It depends on the year of production and the maker for the reproductions. I believe that the very early repros were exact copies of the originals. Within a short time, changes were made in order to distinguish forgeries. I do have a barrel for a repro Colt plus and original Colt navy and there are differences in the size of the cylinder pin and dimensions of the barrels. At the same time I also suspect that some parts like springs and hands and perhaps the hammer may be very close to the originals and probably interchangeable
cheers mooncoon