocities, and the gun was again winning the battle. The next move belonged to the tank designers who made their armour thicker, and so it went on until the projectile was once more shattering, cap or no cap. At this point the projectile designers were faced with a new problem: if it was futile to throw the projectile harder, might it not be possible to throw a harder projectile? And what was harder than an armour-piercing projectile? Tungsten carbide, a diamond-hard alloy, provided an answer, but it was about one-and-a-half times as heavy as steel, so that it could not easily be made into a projectile. Furthermore, it was expensive and in short supply.
The first application of tungsten to an anti-tank projectile was by the German army in their 28-mm Schwere Panzerbuchse 41, a weapon with a unique tapered barrel. The shot consisted of a small core of tungsten carbide held in a light alloy casing of 28-mm calibre. As the shot was fired down the gun barrel, so the calibre diminished and the light alloy casing was ground down, until it emerged as a 21-mm shot. This squeezing enhanced the velocity and changed the ratio of shot diameter to weight. The velocity reached was 4,000 feet per second, and, on impact with the target, the hardness of the core was impervious to impact shock and penetrated successfully.
About the same time—late 1940—a similar idea had been put forward by a Mr Janacek, a Czechoslovakian weapon designer working in England. While his idea was still under consideration, a specimen of the German weapon was captured in North Africa and flown home for trials: the idea was seen to be feasible. The British version was in the form of a taper-bore adapter to be fitted to the existing 2-pounder gun, together with a special tungsten-cored shot, known under the code name of ‘Littlejohn’, an Anglicised version of Janacek. The advantage here was that the adapter could be removed to permit firing normal explosive shells, but could be refitted quickly for the special shot, whereas the German design required a special pattern of high-explosive shell to be developed, a difficult feat in such a small calibre. The ‘Littlejohn’ attachment and its shot were not used in towed artillery, since by the time they were ready for service the anti-tank units were armed with 6-pounders, but it was used on 2-pounder and American 37-mm guns mounted in armoured cars.
To use tungsten in a conventional gun, a different approach was needed. The first attempt, for the 6-pounder, was the ‘AP Composite Rigid’ (APCR) shot, a tungsten core mounted in an alloy sheath of approximately the same dimensions as the conventional steel shot for the gun. By virtue of its light alloy content the APCR shot was somewhat lighter and thus had a higher velocity when fired. Unfortunately the ratio of weight-to-diameter was unfavourable, giving a poor ballistic coefficient or ‘carrying power’, and while the short-range performance was impressive, the velocity soon dropped, and at ranges over 1,000 yards, steel shot was just as good, sometimes better. Some German weapons were also provided with the same type of projectile, and one was designed for use in the Soviet 76.2-mm field gun which the Germans captured in large numbers and converted into an anti-tank gun. Unfortunately for them, by early 1942 the shortage of tungsten in Germany began to be felt, and in the middle of that year a ban was placed on the use of tungsten in ammunition; what scarce supplies there were had been earmarked for machine tool production, not for throwing about the Russian steppes. After strong remonstrations, the 5-cm Pak 38 anti-tank gun was specifically exempted from this ban, since at that time it was the only weapon capable of stopping a Russian T-34 tank, provided it was supplied with tungsten-cored shot.
Although the 6-pounder APCR shot seemed reasonably successful, it was not the ideal answer. The ideal, in fact, sounded ridiculous: what was wanted was a shot which in the barrel was large-calibre and light, so as to pick up speed quickly and leave the gun at high velocity, but which outside the barrel should be small in diameter and heavy, so as to have good ‘carrying power’ and keep up its high velocity for a long range. These two conflicting requirements were fused into one projectile by two British designers, Permutter and Coppock, of the Armaments Research Department. Even before the 6-pounder had received its APCR shot they were at work, and in March 1944 their ‘AP Discarding Sabot’ shot was provided for the 6-pounder. In this design, the tungsten core is contained in a streamlined steel sheath or sub-projectile; this in turn is carried in a light-alloy framework or ’sabot’ of the full gun calibre. On firing, this sabot holds the sub-projectile centralised in the bore and gives the whole thing the combination of light weight and large area which is wanted for velocity. But firing actually ‘unlocks’ the sabot, and as the shot leaves the gun muzzle, so the sabot is thrown clear, allowing the sub-projectile to race to the target at velocities of the order of 3,000 feet per second. Now, since the sub-projectile’s sheath is virtually a skin round the tungsten core, it follows that the weight is high in relation to the cross-section—the ideal condition for good carrying power and thus long-range performance. A similar projectile for the 17-pounder followed in September 1944, and one was under development for the 20-pounder tank gun when the war ended.

