I doudt very much its artillery. The nearest guns are Glasgow and Edinburgh and you would be quicker going to Warcop or Otterburn than go up North.
Its more than likely the usual arse covering for smoolies (lighting flares) etc.
If its weekends only it will mostly be TA and they tend not to do moving live fire exercise at weekends only on annual camps after a weeks build up training. And you need 5km splash behind and 1 km ricochet to the sides which they wouldn't be able to get.
They already have a mortar range at Fort George but I suppose they want somewhere for the heavy mortars.
Suppose it could be anti-tank but realistically they don't fire them very often in training as they cost so much.
My money is on some clueless Captain putting together training order and has over stepped his knowledge base. More than likely after being fed utter bollocks by Lossie who are the parent controlling command for the area.