The Soviet Army learned the value of tank-killing, armor-defeating weapons during World War 2 (1939-1945) when it squared off against the might of the Wehrmacht armored divisions. Most of the solutions centered around high-velocity, towed field guns with effective penetrating projectiles and it was this sort of thinking that continued for Soviets into the Cold War period (1947-1991). In 1955 was debuted a new, towed ant-tank gun and this product quickly became the standardized weapon of the Army and other Soviet-aligned nations and foreign allies followed in equipping the type. The MT-12 "Rapira" series was in operation service with Soviet forces up until the latter part of the 1980s but went on to serve a plethora of global operators from Algeria and Armenia to Ukraine and Uzbekistan - many of which continue to field the weapon even today (2017).
The MT-12 has also been recognized by the formal designation of "2A19" and also as the "T-12". The type was taken into service to replace the aging line of 100mm BS-3 series field guns which had been in service since 1944 (World War 2).
At the core of the T-12 design was its chosen 100mm projectile fired from a smoothbore barrel assembly. Compared to the BS-3, the MT-12 was given an all new gun tube and revised two-wheeled carriage to go along with a gun shield - all based on lessons learned from the fighting of World War 2. The barrel measured 63 calibers which made up a good portion of the overall length of 31 feet for the complete weapon system. The gun shield held a three-sided, angled appearance and was sloped for basic ballistics protection - a vision port being cut-out from the upper left side for the aimer. The carriage was of a traditional two-wheeled, rubber-tired design with tow arms located towards the rear. The wheels were elevated from the ground when the system was made ready-to-fire. The gun mounting hardware allowed for an elevation span of -6 to +20 degrees and traversal of 27-degrees right or left of centerline.
A trained gunnery crew could fire (theoretically) fourteen rounds-per-minute though a four-to-six rpm rate was realistic. The crew numbered six personnel and the gun system required a mover vehicle for long-range travel though the gunnery crew could make due somewhat over very short distances (the complete weapon weighed over 6,000lb).
The MT-12 fired an APFSDS-T ("Armor-Piercing, Fin-Stabilized Discarding Sabot - Tungsten") projectile of 12.5lb at a muzzle velocity of 5,170 feet per second out to a range of 3,300 yards. Since the gun tube of the MT-12 was smoothbore (not rifled), the projectiles required built-in, spring-loaded fins for in-flight stabilization. Penetration at 3,300 yards was 5.5 inches of armor. At 550 yards, the weapon could defeat nearly 10 inches of armor.
Beyond the typical armor-piercing, fin-stabilized round, the weapon supported a HEAT (High-Explosive, Anti-Tank) and HE-FRAG (High-Explosive, FRAGmentation) projectile as well as the 9K117 "Kastet" beam-riding, laser-guided missiles.
The MT-12 "Rapira" was the debut form designation and this was followed by the MT-12R "Ruta" which equipped the RLPK-1 series radar for improved accuracy under smoke conditions. The MT-12K "Kastet" was introduced in 1981 and supported the firing of 9M117 "Kastet" missiles.
Over 6,000 MT-12 guns have been in service with the Soviet Union / Russians. The next largest operator became Ukraine with some 400 units in inventory at one point. Iraq is a former operator of the product and many were lost in the Gulf War of 1991 and the final stock was all destroyed during the 2003 U.S.-led invasion and subsequent occupation. The former nation of Yugoslavia had its MT-12 supply passed on to successor states (mainly Bosnia and Herzegovina as well as Croatia ) following its dissolution.
The A407 marks a locally-designed Romanian model influenced by the MT-12 series. China copied the MT-12 as the Type 73 and the Type 86 is believed to be a sort of related offshoot, also of 100mm caliber