O.K.  I'm new to AR-15s.  While considering which gun I want to buy I've been looking at the RRA A4 Std., which comes with the Wylde Chamber.  I wanted a gun that would absolutely shoot 5.56 NATO ammo.  Is there any type of problem with 5.56 NATO ammo associated with the Wylde Chamber?

If no, then why doesn't every manuf. use the Wylde Chamber?

Because a chamber that is more generous has more room for crud and out of spec ammo. Plus a NATO chamber is "milspec" and we all know how big a deal that is to some users.

Quoted: Plus a NATO chamber is "milspec" and we all know how big a deal that is to some users.

Well, this I don't know about. ALL I wanted to be sure of is whether it would cause any type of problem.  But thanks.

A Wylde chamber will shoot 5.56 with better accuracy than a Nato 5.56 chamber. It will also shoot .223 ammo.

Quoted: A Wylde chamber will shoot 5.56 with better accuracy than a Nato 5.56 chamber. It will also shoot .223 ammo.

Thank you very much.  The pressure levels were my main concern.

Quoted: O.K.  I'm new to AR-15s.  While considering which gun I want to buy I've been looking at the RRA A4 Std., which comes with the Wylde Chamber.  I wanted a gun that would absolutely shoot 5.56 NATO ammo.  Is there any type of problem with 5.56 NATO ammo associated with the Wylde Chamber? If no, then why doesn't every manuf. use the Wylde Chamber?

You shouldn't have any problems with a Wylde Chamber when shooting surplus ammo.

Why doesn't every manuf. use the Wylde chamber?  The Wylde chamber was designed for NRA highpower rifle competiion, specifically a chamber that could accomodate well the heavy bullets used for the slow fire prone stages of that sport.  IMHO, RRA's choice to use the Wylde Chamber is the weird one, especially in a non-match rifle like its A4.  

The chamber issue has been overthought on this board, IMHO.   Unless you're a high-master level highpower rifle shooter, or a very good scope-varmiter, you're not gonna notice the accuracy difference bewteen any of the three chambers.   Colt and Bushmaster (among others) make very good 5.56 chambered barrels.   If you really want to shoot primarily military ammo, I'd go with the 5.56 chamber - but if the RRA really is what you want, get the RRA and don't sweat it.