In the 1950s, the Soviet Union set out to design a new, more powerful anti-tank gun to replace the old 100 mm M-1944 (BS3) anti-tank gun. According to this new approach, a range of powerful ammunition would be developed while maintaining the caliber of the gun, which in turn would have a smooth bore instead of the usual rifled bore. The use of the smooth bore gives greater muzzle velocity to the projectile, which leads to greater penetration power, although also more stability problems. To solve these problems, the Soviets chose to add fins to the penetrating dart, which gave a muzzle velocity of more than 1,500 meters per second, much more than the 900 m/s reached by the armor-piercing discarding sabot (APDS) rounds used until then.Finally, in 1955 the first 100/63mm T-12 (2A19) anti-tank gun was presented. This gun had proven during tests to be capable of penetrating up to 230 mm of armor at a distance of 1,000 meters, enough to destroy any Western tank of that time. The T-12 carried the same carriage as the 85 mm D-48 anti-tank gun, which was too narrow and was a constant source of problems. In fact, the T-12 could not be towed cross-country at more than 15 km/h, since at higher speeds the gun could tip over easily. The piece carried 6 servants, including the driver of the towing truck, and had several sights for direct and indirect fire. For indirect fire it had an S71-40 system equipped with a PG-1M panoramic sight. For daytime direct fire it had an OP4M-40U sight, while for nighttime direct fire it had APN-5-40 or APN-6-40 sights.This gun uses a range of powerful anti-tank ammunition, more than it might initially seem for a gun of only 100mm caliber. It has the APFSDS-T (Tungsten) 3BM-2 round capable of penetrating 230 mm of armor at 500 meters or 180 mm at 2,000 meters, the APFSDS 3BM23 and 3UBM10 rounds capable of penetrating 225 mm at 1,000 meters and the HEAT 3BK16M and 3UBK8 rounds capable of penetrating 400 mm at 1,000 meters. It can also fire the 9K117 Kastet 3UBK10 and 3UBK10M laser-guided projectiles (missiles) capable of penetrating 600mm of armor. Against unarmored targets and infantry the T-12 gun has the high-explosive (HE) 3OF12 and 3OF35 rounds.T-12 gun entered service in 1961 and was distributed among the anti-tank units of the motor rifled and armored divisions. The main mission of these guns was to protect the flanks against enemy counterattacks during rapid advance. The power and range of the new gun allowed the units not to depend on expensive and rarer tank destroyer vehicles for an effective defense, and these vehicles could be used during the attack. In addition, ts light weight of 2.75 tons and its range of 8 km make it ideal for accompanying the infantry during their advance. In 1972, an improved variant called MT-12 Rapira was presented, which had a modified carriage and a new equilibrator among other modifications.This gun was the main towed anti-tank artillery of the Soviet Union and some satellite countries until well into the 80s and it is estimated that the production of T-12 and MT-12 guns reached around 4,000 units, of which many remain in service today, not so much as an anti-tank weapon but as support artillery. Romania and China made their own versions of the T-12 gun, designated A-407 (on the image) and Type 86 respectively. This gun has been used in numerous conflicts such as the Soviet–Afghan War, the Iran–Iraq War or the most recent Syrian civil war, War in Donbas and the 2022 Russian invasion of Ukraine, where some Ukrainians MT-LB tracked carriers have been converted into tank destroyers by installing a T-12/MT-12 gun on the roof.
