First World War Era
Shot and shell used prior to and during World War I were generally cast from special chromium (stainless) steel that was melted in pots. They were forged into shape afterward and then thoroughly annealed, the core bored at the rear and the exterior turned up in a lathe. The projectiles were finished in a similar manner to others described above. The final, or tempering treatment, which gave the required hardness/toughness profile (differential hardening) to the projectile body, was a closely guarded secret.
Shot and shell used prior to and during World War I were generally cast from special chromium (stainless) steel that was melted in pots. They were forged into shape afterward and then thoroughly annealed, the core bored at the rear and the exterior turned up in a lathe. The projectiles were finished in a similar manner to others described above. The final, or tempering treatment, which gave the required hardness/toughness profile (differential hardening) to the projectile body, was a closely guarded secret.
The rear cavity of these projectiles was capable of receiving a small bursting
charge of about 2% of the weight of the complete projectile; when this is used,
the projectile is called a shell, not a shot. The HE filling of the shell,
whether fused or unfused, had a tendency to explode on striking armor in excess
of its ability to perforate.
Second World War
APHE shells for tank guns, although used by
most forces of this period, were not used by the British. The only British APHE
projectile was the Shell AP, Mk1 for the 2 pdr anti-tank gun and this was
dropped as it was found that the fuse tended to separate from the body during
penetration. Even when the fuse didn’t separate and the system functioned
correctly, damage to the interior was little different from the solid shot, and
so did not warrant the additional time and cost of producing a shell version.
APHE projectiles of this period used a bursting charge of about 1-3% of the
weight of the complete projectile, the filling detonated by a rear mounted
delay fuse. The explosive used in APHE projectiles needs to be highly
insensitive to shock to prevent premature detonation. The US forces
normally used the Explosive D, otherwise known as ammonium picrate, for this
purpose. Other combatant forces of the period used various explosives,
suitability desensitized (usually by the use of waxes mixed with the explosive).
Due to the increase in armor thickness during the conflict, the projectiles’ impact velocity had to be increased to ensure perforation. At these higher velocities, the hardened tip of the shot or shell has to be protected from the initial impact shock, or risk shattering. To raise the impact velocity and stop the shattering, they were initially fitted with soft steel penetrating caps. The best performance penetrating caps were not very aerodynamic, so an additional ballistic cap was later fitted to reduce drag. The resulting projectile types were given the names "Armor-Piercing Capped (APC)" and "Armor-Piercing Capped Ballistic Capped (APCBC)".
Early WWII-era uncapped AP projectiles fired from high-velocity guns were able to penetrate about twice their caliber at close range (100 m). At longer ranges (500-1,000 m), this dropped 1.5-1.1 calibers due to the poor ballistic shape and higher drag of the smaller-diameter early projectiles. Later in the conflict, APCBC fired at close range (100 m) from large-caliber, high-velocity guns (75-128 mm) were able to penetrate a much greater thickness of armor in relation to their caliber (2.5 times) and also a greater thickness (2-1.75 times) at longer ranges (1,500-2,000 m).
Due to the increase in armor thickness during the conflict, the projectiles’ impact velocity had to be increased to ensure perforation. At these higher velocities, the hardened tip of the shot or shell has to be protected from the initial impact shock, or risk shattering. To raise the impact velocity and stop the shattering, they were initially fitted with soft steel penetrating caps. The best performance penetrating caps were not very aerodynamic, so an additional ballistic cap was later fitted to reduce drag. The resulting projectile types were given the names "Armor-Piercing Capped (APC)" and "Armor-Piercing Capped Ballistic Capped (APCBC)".
Early WWII-era uncapped AP projectiles fired from high-velocity guns were able to penetrate about twice their caliber at close range (100 m). At longer ranges (500-1,000 m), this dropped 1.5-1.1 calibers due to the poor ballistic shape and higher drag of the smaller-diameter early projectiles. Later in the conflict, APCBC fired at close range (100 m) from large-caliber, high-velocity guns (75-128 mm) were able to penetrate a much greater thickness of armor in relation to their caliber (2.5 times) and also a greater thickness (2-1.75 times) at longer ranges (1,500-2,000 m).
Modern Day
Armor-piercing shells
Armor-piercing shells in the classic form are not common in modern guns, though they may be found in the larger (40-57 mm) weapons, especially those of Russian- or Soviet-era descent. Modern guns instead fire semi-armor-piercing high-explosive (SAPHE) shells, which have less anti-armor capability, but far greater anti-materiel/personnel effects. The modern SAPHE projectiles still have a ballistic cap, hardened body and base fuze, but tend to have a far thinner body material and higher explosive content (4-15%). Common abbreviations for modern AP and SAP shells are: HEI(BF), SAPHE, SAPHEI and SAPHEI-T.
Most modern active protection systems (APS) are unlikely to be able to defeat full-caliber AP rounds fired from a large-caliber tank gun. The APS can defeat the two most common anti-armor projectiles in use today: HEAT and APFSDS. The defeat of HEAT projectiles is accomplished through damage/detonation of the HE filling or damage to the shaped charge liner and/or fusing system, and defeat of APFSDS projectiles is accomplished by inducing yaw/pitch and/or fracturing of the rod. Due to the AP shot/shell's high mass, rigidity, short overall length, and thick body, they are hardly affected by the defeat methods employed by APS systems (fragmentation warheads or projected plates).
Armor-piercing shells in the classic form are not common in modern guns, though they may be found in the larger (40-57 mm) weapons, especially those of Russian- or Soviet-era descent. Modern guns instead fire semi-armor-piercing high-explosive (SAPHE) shells, which have less anti-armor capability, but far greater anti-materiel/personnel effects. The modern SAPHE projectiles still have a ballistic cap, hardened body and base fuze, but tend to have a far thinner body material and higher explosive content (4-15%). Common abbreviations for modern AP and SAP shells are: HEI(BF), SAPHE, SAPHEI and SAPHEI-T.
Most modern active protection systems (APS) are unlikely to be able to defeat full-caliber AP rounds fired from a large-caliber tank gun. The APS can defeat the two most common anti-armor projectiles in use today: HEAT and APFSDS. The defeat of HEAT projectiles is accomplished through damage/detonation of the HE filling or damage to the shaped charge liner and/or fusing system, and defeat of APFSDS projectiles is accomplished by inducing yaw/pitch and/or fracturing of the rod. Due to the AP shot/shell's high mass, rigidity, short overall length, and thick body, they are hardly affected by the defeat methods employed by APS systems (fragmentation warheads or projected plates).
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