Old Caps do work
Mykeal; I found some caps in my garage last year, that I had forgotten about in one of a thousand junk boxes stacked out there. I had used some of these caps way back when I had bought them. This particular cap container wound up in a junk box, probably from my wife doing house or car cleaning thing. These were Eley musket caps that were purchased from a friend in 1985, who had a small embrionic gunshop business then. I have bought thousands of caps since then. Anyway, I put these old caps in my shooting box after I found them. When I went shooting, the old caps behaved just the same as my new caps. You could not really tell any difference, visually or ignition-wise. They shot the same.
I had them stored in the factory container, which is pretty much air tight. That must have had a lot to do with it.