I noticed that on the primer of each round that is chambered in mr AR,a light firing pin  indention is created...

I never noticed this before, and I'm wondering if it is cause for concern..

I'd hate to chamber a round and have the firing pin hit hard enough to fire a round off..

What do you all think?

Completely normal.  Don't worry about it.

That's normal for any weapon that has a floating firing pin, like the AR15. You also see that with M1 Garands, M1A1s, etc.

As long as you use good ammo you won't have a problem. Reloads with primers not seated might be a problem.

Edited to add: Due to the floating firing pin design, you should never drop a round in the chamber and let the bolt fly. Let the bolt pick up the top round from the magazine.

As folks have said, normal for a non-spring-loaded inertia firing pin. A few things to minimize a slamfire:

1) Use mil-spec ammo - it has harder primers. CCI is also famous for using harder primers.

2) Don't constantly rechamber the same round.

3) Spec firing pin length. Guages are available from Bushmaster or Brownells.

4) Consider a QMI Titanium firing pin. Less weight = less inertia. I don't buy into the faster lock time hype, but it is lighter.

Finally, as said, always watch the muzzle when chambering.

its normal