I've read about the higher pressures that can result from 5.56 ammo being used in .223 chambers. Has anyone actually experienced issues directly attributed to this? If so, what issues did you experience?

Yup, I've read up on it. I was just wondering if anyone here has personally experienced those issues. I guess you could restate the question as: What are the odds of issues developing as a result of 5.56 ammo being run through a .223 chamber?

Most of the .223 chamber ARs are not to the same exact .223 spec. as the bolt guns.  If I were you, I would contact the builder of the weapon and ask them.  

Example....
Oly PCR1-3s are .223 chambers but marked with 5.56 on the barrel.  So...which is it?  Oly claims you can shoot both.  I have shot thousands of rounds of 5.56 M193 ammo in my .223 Oly without a problem.  No feed problems, no extractions problems, and if it were going to KB, it would have happended 10,000 rounds ago! [;)]

If the company that builds your AR claims you can shoot 5.56, I would shoot it without the first concern.  

Check the spent cases for signs of excessive pressure around the primer pockets. The .223 chamber is a little tighter than the 5.56 one, but not tight enough to cause problems with good factory ammo. I've fired XM193, Q3131A, S&B SS109, SA 5.56, and Hirt in my match chambered CLE target upper with absoulty no pressure problems. If your rifle dosen't have any problems with 5.56, then don't worry about it.