Shrapnel is the term originally applied to an anti-personnel artillery shell which carried a large number of individual bullets to the target and then ejected them forwards, relying almost entirely on the shell's velocity for their lethality. Today the term is commonly used to describe the metal fragments and debris thrown out by any exploding object, be it a high explosive (HE) filled shell or a homemade bomb wrapped with nails or steel balls. The functioning and principles behind Shrapnel shells proper were totally different to high-explosive shell fragmentation.
The word shrapnel is derived from the name of Major-General Henry Shrapnel (1761–1842), an English artillery officer, whose experiments, initially conducted on his own time, and at his own expense, culminated in the design and development of a new type of artillery shell.
The term originally referred only to the spherical shot or musket balls dispersed when a shrapnel shell bursts, and this is still the strict technical definition of the term. However, "shrapnel" is now commonly used to describe all types of high-velocity fragments thrown out from an explosion, and does not differentiate among the processes which create them.
For shells, bombs or other munitions, the technical term for these particles is fragments, splinters or shards, fragments being the preferred name in scientific documents on the subject.
Another term which can be used to describe a particle other than a bullet which causes a wound is "bomb fragment" or "bomb shard". These terms also include items which were not part of the original explosive device, but which are propelled as projectiles by the force of the explosive or impact.
Instead of a cannonball, a tin or canvas container filled with small iron or lead balls was loaded. 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 delayed-action fuse to take the effect of canister shot to the enemy at a distance. His shell was a hollow cast-iron sphere filled with a mixture of balls and powder, with a crude time fuse. If the fuse 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. This problem was overcome by placing the powder within a central metal tube, or a separate area within the hollow shell. 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.
It took until 1803 for the British artillery to adopt it, albeit with great enthusiasm when it did. Shrapnel was promoted to Major in the same year. The Duke of Wellington used it beginning in 1808 against Napoleon, including in the Battle of Waterloo, and wrote admiringly of its effectiveness.
The design was improved by Captain E M Boxer RA in the 1840s and crossed over when cylindrical shells for rifled guns were introduced.
The size of shrapnel balls in World War I was based on the premise that a projectile energy of 58 foot-pounds (US) to 60 foot-pounds (British) was required to disable an enemy soldier. At the velocity of a typical World War I field gun shell after travelling , plus the additional velocity from the shrapnel bursting charge, this was the minimum energy of a single half-inch lead-antimony ball of approximately , 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 important points to note about shrapnel shells and bullets in their final stage of development in WWI are :
During the initial stages of World War I, shrapnel was widely used by all sides to attack troops in the open, though trench warfare reduced its use as high explosive shells became the predominant type of 'explosive' shell used. 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. It prevented the Germans manning their trench parapets and was less hazardous to the assaulting British infantry than high explosives. Shrapnel being non-cratering was also advantageous in an assault. Shrapnel was also useful against counter-attacks, working parties and any other troops in the open. However, shrapnel was unable to cut the barbed wire entanglements in no man's land, defeat troops under protection, or destroy positions all of which were required in the preliminary bombardment to an attack.
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. 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. 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 close range) blast overpressure and, if a surface or sub-surface burst, a useful cratering and anti-material effect — all in a munition much less complex to make than the later versions of the shrapnel shell.
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 fuse and instead of resin as the packing between the shrapnel balls, TNT was used. When the fuse was set to time, the fuse functioned in the normal way, ejecting the balls and igniting (not detonating) the TNT, the TNT giving a visual puff of black smoke. In impact mode the TNT filling was detonated, so becoming an high explosive shell with a very large amount of low velocity fragmentation and a milder blast. Again due to its complexity, it was dropped in favour of the simple high explosive shell.
When World War I began the United States also had what it referred to as the "Ehrhardt High-Explosive Shrapnel" in its inventory. 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 and High Explosive shells of 1915 and 1916, but gives no manufacturing details. Nor does Ethan Viall in 1917. Hence the US appears to have ceased its manufacture early in the war, presumably based on the experience of other combatants.
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.