So I just finished my first AR build, and of course I needed a free float handguard. Its all good right? Well, first time out to the range the other day I noticed the handguard getting hot. Its just a standard aluminum freefloat, no rails. But after only 30-40 rounds, it was unpleasantly warm, and after about 20 more rounds, I had to let it cool due to it being too hot to hold. Is this normal?