Here the reference to history of creation and history of war of this gun - SU-122:
http://www.bronetehnika.narod.ru/su122/su122.html
http://armour.kiev.ua/Tanks/WWII/SU122/su122.html
In the end of this history it is written (machine translator):
"...
However howitzer SU-122 still remained on arms of samohodno-artillery regiments. In such to a regiment was available 16 SU-122 which up to the beginning of 1944 continued to be used for support of infantry and tanks. However its such application was insufficiently effective because of small initial speed of a shell - 515 km/s - and, hence, small indirect its trajectories. Arriving since August, 1943 in much considerable quantities in armies new SU-85 has quickly replaced the predecessor in the field of fight and nevertheless it is necessary to notice, that capacity of 85-mm of fragmentation shells was insufficient for breaking up of strips of defence of the opponent. Therefore, for example, armoured management of 4th guards tank army in April, 1944 persistently asked the higher organisations to find at least 20 SU-122 as SU-85 were unsuitable for struggle against the strengthened machine-gun points.
... "
I suggest to clean this gun # 030 - 122mm M30 L22 from game and SU-122 before occurrence SU-122-54.