At max range, M-42 has 60 penetration. Ostheer's Panzer IV has 180 armor (OKW's has 234). As such, only a third of your shots will penetrate. ...
Hitting the rear is achieved by taking advantage of camo.
First strike bonus probably also provides penetration with accuracy and reload
Damage is buffed from FHQ.
And once more the unit's roles is not counter mediums tanks but light vehicles up to puma/Luch. Any buff the unit receives or vet abilities/bonuses should increase the chance to truck, hit and not be circle strafed from these unit. It should work like a 6 ponder without the penetration and serve as counter to heavy light vehicles/tank strategies from the opponent.
It should not be a substitute for the Zis.