I think you need a chamber cast. The rifle left the factory chambered in 25-25 Stevens. Somewhere along the line, either to rescue a shot out barrel or to be able to shoot a old gun that was chambered in a long obsolete caliber, someone reworked it to 38 Special. Since the 38 Special was developed and first saw use in 1902, it may have even been done when the rifle was new, but I doubt it.