Cause of miss fires found

[superx10]

I recently have had a few miss fires with new Palma brass and CCI 450 primers and on taking the offending cases home and pushing the primers home hard with a foster press they then ignited.

[Tim L]

Yep I think that issue is cause for more misfires than it's given credit.
I've recently noticed with both BR4s an S&Bs that the spider is proud of the primer cup. I can't say for sure if that means the spider isn't secure so i just make sure the primer is fully home in the primer pocket so it doesn't matter.

[bolster55]

Hello All
The anvil(what you call the spider), has to sit proud of the cup to stop premature ignition. When seating a primer it requires "feel" to know when the anvil is seated inside the cup and is contacting the medium at the bottom of the primer cup. I use a single "shot" primer seater, this gives you feel when seating the primer.
There been many articles written regarding primers, one German Salazar has an excellent article, plus Manly others.