Goody,
At one point in time, R&D produced four drop in cylinders for the Remington revolvers.
This was because there were slight differences in the arms made by ASM, Euroarms/ASP, Pietta and Uberti in regards to the ratchet at the rear of the cylinder and the bolt stop location on the cylinder.
Some of these manufactures cylinders were pretty close, but, It may require internal fitting to get the new conversion cylinders to work. (if the wrong cylinder was ordered for that revolver)
If one did this sort of fitting for the cartridge cylinder... then the timing would not work well for dropping in the percussion cylinder.
Another words, you no longer had a convertible Cartridge to Percussion or Percussion to Cartridge revolver.
I hope this helps answer your question?
My best,
Blair