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A sectioned British World War I 18 pounder Shrapnel round displayed at the Canadian War Museum, Ottawa

Shrapnel shells were anti-personnel artillery munitions which carried a large number of individual bullets close to the target and then ejected them to allow them to continue along the shell's trajectory and strike the target individually. They relied almost entirely on the shell's velocity for their lethality. The munition has been obsolete since the end of World War I for anti-personnel use, when it was superseded by high-explosive shells for that role. The functioning and principles behind Shrapnel shells are totally different from high-explosive shell fragmentation. Shrapnel is named after Major-General Henry Shrapnel (1761–1842), an English artillery officer, whose experiments, initially conducted in his own time and at his own expense, culminated in the design and development of a new type of artillery shell.

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Development of shrapnel shell

This engraving shows a 12-pounder U.S. Shrapnel Shell ca. 1865. It is fitted with a Borman fuze, In the cutaway view, the dark grey is the wall of the shell, the medium grey is sulphur resin, the light grey are the musket balls, and the black is the bursting charge.

In 1784 Lieutenant Shrapnel of the Royal Artillery began developing an anti-personnel weapon. At the time artillery could use "canister shot" to defend themselves from infantry or cavalry attack, which involved loading a tin or canvas container filled with small iron or lead balls instead of the usual cannonball. When fired, the container burst open during passage through the bore or at the muzzle, giving the effect of an oversized shotgun shell. At ranges of up to 300 m canister shot was still highly lethal, though at this range the shots’ density was much lower, making a hit on a human target less likely. At longer ranges, solid shot or the common shell — a hollow cast iron sphere filled with black powder — was used, although with more of a concussive than a fragmentation effect, as the pieces of the shell were very large and sparse in number.

Shrapnel's innovation was to combine the multi-projectile shotgun effect of canister shot, with a time fuze to open the cannister and disperse the bullets it contained at some distance along the cannister's trajectory from the gun. His shell was a hollow cast-iron sphere filled with a mixture of balls and powder, with a crude time fuze. If the fuze was set correctly then the shell would break open, either in front or above the intended target, releasing its contents (of musket balls). The shrapnel balls would carry on with the "remaining velocity" of the shell. In addition to a denser pattern of musket balls, the retained velocity could be higher as well, since the shrapnel shell as a whole would likely have a higher ballistic coefficient than the individual musket balls (see external ballistics).

The explosive charge in the shell was to be just enough to break the casing rather than scatter the shot in all directions. As such his invention increased the effective range of canister shot from 300 to about 1100 m.

He called his device 'spherical case shot', but in time it came to be called after him; a position formalised in 1852 by the British Government.

Initial designs suffered from the potentially catastrophic problem that friction between the shot and black powder during the high acceleration down the gun bore could sometimes cause premature ignition of the powder. Various solutions were tried, with limited if any success. However, in 1852 Colonel Boxer proposed using a diaphram to separate the bullets from the bursting charge, this proved successful and was adopted the following year. As a buffer to prevent lead shot deforming, a resin was used as a packing material between the shot. A useful side effect of using the resin was that the combustion also gave a visual reference upon the shell bursting, as the resin shattered into a cloud of dust.

British artillery adoption

Original Shrapnel design (left), and Boxer design of May 1852 which avoided premature explosions (right)
1870s cast-iron RML 16-pounder "Boxer" shrapnel shell showing limited space for bullets
Forged steel shrapnel shells for BL 5 inch gun with bursting charge in base (left), and in nose (right) for comparison, 1886

It took until 1803 for the British artillery to adopt the shrapnel shell (as "spherical case"), albeit with great enthusiasm when it did. Henry Shrapnel was promoted to Major in the same year. The first recorded use of shapnel by the British was in 1804 against the Dutch at Fort Amsterdam in Surinam.[1] The Duke of Wellington's armies used it from 1808 in the Peninsular War and at the Battle of Waterloo, and he wrote admiringly of its effectiveness.

