Fire with 209 primer onboard. That short plunger pin will eventually loosen and extend beyond it's normal stop-point. I believe it is ever-so-slightly tapered wider on the hammer end. You may create a groove point in it by firing the Omega without a 209 primer.

I don't know the correct/technical names for alot of parts on the Omega. I'm too lazy to dig out my illustrated page of my manual for a better explanation. Two NFL playoff games on TV are a bigger priority today. I'm watching the last game as I type this reply. Hope this helps!