German, French, British, American and Russian Guns of the WWII

As with the tanks, so with the guns: the artillery designers of the
Second World War found themselves caught up in a ceaseless race
to outmatch the ever-improving enemy defences. Ian Hogg shows how
this affected the gunners’ war, and how it resulted in the artillery
revolution of greater ranges, mobility and fire control.

A thorough discussion of the history and development of every artillery weapon used in the Second World War would need several volumes, for the sheer size of the subjects is incredible; the German forces alone disposed over 200 land service weapons in 51 different calibres, without considering experimental models. Britain and America between them fielded about 100 artillery weapons, again not counting experimental models but only those which found their way into the hands of troops. Instead of trying to catalogue every weapon used, therefore, this section merely outlines the principal features of the research which developed during the war, and also brings to light one or two of the more unusual and less well-known weapons which were produced.
There are three main subjects to be explored:
•    The routine improvement of weapons, in order to bring them into line with changing tactics and concepts of employment or to counter improvements in enemy defences;
•    The improvements in ammunition introduced to step up the performance of existing weapons;
•    The application of hitherto untried scientific principles.
In many cases these topics tend to overlap, but rather than try to develop a chronological story with these three aspects jumbled together, it is best to consider them as separate fields.
First, routine improvement. A good example of this in action is the history of the celebrated German 88-mm Flak Gun. This was originally conceived in the late 1920s by Krupp designers attached to the Bofors Company in Sweden. When in 1931 they returned to Essen with the design, the political climate seemed right. A prototype was built in 1932; and due to thorough paperwork it was an immediate success and was issued in 1933 as the 8.8-cm Flak Model 18. It should be stressed, in view of the exaggerated tales which became current in later years, that there was nothing unorthodox about this weapon at all—it was simply a good, sound, conventional anti-aircraft gun. It was taken to Spain by the Kondor Legion during the Civil War and tested in action; its potentialities as an anti-tank gun were also seen, though not advertised. This experience showed that there were a few weak points in the design and as a result, minor modifications were made in the mounting to improve stability and facilitate mass-production. This modified version became known as the Flak 36. In the following year an improved sighting and fire-control system was fitted, and the gun became the Flak Model 37. The 36 and 37 remained in service throughout the Second World War, being used in their primary role as an anti-aircraft gun; as an anti-tank gun, when fitted with shields and direct-fire sights; fitted to coastal craft and U-boats; used as a coast defence gun; and even mounted on a 121/2-ton half-track as a self-propelled gun (though this was not one of its most successful applications).
By early 1939 though, in spite of its excellence, it became obvious that bombers were going to fly faster and higher than before, and the gun’s performance would have to be improved. And so in 1939 Rheinmettal-Borsig were given a contract for an improved model, to be known as the Flak 41. Prototype trials began in 1941 and it was found that the gun, although a most efficient design, had a lot of teething troubles which were going to take time to eliminate. Since no one else had a contract for the gun, the Luftwaffe (which was responsible for Germany’s anti-aircraft defences) was forced to use it or else do without. Consequently the next year saw a great deal of effort thrown in and by March 1943 the first issues were made.
The Flak 41, as finally produced, was a considerable improvement over the 18, 36, and 37. By using a turntable to carry the gun, instead of the more usual pedestal mounting, a much lower silhouette was achieved. The muzzle velocity and ceiling were both improved by adopting a more powerful cartridge, and the stability in action was excellent. The only fly in the ointment was the difficult extraction of the fired cartridge case, which is a flaw of major proportions in a quick-firing anti-aircraft gun. Different designs of barrel were produced in an effort to overcome the trouble, and a special brass cartridge case was developed; but none of these palliatives made much impression and the gun was never the success it might have been.