The design was improved by Captain E M Boxer RA in the 1840-1850s and crossed over when cylindrical shells for rifled guns were introduced. Lieutenant-Colonel Boxer adapted his design in 1864[2] to produce shrapnel shells for the new rifled muzzle-loader (RML) guns : the walls were of thick cast iron, but the gunpowder charge was now in the shell base with a tube running through the centre of the shell to convey the ignition flash from the time fuze in the nose to the gunpowder charge in the base. The powder charge both shattered the cast iron shell wall and liberated the bullets.[3] The broken shell wall continued mainly forward but had little destructive effect. The system had major limitations: the thickness of the iron shell walls limited the available carrying capacity for bullets but provided little destructive capability, and the tube through the centre similarly reduced available space for bullets.[4]

In the 1870s William Armstrong provided a design with the bursting charge in the head and the shell wall made of steel and hence much thinner than previous cast-iron shrapnel shell walls. While the thinner shell wall and absence of a central tube allowed the shell to carry far more bullets, it had the disadvantage that the bursting charge separated the bullets from the shell casing by firing the case forward and at the same time slowing the bullets down as they were ejected through the base of the shell casing, rather than increasing their velocity. Britain adopted this solution for several smaller calibres (below 6-inch) [4] but by World War I few if any such shells remained.

The final shrapnel shell design, adopted in the 1880s, bore little similarity to Henry Shrapnel's original design other than its spherical bullets and time fuze. It used a much thinner forged steel shell case with a timer fuze in the nose and a tube running through the centre to convey the ignition flash to a gunpowder bursting charge in the shell base. The use of steel allowed the shell wall to be made much thinner and hence allow space for many more bullets. It also withstood the force of the powder charge without shattering, so that the bullets were fired forward out of the shell case with increased velocity, much like a shotgun. This is the design that came to be adopted by all countries and was in standard use when World War I began in 1914. During the 1880s, when both the old cast-iron and modern forged-steel shrapnel shell designs were in British service, British ordnance manuals referred to the older cast-iron design as "Boxer shrapnel", apparently to differentiate it from the modern steel design.[3]

The modern thin-walled forged-steel design made feasible shrapnel shells for howitzers, which had a much lower velocity than field guns, by using a larger gunpowder charge to accelerate the bullets forward on bursting.[5] The ideal shrapnel design would have had a timer fuze in the shell base to avoid the need for a central tube, but this was not technically feasible due to the need to manually adjust the fuze before firing, and was in any case rejected from an early date by the British due to risk of premature ignition and irregular action.[5]

World War I era

Labelled diagram of WWI shrapnel round
Trajectory and pattern of US 3-inch (76 mm) Shrapnel shell of WWI era
Bursting action
US, Russian, German, French & British WWI Shrapnel rounds compared
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Technical considerations

The size of shrapnel balls in World War I was based on two considerations. One was the premise that a projectile energy of 58 foot-pounds force (79 J) (US Army calculation)[6] to 60 foot-pounds force (81 J) (British calculation)[7] was required to disable an enemy soldier. At the velocity of a typical World War I 3-inch (76 mm) field gun shell after travelling 6,000 yards (5,500 m), plus the additional velocity from the shrapnel bursting charge (about 150 - 200 feet per second), this was the minimum energy of a single half-inch lead-antimony ball of approximately 170 grains (11 g), or 41-42 balls = 1 pound. Hence this was a typical field gun shrapnel bullet size. For larger guns which had lower velocities, correspondingly larger balls were used so that each individual ball was lethal.

The other factor was the trajectory. The shrapnel bullets were typically lethal for about 300 yards from normal field guns and over 400 yards from heavy field guns. To make maximum use of these distances a flat trajectory and hence high velocity gun was required. The pattern in Europe was that the armies with higher velocity guns tended to use heavier bullets because they could afford to have less bullets per shell. [8]

The important points to note about shrapnel shells and bullets in their final stage of development in World War I are :

  • They used the property of carrying power, whereby if two projectiles are fired with the same velocity, then the heavier one goes further. Bullets packed into a heavier carrier shell went further than they would individually.
  • The shell body itself was not lethal : its sole function was to transport the bullets to the target, and it fell to the ground intact after the bullets were released.
  • They depended almost entirely on the shell's velocity for their lethality : there was no lateral explosive effect.

Tactical use

During the initial stages of World War I, shrapnel was widely used by all sides as an anti-personnel weapon. It was the only type of shell available for British field guns (13-pounder and 18-pounder). Shrapnel was effective against troops in the open, particularly massed infantry (advancing or withdrawing). However, the onset of trench warfare from late 1914 led to most armies decreasing their use of shrapnel in favour of high-explosive. Britain continued to use a high percentage of shrapnel shells. New tactical roles included cutting barbed wire and providing "creeping barrages" to both screen its own attacking troops and suppressing the enemy defenders to prevent them from shooting at their attackers.

