The 152-mm 2S18 "Pat-S" self-propelled artillery system is being upgraded on the modified chassis of the BMP-3 infantry fighting vehicle. This was reported in Kurganmashzavod, part of the High-Precision Complexes of Rostec State Corporation, on May 20.
"The SPG is being upgraded on the basis of a modified BMP-3 chassis. These vehicles, equipped with a 120-millimeter gun (experimental design work "Vienna") and a 152-millimeter gun, can significantly increase the efficiency of motorized rifle units, "the company told RIA Novosti.
2S18 "Pat-S" is an experimental 152-mm howitzer developed in 1980 at the Kurgan Machine-building Plant.
2S31 Vena/Vienna (pic related) 120-mm entered service with Azerbaijan and Venezuela around 2010, the Russian army never showed any interest in the vehicle.
It is clear that the Russians have taken a liking to front-line artillery, as with roaming mortar, etc.
It is a good way of adapting the Russian taste for artillery to the particularities of the conflict. I imagine that this vehicle will cover that role of indirect fire from a closed position, the same as the T-55 or T-62, as do the normal BMP-3s from what you see in videos.