I have been making progress on the learning curve of care and feeding of black powder single shot rifles-no more "white powder". I found 2.4, 2.6 and 2 7/8 Sharps' lumped together under .45-100 in my edition of "Cartridges of the World". The comment was made that these cartridges of varying length carried similar powder charges. Length , this source continued, was to accommodate the same charge in heavier cases made for repeated re-loadings and different bullet weights. Is this explanation correct? Thanks for the help.