First, slug your barrel. The bore diameters for 38-55 can vary considerably. An excellent outfit for all paraphernalia relating to BP cartridges guns and reloading is Buffalo Arms - whether you use black or smokeless powder. Really nice people and very knowledgeable. (www.buffaloarms.com
If your bore diameter is near 0.380 inch, you may have trouble chambering a cartridge with the proper diameter bullet loaded in Winchester brass - it is thicker walled than original 38-55 brass (It is, in fact, basically their .375 Win brass). Starline makes 38-55 brass of the proper wall thickness and that should work just fine - and it is less expensive.