Some time after Rheinmettal had received their contract, a similar specification had been given to Krupp. Their development, sometimes referred to as the Flak 42, became more and more entangled with their concurrent development of 88-mm tank and anti-tank guns in the hopes of producing a family of weapons which would use interchangeable parts and common ammunition. Before the Krupp version had got off the drawing board, the Luftwaffe was demanding more performance than the design could produce, and in February 1943, not without a certain amount of relief, one feels, Krupp dropped the Flak 42 to concentrate on the tank and anti-tank weapons.

While the 88 shows an example of improvement of a particular calibre, the more common approach was to improve a particular class of weapon by raising the calibre; most anti-tank weapons display this technique. The British army began the war with a 2-pounder; followed it by a 6-pounder and then a 17-pounder; and finally had a 32-pounder in preparation when the war ended, having toyed briefly with a possible 55-pounder. America began with a 37-mm, took over the British 6-pounder and called it the 57-mm; then moved to a 3-inch based on a redundant anti-aircraft gun; then a 90-mm, also based on an AA gun, and was working on a 105-mm when the war ended. Germany also began with a 37-mm and progressed through 28, 42, 50, 75 and 88-mm to arrive at a 128-mm as the war closed.
All these series show steady progression in conventional guns, ally intended to beat the forthcoming increases in enemy armour. However, the flaw in this system becomes apparent on looking at the British 32-pounder or the German 12.8-cm Pak 44— bigger calibres may mean a bigger punch, but they invariably mean bigger guns as well, and this means more weight to move about. This is a considerable drawback for an anti-tank gun which usually has to be emplaced by manpower, and certainly the 32-pounder was too big for its task; even had the war continued, it is doubtful whether it would have been accepted into service.
Anti-aircraft guns tend to show a similar pattern among all nations, always striving to extract more ceiling and greater velocity; the increased ceiling meant that higher-flying aircraft could be engaged, while higher velocity meant a shorter time between firing the gun and the shell arriving at the target, and hence less room for error in the prediction of the target’s position at the time of the shell’s arrival. The two groups of anti-aircraft weapons in common use were the light guns, such as the German 37-mm and the British and US-employed Bofors 40-mm, and the heavy guns, such as the German 88, 105, and 128-mm guns, the British 3.7-inch, 4.5-inch, and 5.25-inch guns, and the American 90-mm, 105-mm, and 120-mm types. The light guns relied on throwing up a heavy volume of fire at a high rate, to counter the low-flying attacker. The heavies fired at slower rates, threw heavier shells, and had higher ceilings to deal with the high-level bomber. But strangely enough, all the combatants had a gap in their defences, which lay between the maximum ceiling of the light guns—about 6,000 feet—and the minimum effective ceiling of the heavies—about 10,000 feet. Below this figure the heavy gun could not swing fast enough to follow a fast low flyer. In an endeavour to fill this gap, development took place in both Britain and Germanyto provide a medium AA gun. As far as Britain was concerned, a paramount feature of any weapon proposed in 1940 was to avoid usurping production already hard at work with the more basic weapons needed for simple survival. In view of this, the first question the designers asked themselves was: ‘What existing gun can be worked over to fill the bill?’ After a few false starts the design coalesced around The existing coast artillery 6-pounder gun, the same calibre as the anti-tank gun but using a heavier cartridge and capable of greater range. This was adapted to a twin-barrel mounting on a three-wheeled trailer, and work then began on designing a suitable automatic feed system to get the rate of fire thought necessary, and a fire-control system to put the shells where they were needed. Since the guns were originally designed for hand loading, the adaptation to autofeed turned out to be more difficult than had at first been imagined; then Allied air superiority gave the project less priority; and, in the event, the twin 6-pounder never entered service and Britain never had a medium AA gun.
