It is really a very big blast, like an artillery blast like you say. I was given three opportunities to throw hand grenades during my conscription training.

First one was in a purpose-built field, where we were hunkered down in a concrete hole and threw the frag-grenade onto gravel.

The second was when were having an exercise of storming a machinegun-nest on top of a small ridge in the forest. So first we move by leapfrog (a combat pair) firing, then climbed a small ridge and threw over a live frag-grenade on to the "machinegun-nest".

Third time was when we were doing a urban combat exercise. In the middle of the forest they had a roofless building with several rooms, again purpose-built for training with live grenades, with dust floors. We were given two grenades each, one which was a chock grenade ( not flash , again doing the exercise as a combat pair. Really big blasts.