I always used to use fired brass for a snap cap. But I figured I'd get some real ones for my CPO Sig. So I bought a package of six Traditions brand (the Fiddler on the Roofs in me likes that) at Parro's nice new store in Waterbury for a pistol that allegedly doesn't need them and had at it. I think it's good for the manual of arms part of learning a new gun. Now there is a nice crater in the brass "primer" and the extractor is beating up the base of the cap. My question is: When has the snap cap had the radish and needs to be replaced?
I use mine quite a bit, can't remember the brand but a deep dark red all metal. the primers on mine are sprung, so they wear longer, some dummy rds are not meant to used as snap caps.
My traditions snap caps are beat a bit too. I imagine as long as they cycle thru and the primer springs back they should be o.k.
You can lightly sand off burrs if they are hanging up, but do it lightly.
I don't see any reason to replace them as long as they're still intact. I think you'll blast the plastic tip off the nose of the round (from the internal spring putting its pressure on that spot) before any other part of it wears out.
The ones Colin mentioned are probably A-Zoom.