TR, 1200 rounds in 5 days comes to 240 a day
Average day at TR is about 8 hours or 480 minutes.
Total averaged firing rate is one round every two minutes. At that rate, you could hold the barrel bare handed.
TUMOR, if you are in a SHTF situation, whether your barrel gets hot or not is going to be the least of your concerns.
I have noticed that if I start with a cold barrel and run the first 30 rounds through in 30-40 seconds, the barrel gets to be hot, but I could hold it with a leather glove and no hand guard. If I blast through 100 rounds or so at that speed, then the handguards become necessary. After 200 or so, I don't want a bare hand anywhere over the top of the hand guard as the heat risint up an out gets very uncomfortable.
I don't know of any home defense situations where a person has blasted through and entire mag, reloaded, and kept fighting. Cops and bad guys fighting the cops may do this once in a while, but generally speaking, if you get to the point where you need a mag change, the fight is already over.
By the way, don't confuse shooting in semi-auto as being somehow limiting to heating up your gun. Granted, it isn't as fast as full auto, but a buddy of mine (and I am sure many people can do this) can empty a 30 round mag in 8-10 seconds while firing semi-auto. At that rate, the barrel heats up quick.
308wood is right. If you took the carbine course at TR and don't know if you need heavier duty handguards or not, then something isn't right. Either you missed some key points of instruction or you have not spent any significant amount of range time outside of TR practicing what you learned. From the sounds of it, you may or may not need fat handguards, but what you DO need is to spend a lot more time firing your shorty so that you can make an informed decision on what safety-related parts you wish to keep or change.