I have tried every weapon, and personally have only had impact effect issues with the Mosin Nagant, scoped or otherwise.
I do have manual bolting enabled, but I don't experience the issue with the Kar, scoped or not.
After about an hour of shooting everything I could think of with the Mosin Nagant, I didn't get a single impact effect on snow, dirt, brick, normal walls, wood floors, rubble, anything.