Speaking as an 81mm Mortar (former, its an arty weapon now). I don't care how hard he hugs that barrel, the accuracy is gonna go to dog shat. He would be better off to walk up to an enemy with a box of grenades and give 'er!
Its not like shooting the 60mm Mortar in light role with Charge 0 or 1 (ever try a 60 with charge 2 or 3 for kicks? Weapons goes all over the place).
In this case, if they do not mind HE bombs all over the place, give 'er.
Yes I have done field expedient things, sometimes with desirable results and sometimes with minor disaster.