The following footage shows a MK-19 gunner hammering Taliban positions with grenades as they receive accurate incoming small arms fire.

This footage was previously given to us by the production team for the documentary "Pech River Boys: Tales From Afghanistan" and I highly recommend that you check it out. Watching the whole film will also explain why these troops are leery of poking their heads out of the fortification or too long. The Taliban have the positions ranged and have inflicted casualties on the soldiers.