Get a piece of hard copper pipe about 6" longer than your bore and
a hardwood dowel to use both for forming the foil bag and pushing
it into the chamber. Form the foil around the end of the dowel, pour
powder into foil cylinder, close open end, place bag in tube, place tube
in bore against chamber, push bag through tube into chamber with
dowel and then pull the pipe back out.
This setup can be adapted for any size of powder chamber.