In a creeping barrage fire was 'lifted' from one 'line' to the next as the attackers advanced. These lines were typically 100 yds apart and the lifts were typically 4 minutes apart. Lifting meant that time fuzes settings had to be changed. The attackers tried to keep as close as possible (as little as 25 yards sometimes) to the bursting shrapnel so as to be on top of the enemy trenches when fire lifted beyond them, and before then enemy could get back to their parapets.

Advantages

While shrapnel made no impression on trenches and other earthworks, it remained the favoured weapon of the British (at least) to support their infantry assaults by suppressing the enemy infantry and preventing them from manning their trench parapets. It was less hazardous to the assaulting British infantry than high explosives - as long as their own shrapnel burst above or ahead of them, attackers were safe from its effects, whereas high-explosive shells bursting short are potentially lethal within 100 yards or more in any direction. Shrapnel being non-cratering was advantageous in an assault, as craters made the ground more difficult to cross, although they also provided firing positions for infantry. Shrapnel was also useful against counter-attacks, working parties and any other troops in the open.

Shrapnel provided a useful "screening" effect from the smoke of the black-powder bursting charge when the British used it in "creeping barrages".

Disadvantages

Shrapnel was only effective in cutting the barbed wire entanglements in no man's land if the conditions were correct, the angle of descent had to be flat to maximise the number of bullets going through the entanglements, and this limited the effective range. Bullets had limited destructive effect and were stopped by sandbags, so troops behind protection or in bunkers were generally safe.

A shrapnel shell was more expensive than a high-explosive one and required higher grade steel for the shell body. They were also harder to use correctly because getting the correct fuze running time was critical in order to burst the shell in the right place. This required considerable skill by the observation officer when engaging moving targets.

An added complication was that the actual fuze running time was affected by the meteorological conditions, with the variation in gun muzzle velocity being an added complication. However, the British use fuze indicators at each gun that determined the correct fuze running time (length) corrected for muzzle velocity.

Replacement by High-explosive shell

With the advent of relatively insensitive high explosives which could be used as the filling for shells, it was found that the casing of a properly designed high explosive shell fragmented effectively. For example, the detonation of an average 105 mm shell produces several thousand high velocity (1,000 to 1,500 m/s) fragments, a lethal (at very close range) blast overpressure and, if a surface or sub-surface burst, a useful cratering and anti-materiel effect — all in a munition much less complex to make than the later versions of the shrapnel shell. However, this fragmentation was often lost when shells penetrated soft ground and because some fragments went in all directions it was a hazard to assaulting troops.

Variations

One item of note is the 'Universal Shell', a type of field gun shell developed by Krupp of Germany in the early 1900s. This shell could function as either a shrapnel shell or high explosive projectile. The shell had a modified fuze, and instead of resin as the packing between the shrapnel balls TNT was used. When a timed fuze was set the shell functioned as a shrapnel round, ejecting the balls and igniting (not detonating) the TNT, giving a visible puff of black smoke. When allowed to impact the TNT filling would detonate, so becoming a high explosive shell with a very large amount of low velocity fragmentation and a milder blast. Due to its complexity it was dropped in favour of the simple high explosive shell.

During World War I the UK also used shrapnel pattern shells to carry 'pots' instead of 'bullets'. These were incendiary shells with 7 pots[9] using a thermit compound.

When World War I began the United States also had what it referred to as the "Ehrhardt High-Explosive Shrapnel" in its inventory.[10] It appears to be similar to the German design, with bullets embedded in TNT rather than resin, together with a quantity of explosive in the shell nose. Douglas Hamilton mentions this shell type in passing, as "not as common as other types" in his comprehensive treatises on manufacturing Shrapnel[11] and High Explosive shells[12] of 1915 and 1916, but gives no manufacturing details. Nor does Ethan Viall in 1917[13]. Hence the US appears to have ceased its manufacture early in the war, presumably based on the experience of other combatants.

World War II era

By World War II shrapnel shells, in the strict sense of the word, fell out of use, the last recorded use of shrapnel being 60 pdr shells fired in Burma in 1943. A new shrapnel shell, Mk 3D a steamlined shell had been developed for 60 pdr in the early 1930s, it contained 760 bullets of 41/lb size. There was some use of shrapnel by the British in the campaigns in East and North East Africa at the beginning of the war where 18-pdr and 4.5-in (114 mm) Howitzers were used. In 1945 the British conducted successful trials with shrapnel shells fuzed with VT. However, shrapnel was not developed for any of the post World War I guns.

