Looks like hollow brass to me or is that just an optical illusion? A bit too thick a wall for a shell casing, isn't it? Maybe a gas line orifice, nozzle or fitting?
Only a guess,if it is a powder measure it would hold between fifty and sixty grains. Holly wood showing powder poured from a horn or flask is a big no no.
Also a particular charge/load will be best for each individual weapon and between different calibers of course.By cutting a charger /measure to length corresponding with that loads volume it can then be attached to shooting bag. For a smooth bore using shot an equal amount of powder and shot utilizes same measure. Pic shows a shooting bag to accompany a flintlock with pan brush(horse hair probably) for cleaning pan and pick for touchhole along with measure for powder. Were your item a large ramrod tip for smoothbore it would likely have a hole for pin through it through wood and possibly a dished face.