I have been duplexing BP with 5744 (or equivalent smokeless) for more than 20 years but not really with any rational. I have always used 5gr of smokeless as my kicker and then an amount of BP to come up with a "100%" charge. As an example I would load 5gr of an unnamed smokeless and then determine what percentage of a full charge of that smokeless the 5gr was. I would then load a BP charge decreased by that same percentage. This produced some very clean burns in 45-70, 45-90, and 50-70. I noticed in 45-110 and 50-90 the barrel was not so clean. I have been thinking I should use a larger smokeless charge in these calibers. Perhaps there should be a constant ratio, maybe 10-90%.

One other curiosity; since the Sharps 50-90 and 50-100 used the same case should the ratio of smokeless to BP remain the same if loading 90 or 100gr BP?