Alarming Observation?

Perfectly normal. The free floating firing pin on a carbine always hits the primer when the bolt closes. I doesn't hit hard enough to actuate the primer. They all do it. Nothing to worry about.

Nope! Extremely unlikely that it would go full auto on you. That would only happen if the firing pin somehow got jammed in the forward position. As long as the firing pin is loose, it doesn't have enough momentum to strike the primer hard enough to fire.

I need to mention that slam-fires are real and when one personally experiences a slam-fire, it’s a revelation. I had one in a Remington 742 30-06 and happened to have the rifle pointed down-range. You will become anal about cleaning and inspecting bolt internals and firing pins as well as sticking to the hardest primers the action will fire if reloading. Creates a mind-set that the weapon might fire anytime the bolt is dropped on a live round….and it might.

Factory ammo. I recovered the brass and it had a very light strike. Think is was a very soft (defective) primer.

RE: Sellier & Bellot 30 cal rounds.  It is evident S&B crimps the primer during insertion into pocket.  I learned this when reaming the S&B primer pockets; if I didn't ease the reamer into the pocket VERY,VERY slowly the reamer cutters would grab into the brass.  Many cuss words later I finally freed the reamer teeth from the brass.  After reaming the pockets to SAAMI specs. and comparing primer loaded brass of reamed and non-reamed S&B brass it is obvious the S&B pockets are shallower than SAAMI.