I had my first dud a couple weeks ago. Just like yours - solid hit, no nothing. Three tries, nothing.

Intended to break it down, but before I did thought Hey, I'll try it in another gun. Boom, first time!

Had just started using some CCI primers (couldn't get my usual Winchester). I guess they really are harder. Gun that failed was a 60-7 with a bobbed hammer, so likely a light hit. I replaced the hammer spring and loaded a new box with CCI primers to test it out next time I go.