During World War I armored vehicles (tanks) and fortifications began to be widely used, creating the need for ammunition specifically to defeat armored targets. Of course, that led to better armor, and the need for more advanced armor-piercing ammunition.
Early designs were simply solid steel projectiles very similar to the traditional shell shapes to penetrate armor. Hardened projectiles with explosive charges were also used.
Higher velocity guns and projectiles were developed to achieve greater penetration.
Later designs included “shaped charge” designs where a copper cone in the projectile focuses all the energy of an explosion into a very small blast area, so the blast will penetrate even very thick armor.
Most recently, hardened penetrators made of tungsten or depleted uranium fired at extremely high velocity are used to penetrate armor. These are fired in large caliber guns with “discarding sabots” for the high velocity and use fins or cones to stabilize the penetrator in flight.
When an armored target is penetrated, the resulting fragments or explosive blast will usually ignite any fuel or ammunition in a target, causing it to burn and kill the crew even though the outside hulk may only show a small hole.
37-85 "ONE POUNDER" 1918
The 37mm Hotchkiss “one pounder” was developed in the 1880s, but continued in service through World War I, and was used against the primitive tanks when the first appeared on the battlefield.
WW1 37mm portable cannon M1916
.50 CALIBER AP, API, APIT
(Armor Piercing; Armor Piercing Incendiary, Armor Piercing Incendiary Tracer)
used in the .50 caliber Machine Guns designed by
John M. Browning’s .50 caliber M2 Machine gun on ground mount
.50 caliber Browning for aircraft use
20MM AP 1944
One of many different types of 20mm armor piercing ammunition used in cannons mounted on aircraft, vehicles, or on ships as anti-aircraft guns.
Some of the 20mm cartridge types [image courtesy of Tony Williams]
20mm Oerlikon guns on a U.S. Battleship
40MM BOFORS AP (Armor Piercing) M81
Although the Bofors gun was mainly an anti-aircraft gun, it also had AP ammunition for use against surface targets.
40mm Bofors single mount on a PT Boat in the Pacific in WW2
40mm Bofors quad mount on a battleship
90MM M318A1 AP (Armor Piercing)
Among the last of the armor piercing solid projectiles made of hardened steel for punching through armor by brute force. This has a blunt nose, but a pointed aluminum nose cap for better ballistics, with a muzzle velocity of 3,000 feet per second. The 90mm gun was used in M47 and M48 tanks and in tank destroyers, and on artillery carriages.
90mm anti-tank gun
M48 Patton tank with 90mm gun
105MM APDS-T (Armor Piercing, Discarding Sabot-Tracer) M392A2
The “new” generation of armor piercing munitions use a slender, dart-like projectile made of tungsten or depleted uranium, fired from a large caliber gun using a “sabot” while in the gun barrel, peeling off the projectile after it leaves the barrel. Although much lighter than traditional solid AP projectiles, their high muzzle velocity (4,850 feet per second!) still allows penetration of very thick armor. The 105mm gun is used in the M48 and M60 series of tanks.
M60 Tank with 105mm gun
120MM TPCSDS-T (Target Practice Cone Stabilized Discarding Sabot Tracer) M865
The TPCSDS-T cartridge is another variation of the discarding sabot design The projectile is cone stabilized (instead of using fins) for training use with a maximum range much less that the combat versions.
The 120mm gun is used in the M1 Abrams tank.
M1A1 Abrams tank with 120mm gun
NAVY 3 INCH ARMOR PIERCING (APCBC-T)
(Armor Piercing, Capped, Ballistic Capped-Tracer)
MARK 29 MOD 2
This is a pre-World War II design, with a thick steel body, and a hardened steel cap for greater armor penetration. For better ballistics, a hollow aluminum ballistic cap is attached.
Base plug, fuze and explosive filler removed but you can see into the cavity where they fit. Yellow painted nose indicates it was originally loaded with Composition D explosive (since removed). The white band with red dots indicates it had a red tracer element.
During WW2 the 3"/50 slow fire gun was main battery for the Destroyer Escorts and also used to arm merchant ships, and sometimes as secondary battery aboard larger vessels. In the post-WW2 era the rapid fire 3"/50 mounts replaced the 40mm as the main (only) guns aboard amphibious and auxiliary ships. AP ammunition would have been fired only for anti-ship use, while other types were used for anti-aircraft and gunfire support roles.
Cutaway view showing ballistic cap, hardened cap and base fuse and tracer
Twin 3”/50 rapid fire mount on USS Plymouth Rock (LSD-29)
SHAPED CHARGE WEAPONS:
2.36 inch- WWII BAZOOKA ROCKET
3.5 inch- KOREAN WAR BAZOOKA ROCKET
Using a rocket motor to propel the projectile instead of firing from a gun eliminated the need for a gun weighing several thousand pounds, and replaced it with a “Bazooka” rocket launcher weighing less than 20 pounds that could be carried by one soldier. However, the Bazookas only had a range of about 200 yards.
Shaped charges use a cone in the front of the charge so that when it is exploded, the energy of the explosion is directed straight forward instead of bursting out in all directions. A shaped charge can penetrate several inches of armor plate, and the melted fragments of steel entering the inside of a tank will usually ignite fuel or ammunition to totally destroy the target.
The 2.36” Bazooka was used late in World War 2, but the light weight of its warhead made it ineffective against more heavily armored tanks.
The 3.5” Bazooka
was adopted in 1950 and rushed to
2.36” bazooka at left, and with the 3.5” bazooka at right
90MM RECOILLESS RIFLE
M371 HEAT (High Explosive Anti-Tank)
This weapon combined the armor-penetrating effectiveness of the shaped charge warhead with greater range and flatter trajectory than the Bazooka, at a considerable weight saving compared to conventional artillery.
recoilless rifle fires the projectile out the front of the barrel, but the
breech end has holes allowing a huge amount of gas pressure to escape to the
rear. The mass of the gas blasting out
the back is equal to the mass of the projectile leaving the front, so there is
no recoil in the barrel itself. (Remember
90mm Recoilless Rifle in
90MM TANK GUN HEAT-T
M431 HEAT-T (High Explosive Anti-Tank, Tracer) (Experimental)
This has a “stand-off spike” to hold the piezoelectric nose cap which upon impact activates the base detonating fuze. The fuse detonates the explosive charge which is shaped into a piercing jet by the copper cone in the front of the projectile. An aluminum “chamber” seals the rear of the body, holding the fuze and attaching the boom and fins with the tracer element, and the nylon rotating band. These were used in the M47 and M48 Patton tanks, and the M56 “Scorpion” anti-tank vehicle.
This uses tail fins for stability in flight, as the long spike on the nose makes it unstable when fired if it depended only on the spin imparted by the rifling in the barrel of the gun.
Developing complex ammunition requires many tests and improvements. This design started with the “Test 300” projectile, Experimental version 1 (“T300E1”) and went through “T300E59” before being adopted as the M431 for mass production. The example here is the “T300E53T” fairly close to the final version.
This round was professionally sectioned or “cut away” as a training aid.
M56 “Scorpion” Anti-tank gun