Not sure what the expected barrel life was, but I've seen M-60 machine guns go through 2,000 rounds in about 15 minutes. The barrel wasn't glowing, but was DEFINITELY too hot to touch. Once cooled down, you couldn't tell the bore from a new barrel. Not sure what the total round count was through that barrel, but 1,500 to 2,500 rounds per firefight is normal, and a typical barrel went through several firefights.
I've also seen them so hot they glowed and even though the trigger was released, the rounds would "cook off" after a short delay. At that point, the accuracy was pretty well shot.