Where are you trying to seal the wires? I use a terminal block and epoxy the hole and wires that run from the bay to the terminal block to keep the av-bay sealed. If you are talking about sealing them in a "BP cannon" I'm not sure what you mean. I use a small cup on the face of the av-bay and just put some dog barf over the match head and powder and masking tape to hold it in. If I want the charge away from the av-bay, I crease a piece of duct tape, lay the match in, pour the powder over it and close the tape around it. If you're using smokeless powder or BP substitutes, that's a whole different problem I have no experience with, can't help there
.