Found a few videos that will help:
Here's one of a hobbyist explaining the basic workings of the rifle grenade. (I actually never knew about the sight that could be attached until this video)
https://www.youtube.com/watch?v=sv7m-jyy7Ng
Here's an video of some people firing a dummy grenade off of it in the desert. It also gives a quick screenshot of an army manual that shows the range of the grenade in different positions. 1-6
https://www.youtube.com/watch?v=vukYdgepSZk
You can see the huge amount of recoil and how cumbersome it is to fire this thing off.
From what I've seen from old footage it was mostly fired with the butt-plate in the dirt like a make shift mortar unless the soldier had to peek over a wall or something to get the shot off.
Hope this helps
