I know this might seem like a stupid question, but here goes.  I am buying my first AR on Tuesday from  a friend.  I know it is a colt, and I believe it is a CAR.  My question:  Can I safely shoot 5.56 mm ammo, like the XM193 and XM855.  hinking.gif I thought that .223 and 5.56 mm were they same until I saw this:  

Fulton Armory

Assuming that I can shoot 5.56mm,  any opinions on weather the XM193 or XM855 is the more effective anti-personel round.  I realize that the lethality of the 5.56 bullet is due to fragmentation only above 2500 fps (i think) and that the XM855 is slower because of increased mass.  However, how much consideration should be given to intentionl penitration of barriers, (bad guy behind a wall or wearing body aromor) which favoirs a steel tipped round.  

Reguarding accuracy, how realistic is it to switch between the 2 rounds without losing accuracy nor resighting in the gun.  ?

I will be using a shot barrel I believe it is 16 inches.  I don't really care about the difference in price.

All Colt CARs are chambered in 5.56 (you go by what is marked on the barrel not the receiver).

Is 5.56 ammo in a Colt CAR dangerous?

In the hands of the right person, it's DEADLY

+1 with what Forest said.

-------------------------------------------------------------------------------- Is 5.56 ammo in a Colt CAR dangerous? --------------------------------------------------------------------------------

I only shoot .22 LR and .38 through mine

Yes it is! But dont stand on that end of the weapon and you will be safe.

+1

Never point gun at anything you don't want to injure, kill or cause great bodily harm