I read an article on it, can't remember who wrote it, about using 3031 as a booster for black. Really shot well in the long cases, and the short .50/70 as well. I was getting 3" for 5 shots at 100 meters with the .50/70 original barrel and a shortened Lyman #515141 bullet. I was using jacketed and RCBS 500gr.(545gr.)cast with duplex loads in the 3 1/4", .45 Rolling Block.