[Suhiir]

When I first when in to the service we were still using M40 106mm recoiless rifles. While they were primarily an anti-tank weapon they did have both flechette and high explosive rounds.
As to using them for indirect fire, well they're not mortars so it's not like you have the backblast going into the ground at your feet or would position them nose-to-tail like the ones in your photo. As long as the backblast has somewhere to go and no one is stupid enough to get behind the weapon it's not really that big a deal.
Remember they can fire a round much, much further then they can accurately hit a point target (like a tank) so it's merely a matter of elevating the weapon and cutting loose in the general direction of the target ... walla ... indirect fire.