The Ukrainian offensive in the southeast often involves an artillery duel that the Ukrainians must win, or at least survive, before they can continue advancing. While Ukraine has received modern artillery and ammunition from NATO, the Russians have to improvise. One of those improvisations involves using older T-55 and T-62 tanks as mobile artillery that can deliver accurate direct (at targets the gunner can see) or indirect (at more distant targets the gunner cannot see) targets.
The T-62 has proved to be the most effective Russian improvised direct-fire artillery. The T-62 has a 115mm gun, which was the first modern, smoothbore, tank gun used by Russian tanks (or anyone else) and fires the same types of ammunition (high explosive, armor-piercing, and more exotic types) as more modern 125mm tanks. The smaller caliber means 115mm armor-piercing rounds are not quite as effective as the 125mm against the better frontal armor of Ukrainian tanks, but hits on the side or rear armor are still deadly. The 115mm ammo can destroy any lighter armored vehicles. The T-62 carries 40 115mm shells, which have a max range of 4,000 meters, but are most effective at 1,000 meters. Upgraded T-62s weigh 38 tons, compared to 44 tons for the T-72. T-62 max road speed is 50 kilometers an hour while cross-country speed is 40 kilometers an hour. Max range with internal fuel on roads is 650 kilometers and 450 kilometers cross-country. The T-62 anti-tank shells are effective against lighter armored vehicles while its high-explosive shells are very effective against enemy infantry and any buildings or fortifications the enemy infantry may be firing from. Russians no longer use T-62s as tanks, but as assault guns.
The assault gun concept was popular during World War II when the turretless assault guns were developed by the Germans and were considered as an infantry weapon that belonged to the infantry. Russia also adopted the assault gun concept and had great success with their series of turretless assault guns. These included 76mm guns on the SU-76, 122mm on the SU-122, and the 152mm on SU-152 assault guns, plus various types based on the T-34 tank chassis. Towards the end of World War II these were followed by the ISU-122 and ISU-152 on the new IS heavy tank chassis. After World War II, Russia developed the 15-ton ASU-85 with an 85mm gun. This vehicle could be dropped from an aircraft and safely land using parachutes. The 31-ton Su-100 tank destroyer based on a T-34 chassis had a 100mm gun that was effective against armored vehicles as well as infantry, and some are still in service. Nearly 5,000 were built between 1944 and 1950. Many were exported and these are often still used by countries with tiny defense budgets. Russia but several hundred into storage but none of these have showed up in Ukraine
After World War II the assault gun concept was abandoned in favor of tanks as infantry support, but that did not work out as well as expected. Now, the Russians have returned to the assault gun concept by using the elderly T-62 and its 115mm cannon to support infantry. During World War II turretless armored vehicles with large guns were developed for infantry support. Using tanks or self-propelled artillery to replace assault guns after World War II did not work out well in practice. In part that was because the assault gun, during World War II, belonged to the infantry units rather than tank or artillery units. The T-62 assault guns now belong to the infantry even if they did not have an opportunity to train with the infantry before combat.