The US Army used the 50 spotter (M48) chambered semi auto aiming tool mounted on a Howitzer for the same purpose as the russian tank mounted aiming tool.
I have a shellholder rifle chambered in the 50 spotter.
No sniper rifle, but it does a lot of damage to anything that's in the way of the 822 grain big ass hollow point it shoots.
It would make the perfect suppressed weapon, but Cumhole always pisses on anything that makes sense.
SJC
I remember pulling security on a fire base on a mountain top in the middle of nowhere that had a couple 106(?) mm recoils rifles mounted on tripods with a .50 cal rifled barrel piggybacked on top. I asked one of the Arties what the .50 was for and he said they load a .50 cal. bullet with a white phosphorous head on it that fires at the same trajectory as the recoiless rifle and use it as a spotting round. He even fired one off and sure enough about a klick away down in the valley a white puff of smoke drifted up out of the understory. He said that is where the recoils would impact. Base was near Laos and there were tanks about, so it sure seemed like a good idea to me, it was pretty cool.
I don't remember it being as fancy as the one in the picture, more like a barrel with a breech lock.
Robin