The German development was not restricted to an existing weapon, since the ‘gap’ had been appreciated before the war, and in 1936 Rheinmettal was given a contract to develop a 50-mm gun. This was eventually introduced in 1940 in limited numbers for an extended troop trial to assess whether such a weapon was desirable and whether the Flak 41, as it was known, would fill the requirement. For a variety of reasons the gun was not a success, but the experience showed that the medium AA gun was needed, and a great deal of thought went into the design of a completely integrated weapon system, probably the first such system to be conceived as a complete entity. It was to comprise a 55-mm automatic gun, with matched radar, predictor, displacement corrector, and full electro-hydraulic remote control of a six-gun battery. By the time all these theories and designs had been put together it was mid-1943, and the production of such a far-reaching concept was so difficult that the war ended before the weapon was completed. To act as a stop-gap, the now-obsolescent 50-mm anti-tank gun was fitted with an automatic loading system, but this idea fell by the wayside, and it is doubtful if any were ever made. All in all, the medium AA gun story is remarkable in the similarity of British and German experience.

In the field artillery world practically all development was simply a matter of improvement on existing designs. No nation in its right mind would attempt a major re-equipment of its standard weapons in.the middle of a war. The British 25-pounder served valiantly, and modifications to meet special demands included the self-propelled ‘Bishop’ (on a Valentine chassis) and ‘Sexton’ (on a: Ram chassis); the Australian-developed ‘Short’ or ‘Baby’ 25-pounder with a truncated barrel, no shield, short trail and castor wheel for easy manoeuvring in the jungle; it was tried as a self-propelled gun (SP) in many vehicles including the Lloyd carrier, which was asking too much of such a light vehicle; it was strapped to the cargo bed of a DUKW for supporting amphibious landings; and it was even considered for the armament of submarines. Similarly, the American 105-mm howitzer was tried in a variety of SP mountings, starting with a half-track, until the Sherman-based M-7 became standardized as the ‘Priest’; it was shortened and placed on a light carriage for use by airborne units; it was mounted in tank turrets as a close support gun; and, like the 25-pounder, mounted on the long-suffering DUKW.
The German 1E FH 18, more or less the equivalent of the 25-pounder and 105 howitzer, suffered similar, though more drastic, changes. First it was given a muzzle brake and a heavier charge with a long-range shell; then in an attempt to reduce the weight, like the ‘Baby 25-pounder’, the barrel and recoil system were mounted on the carriage of the 75-mm Pak 40 anti-tank gun; the wheels were removed and it was dropped bodily into a tank hull to provide an assault gun; it was grafted on to a variety of tracked mountings. But eventually a complete re-design was called for and Rheinmettal was given a contract. Before their offering was ready, the experiences of the Russian Front had shown that certain features were mandatory in the next generation of field guns. Briefly, these were that the gun must have a good anti-tank performance for self-protection; at the same time it ‘iad to be capable of hiding in forests and firing out at high angles: the range had to be at least 8 miles without demanding special ammunition; it had to have all-round traverse, since Soviet partisans c,)uld attack from any direction; and it had to weigh less than 2.200 pounds. Now even today a designer would have a hard time meeting that specification, but in 1943 both Krupp and Skoda rose to the challenge.
The Skoda version, the 10.5-cm 1E FH 43. was most ingenious: the carriage had virtually a normal split trail at the rear. plus another split trail at the front, beneath the barrel. and a firing pedestal beneath the axle. In action, the equipment rested on the two rear trails and the pedestal, and the front trails were laid on the ground to form a cruciform stable platform above which the gun could rotate through 360 degrees, the four legs giving stability at any angle of the barrel. The novelty of this carriage lay in the fact that the two front legs were not rigidly attached to the carriage; to compensate for eneven ground they were permitted to lie at any convenient angle. A hydraulic system was arranged so that slow movement of the legs—as during folding and unfolding to and from the travelling position—was freely permitted. but fast movement—as the firing shock—would cause the legs to lock rigidly to the carriage and give the desired stability.
Krupp, under the same nomenclature, produced two models; one was very similar in general design to Skoda s. though without the hydraulic system, while the other was based on a more or less conventional cruciform platform of the type familiar in AA guns. However, none of the designs, Krupp or Skoda. were ready for production before the war’s end, and only prototypes existed.