I have!
So far, so good on mine with about three full mags through it.
I wouldn't recommend multiple Beta mag dumps, however, as it will get that barrel awfully hot if you use it as a sustained fire platform.  The 9mm has a lot of things going for it in semi and full auto, but I personally wouldn't want to run more than one Beta mag through it without a little cool down time between mags.  I've got my personal toys hot, without long-term problems, but it can, as with all ARs, get pretty hot, pretty quickly.
Steve/RRA

It shouldn't be a problem.  Just bear in mind that it is a rifle, not a general purpose machine gun (GPMG) built for sustained auto fire.
All ARs, regardless of caliber, heat up with use.  The faster you fire it, the hotter it gets.  The longer you maintain that rate of fire, the longer it stays hot.  Even the time spent changing a magazine helps the rifle dissipate heat.  I wasn't so much concerned about damaging my barrel by firing long strings on occasion, but everyone I know who gets a Beta mag inevitably tries to see how fast they can dump it...or worse, them.  Sitting down with 20 loaded thirty-round mags and firing them one after another after another wouldn't be ideal either.  In reflection, I could have worded my initial response a bit better, and will edit it appropriately.
Steve/RRA