The Russian lenses made after WW2 should work OK on Leica. If you are having problems with your Leica body focusing various lenses, then it is posssible that your Leica body is in need of calibration. The rangefinder is not so strong that it will stay in adjustment forever. There are web pages on the net that go into precise detail on adjusting your rangefinder. It is not hard, and you do not have to disassemble the camera, just remove a cover screw and a ring around one of the rangefinder windows to get to the adjustments. Get your rangefinder accurate, and you should have no problem with the focus of either post WW2 Russian lenses, or Leica lenses.