Do you really feel that fast reloads were typical use? There has been some discussion concerning the fact that it may have been common for J Q Frontiersman to shoot then clean his rifle before reloading. Considering that they may have not done a lot of shooting that is likely common. While loading in a hurry may have been done on occasion, it was likely done with more an attempt to get something shooting than any attempt at accuracy. When running buffalo off horseback the Metis were said to have put ball in their mouth and loaded directly from the horn. Try to use a powder measure off of horseback. You woauld not put it in your hand either. Burst barrels were also not uncommon. There were also references to plains rifles having barrel blow. There were also references to double charging rifles, which implied the use of measures. Cooper used to reference light loads in rifles in his Leatherstocking tales. From most references I have read, we tend to use heavier charges today.
DP