2S1 Gozdzik

Looks like it was built on the BMP chassis.

This gun is MT-LB chassis.

The 2S1 Gvozdika (Russian: 2С1 «Гвоздика», "Carnation") is a Soviet self-propelled howitzer based on the MT-LB APC chassis, mounting a 122 mm 2A18 howitzer. "2S1" is its GRAU designation. An alternative Russian designation is SAU-122 but in the Russian Army it is commonly known as Gvozdika. The 2S1 is fully amphibious with very little preparation, and once afloat is propelled by its tracks. A variety of track widths are available to allow the 2S1 to operate in snow or swamp conditions. It is NBC protected and has infra-red night-vision capability.
The first prototype was ready in 1969. The 2S1 entered service with the Soviet Army in the early 1970s and was first seen in public at a Polish Army parade in 1974. The vehicle was deployed in large numbers (72 per tank division, 36 per motorized rifle division). It was designated the M1974 by the U.S. Army and manufactured in Soviet, Polish and Bulgarian state factories.
https://en.wikipedia.org/wiki/2S1_Gvozdika