I know, I googled it already, I just think it's a very stupid idea. You'll never be able to aim precisely with such a thing. The recoil with a normal weapon is along the aiming axis, while here it's totally uncontrollable.
Sorry I wasn't meaning to be rude or anything, I guess I just take for granted how periscopes work.
but like _xxx_ link showed, it's really just a pair of mirrors at 45 degrees. Then instead of having the scope run parallel to the barrel I imagine it probably is perpendicular to the barrel. Then if they wanted to get fancy, they could probably put it on an adjustable hing so you could then have it hanging perpendicular below the gun and you can shoot from behind cover over obstacles.
The krummerlauf wasn't a ploy, it was a stopgap solution for the eastern front when the Soviets launched massed infantry charges on tank positions. They hadn't put defensive MGs on their superheavy tank destroyer Ferdinand/Elephant and had to improvise which was by sticking the krummerlauf out of the top hatch and hose the tank off.
Like _xxx_ said, you would need it to have gyroscopes, independent suspension and active correction to be practical. A remote-controlled robot would probably be easier.