Buy a mom trigger grind off the surface without getting it hot and then try to drill it. If you know anyone with a hardness tester have them check it. A thin layer of hard metal will not give a true reading because the soft metal under it will give more than a piece that is hard though out. I am betting a mim part is completely hard. If I think about it I will check aim vs cash hard part next time I have a minute in the shop. Been busy getting camp trailer updated for the summer