Wow - Mortar looks great! Does it have smoke ammo?
I believe small mortars like these were mostly used for suppressive fire, as their shells could not be counted on to inflict any heavy casualties on the enemy. Unlike the 155+mm artillery modelled in the game; now that was the major killer in WW2.
Although I'm no expert on the issue, a 50mm mortar round would have about the same, or a bit more, explosive force as a grenade (judging by the size of the shell). You wouldn't really count on it to destroy any structure, even wooden, or do any serious damage to infantry in good cover.
Please correct me if I'm wrong. I have played a lot of tactical wargames (SP series) and know a 50mm mortar does f*ck all damage to enemy forces, except give them suppression if pounded long enough.