It does look like it's been subject to extreme heat.Tried my hand at some barrel heat weathering, and I’m pretty happy with how it looks.
I painted shaded highlighted the gun. Then with an airbrush, I lightly sprayed a very watered down army painter weapon bronze round the end of the barrels then a very watered down Vallejo imperial blue(blue/purple) followed by a watery Kantor blue then some matt black at the end. Make sure you leave a little of each colour showing.The heat stress looks excellent, could you describe the process you used