I hesitate to post this but......... a friend and I were shooting clays at a prodigious rate. He was shooting a 28 ga Ruger Red Lable bottom barrel only. The 28 gauge has separated barrels secured at the breach and muzzle only. I happened to notice after a lengthy session the barrel appeared to have an arc downward. I had to apply a straight edge to it to confirm and yes it had deformed presumably from the heat. I've never witnessed anything like that since.

Dodging lions and wasting time.....