.25-20 brass is the most difficult to obtain. I have resized both .32-20 and .218 Bee with good results. Even tried the 7.62x38 Nagant brass, not so much. Plus the rim difference is about .012 in thickness from .25-20 to 7.62 that is a problem. I have seen and tried the tiny Oring trick, also not so good on the results. After pushing the Nagant thru a forming die much of it will fold inward and form a crease, end of that brass. I have had some "success"; however, I do not care for the process and do not recommend it. Push the brass thru the .25 resize die, slowly. Trim the very long neck down, resize again and it is close, however there is a ring near the cartridge base just head of the rim. The ring is very small, perhaps .001 in height but enough to prevent chambering. Using a jeweler's file and lightly touching the ring I can get it in the chamber, but filing on a cartridge in that area is not a good idea.
As to the nickel .32-20 I will pick up a box of 50 and see what happens. Depending on case mortality rate I will determine if it is a good or bad idea.