Not knowing the dimensions makes it tough.
When rounds are painted blue, that is the international symbol for practice rounds. I doubt if there is any explosives in it. Then again, a can of blue paint would turn me into a liar pretty quick.
I have to agree that it looks like a mortar round, as the tail lacks the skinny spring loaded stabilizing fins and the long burn tube of an RPG.
Hey, there are hundreds of different types of RPG's out there, just look:
or this
or this
You get my drift.
A case of beer says it is a mortar round.
Look at the holes for burn on the tail. Doesn't that mean that the burn is supposed to happen violently and in all directions? You would need a tube to compress that shit and give it direction. MORTAR.
If it had one burn hole in the back and stabilizing fins, it would be a weird and short looking RPG.
It doesn't have any MORTAR collars around the neck, which I would expect to see. Those blast off after firing, don't they?
Help me out, you mortar platoon boys.