User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-187.149.97.198-20121010003827/@comment-28303251-20121012205145

"In Monster Hunter Portable 3rd, any form of explosive damage (from Barrel Bombs to Gunlance shells/Wyvern's Fire) will heat up Agnaktor's hardened parts, making them soft again."

From Agnaktor's page, explosions only.