All of the Russian lenses were made to the Zeiss Contax standard. But there were deviations in actual focal length, and it was common to have individual lenses adjusted by a repair shop for each body. Many of these lenses are 30~60 years old, and could possibly have gone through adjustments.
But: A Russian lens built to the 52.4mm Zeiss standard, within spec, will benefit from being shimmed for the Leica 51.6mm standard. You have to pick the point of best focus, because it is going to deviate. A Leica "50mm lens" will travel 0.1mm less than a Russian "50mm lens" as you move it from 3ft to infinity. That is what the RF pickup of the Leica expects, and when you put the Russian lens on it- it does not change its motion. So to use the Russian lens close-up and wide-open, you have to move it out 0.1mm. That means you give up infinity focus. Stop down to F4, Sonnar focus shift (and Tessar focus shift) makes up about half the error.
SO: long story short,
J-3, J-8: benefit from shimming.
I50, I61, I22, I10: if you pixel peep, benefit from shimming.
J-12, usually you are Okay. If you pixel-peep, benefit from shimming.
J-9. You can only make it focus correctly over a few foot range when used wide-open. You can move the rear module in, later black lenses have a secondary shim. Then shim the main module. I gave up on the J-9 for use on a Leica and use the Nikkor 85/2 instead. The J-9 will go on the EP2.
J-11, stopped down- maybe, I have not tried on a Leica. I use mine on a Contax II.