So I finally had a chance to break in my new RRA midlength rifle, also did somewhat torture testing to see how it functioned under heavy rapid fire....It functioned perfectly without any malfunctions, however after 6-7 30rd mags the barrel/ handguards were extremely hot- water sizzled on the barrel!

The question is what is everyone else's experience, is this normal; what about LE and Military out there, how do our guys handle barrels heating up in fire fights when they go through their 5-10 30rd mags burst/ full auto??

Normal. I usually let my barrel cool down after rapid firing one mag but you could shoot more b4 heating up the barrel to the point you described. you probably didnt cause any damage if you have already broken the barrel in properly.
-jls7

Thin barrels may cook off after 155 rounds of auto fire.  5.2- 30 rd mags. This means that the gunpowder may ignite from the heat of the chamber and could fire unexpectedly. I think Hbars can go longer but also take longer to cool.

Quoted: So I finally had a chance to break in my new RRA midlength rifle, also did somewhat torture testing to see how it functioned under heavy rapid fire....It functioned perfectly without any malfunctions, however after 6-7 30rd mags the barrel/ handguards were extremely hot- water sizzled on the barrel! The question is what is everyone else's experience, is this normal; what about LE and Military out there, how do our guys handle barrels heating up in fire fights when they go through their 5-10 30rd mags burst/ full auto??

We dont dump mags that fast.  The m16 platform was designed for sustained fire of 15 rounds/min.  The usual carry was 8 mags when rigged normally, 10 if paranoid.  If you are sprayin like that, then too much ammo is being wasted for sustained operations, and expect to get a thump on the helmet on your next break.