New rifle w/less than a hundred rounds...everything seems as it should be with one exception -- chambering a round and subsequently ejecting it without firing shows a dimple (that looks just like a FTF: light strike) on the primer.

I had inserted a mag, pulled the charging handle and released fully to let it chamber the round as I prepared to shoot.  I was interrupted so I then proceeded to clear the weapon by releasing the magazine and pulling the charging handle to clear the chamber.  The ejected round shows what looks like a light primer strike even though the rifle never left the safe position and I never pulled the trigger.

I always function test after cleaning and I've since disassembled the BCG and everything seems exactly as it should be.  I don't think I've ever paid attention to a round I've ejected like this in the past and I haven't had an opportunity to experiment further.  Thoughts?

Normal.

Firing pin floats

Quoted: Normal.

+1 Yep, no firing pin spring to hold it back. I have never heard of a slam fire from this though.

Perfectly normal.  The AR (and many other military rifle designs) utilize free floating firing pins.  The inertia of the BCG traveling forward causes the firing pin to lightly strike the primer; that's why military ammunition uses thicker primers.

Good to know.    As I say, I don't think I've ever examined an unfired but ejected round from an AR before.  Thanks for putting my mind at ease -- and quickly too!

Normal situation for a floating firing pin.  Never charge a military semiauto anywhere else but with the barrel pointing down range.  Commercial ammo has a better chance of going off in this situation as the primers are softer than military ammo.  Slam fires, as this is called, are rare but they do happen.

My F A Ls have firing pin springs and they still dimple the primers.

Quoted: Normal situation for a floating firing pin.  Never charge a military semiauto anywhere else but with the barrel pointing down range.  Commercial ammo has a better chance of going off in this situation as the primers are softer than military ammo.  Slam fires, as this is called, are rare but they do happen.

+1