Burrard mentioned these cartridges were normally loaded with large shot for waterfowl & contained bonedust. In the 1913 Lefever catalog a section titled "Buckshot Loading" it is recommended to first see the shot chambers a little loose in the muzzle, then to put in a layer of shot, fill cavities with light, fine substance, like bonedust or fine sawdust & repeat until three layers are placed in shell.
Very little new is there??

Miller/TN
I Didn't Say Everything I Said, Yogi Berra