I came across this site for making percussion caps out of pieces of soda can and toy caps:
http://www.beartoothbullets.com/open...en_sight.htm/9
This seems encouraging - I'd think it would be a lot harder to make percussion caps than tape primer.
I've come across some original maynard primers for measurements and specs, and I've ordered some toy caps. I'll let you know how I make out.