Vietnam era

Although not strictly shrapnel, a 1960s weapons project produced splintex shells for 90 and 106 mm RCLs and for 105 mm Howitzer where it was called 'Beehive'. Unlike the shrapnel shells’ balls, the splintex shell contained flechettes. The result was the 105 mm M546 APERS-T, first used in the Vietnam War in 1966. The shell consisted of approximately 8,000 half gram flechettes, these arranged in five tiers, a time fuse, body shearing detonators, central flash tube, smokeless propellant charge with a dye marker contained in the base and tracer element. The functioning of the shell was as follows; the time fuse fires, flash sent down the flash tube, shearing detonators fire, and the forward body splits into four pieces, body and first four tiers dispersed by the projectile's spin, last tier and visual marker by the powder charge. The flechettes spread, mainly due to spin, from the point of burst in an ever widening cone along the projectile's previous trajectory prior to burst. The round is a highly effective anti-personnel weapon — soldiers report that after beehive rounds were fired during an over-run attack, many enemy dead had their hands nailed to the wooden stocks of their rifles, and these dead could be dragged to mass graves by the rifle — but complex to make. It is said that the name beehive was given to the munition type due to the noise of the flechettes moving through the air resembling that of a swarm of angry bees.

Modern era

Soviet shell of 125 mm for tanks

Though shrapnel rounds are now rarely used, apart from the beehive munitions, there are other modern rounds, that use, or have used the shrapnel principle. The DM 111 20 mm cannon round used for close range air defense, the flechette filled 40 mm HVCC (40 x 53 mm HV grenade), the 35 mm cannon (35 × 228 mm) AHEAD ammunition (152 x 3.3 g tungsten cylinders), RWM Schweiz 30 × 173 mm Air-Bursting munition, 5-Inch Shotgun Projectile (KE-ET) and possibly many more. Also many modern armies have canister shot ammunition for tank and artillery guns, the XM1028 round for the 120 mm M256 tank gun being one example (approx 1150 tungsten balls at 1400 m/s).

At least some Anti-Ballistic Missiles (ABMs) use shrapnel-like warhead instead of the more common blast/fragmentation (blast/frag) type. As with a blast/frag warhead, the use of this type of warhead does not require a direct body-on-body impact, so greatly reducing tracking and steering accuracy requirements.

At a predetermined distance from the incoming re-entry vehicle (RV) the warhead releases, in the case of the ABM warhead by an explosive expulsion charge, an array of mainly rod-like sub-projectiles into the RV's flight path.

Unlike a blast/frag warhead, the expulsion charge is only needed to release the sub-projectiles from the main warhead, not to accelerate them to high velocity. The velocity required to penetrate the RV's casing comes from the high terminal velocity of the warhead, similar to the shrapnel shell's principle.

The reason for the use of this type of warhead and not a blast/frag is that the fragments produced by a blast/frag warhead cannot guarantee penetration of the RV's casing. By using rod like sub-projectiles, a much greater thickness of material can be penetrated, greatly increasing the potential for disruption of the incoming RV.

The Starstreak missile uses a similar system, with three metal darts splitting from the missile prior to impact.

Gallery of images

See also

Notes

  1. ^ Hogg pg. 180
  2. ^ Marshall, 1920
  3. ^ a b "The action of Boxer-shrapnel is well known. The fuze fires the primer, which conveys the flash down the pipe to the bursting charge, the explosion of which breaks up the shell, and liberates the balls". Treatise on Ammunition 1887, page 216
  4. ^ a b "Treatise on Ammunition", 4th Edition 1887, pages 203-205
  5. ^ a b Treatise on Ammunition 1887, page 205
  6. ^ Lt-Col. Ormond M Lissak, Ordnance and Gunnery. A Text-Book. New York: John Wiley, 1915. Page 446
  7. ^ Treatise on Ammunition, 10th Edition, 1915. War Office, UK. Page 173.
  8. ^ Bethel pg. 124
  9. ^ Hogg pg. 173
  10. ^ E.L. Gruber, "Notes on the 3 inch gun materiel and field artillery equipment". New Haven Print. Co., 1917
  11. ^ Douglas T Hamilton, "Shrapnel Shell Manufacture. A Comprehensive Treatise". New York: Industrial Press, 1915
  12. ^ Douglas T Hamilton, "High-explosive shell manufacture; a comprehensive treatise". New York: Industrial Press, 1916
  13. ^ Ethan Viall, "United States artillery ammunition; 3 to 6 in. shrapnel shells, 3 to 6 in. high explosive shells and their cartridge cases". New York, McGraw-Hill book company, 1917.

References

External links


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