Look how it looks like it annealed the brass only at the mouth. Weird! I would have though the heat would have been drawn toward the thick end of the case. It only affected the brass out where it is thin. The head looks as normal as can be on these. I took one in and resized it without lube and it resized nice, like new brass. I bought this old Winchester brass in the 1980s and I've been drying my brass this way for probably over 20 years I can't remember ever seeing a split case on any of these. I wonder if this is why. Probably just my imagination. This is what I pulled out this morning. Guess it's time to buy a 20 amp timer with multible outlets so I can plug in my tumblers also. By the way I clear the bench off around the heater when I'm running it. I doubt it ruined the brass, just annealed it some. Some of my 9mm brass turn colors a little at the mouth every time I dry them. As long as the case head didn't change color. Pretty shades of blue out at the mouth.