Compression is a fact of life in reloading with black. I don't reload for an original Spencer, but do for one of the replicas in 56-50. In Starline brass I can load as much as 40 grains, but it is compressed with a Montana Precision compression die, after a wad is placed over the powder before I seat the bullet. I adjust the compression die so the bullet is in contact with the wad and does no compression when seated. This is the same basic method I use for loading 40-65 and 50-70 with black. Original loads used some compression. The amount of compression can vary based upon powder brand and granulation.