The 44 magnum blanks that I describe in my article “Reenacting with a Spencer” for use in a 44 Russian reproduction Spencer seam to also work in the reproduction Spencer in 45 Schofield.
I was at a reenactment this weekend and had my blanks with me. I provided some to a fellow reenactor in another unit that has the 45 Spencer and he tried them in the afternoon battle. He said that he only had on problem and this was when one would not feed. It cleared quickly and he continued to fire.
I put this here just in case anyone has a 45 and wants to shoot blanks out of it. The article can be found at:
http://www.9thnycavalry.webeditor.com/spencer_article.html