I have noticed that the live rounds that have been cycled all have a slight indentation from the firing pin.  I was curious if this is a problem or it just occures and I shouldnt worry?  Its a bushmaster XM15 E2S A3

I understand this is a "normal" result of chambering a round since the AR15/M16 firing pin is a free-floater.

Another reason not to chamber a round unless the barrel is pointed in a safe direction and you are preparing to fire.

This is also normal for the M-1 and M-14 Rifles. It is as JoeInCt so perfectly states, "Don't chamber a round unless the barrel is pointed in a safe direction." Also, it is a good reason not to use "soft" primers for a weapon with a floating firing pin. Just remembered another.A 1911 Colt Auto (or clones) with a round in the chamber, if dropped muzzle down on a hard surface, will fire.

Milspec 5.56 ammo, and handloads that use Remington #7 1/2 primers are perfecly safe. The slight dimple that chambering a round won't do anything nasty.

Given the popularity of the AR15, it may be that all the ammo manufacturers are now using primers that are safe in the AR, but I recall that when the AR15 first hit the civilian market there were some ADs with soft point commercial ammo, and especially handloads that used the standard small rifle primers. That's why Remington brought out the 7 1/2 primer, and gave it a slightly different color, in the first place.

Other than that, don't give the tick in the primer a second thought[:D]

Like everyone has said, don't worry about it.

From http://ammo-oracle.com/:

"A gas-operated semiautomatic operates on gas bled from the barrel.  This gas is channeled to the bolt operator, which blows the bolt open and ejects the spent shell casing.  A heavy spring then returns to bolt carrier to the closed and locked position on the next round.  In the case of weapons with free floated firing pins (SKS, AR-15, etc.), the inertia of the firing pin carries it forward and it strikes the primer as the bolt closes.  (The "slam").  Generally this will dimple the primer and leave a small indent.  This isn't anything to worry about as primers for centerfire .223 and 5.56mm are pretty "hard" and aren't likely to be set off by this impact."

There is a great picture of this if you read ammo-oracle, which you should do anyway.  It will answer most (? all) of the common 5.56 ammo questions.