[serg3d]

I'm playing russain long campain too.
Don't worry about buying KV and T-34 in 1941 - it's completly historical. They were staple of tank brigades in 1941.
Stalin ordered formation of tank brigades in august, after RKKA Mech Corps were bleeded dry in huge border tank battles.
For example here is 142 tank brigde equipment on the september 1 1941:
KV-1 7
T-34 22
T-26 57 (light tanks of tank brigades vary - could be T-60, BT, T-38, T-40 etc)
AA guns 12
ATG 8
mortars 12
LMG 43
SMG 181
rifles 551

trucks 202
utility vehicles 15
tractors 8
Most actively used were of cause T-34. KV-1 were slow and often couldn't manage to reach fight in time. Light tank were fragile. Tank brigade commanders often complain that the only tanks they really coul use were T-34.