Interesting. I never thought of the blanks from the hardware store. Was fixated on 209 primers, thinking them abundant and inexpensive. If memory serves, which is debatable, those things come in different strengths. Is it likely to matter which I need to reach a charge through a 4.5" vent length?
Had thought of quills, but I prefer a percussion ignition, and have had spotty luck with friction primers lately.
Thanks again for the help. Learning a lot already!