True and that’s one of the reasons why JS-2 was never used in tank to tank combat. Low rate of fire and limited ammo capacity.
I have read accounts of JS-2s in tank to tank fights with the Germans on the Baltic front in late 44/early 45. The Soviets approved the 122mm gun for the JS-2 because during tests, it punched holes in the front glacis of a Panther at 2000 meters. The Soviets only built 3800 JS-2 from the end of 43 through mid 45.