You know, that single kills does not count alone?^^
Kill heal+ forward retread base with 1 mortarpit for example.
Also don't forget the mortarpit hits the units first --> HP are away, so other untis can kill the troups easy. And yes your sniper did his job. Min 4 he was on the field. The mortar when? 15, 20 min?
Too it is possible to tell for the Soviet mortar and t70 isn't it?
Protection of mortars, easy task? They won't destroy tanks, and infantry close won't kill