I attempted to refinish a nickel plated 1st model M&P 32-20. I had no idea how much damage can exist under an originally nickel plated firearm. It is truly amazing, I would never again attempt to refinish any nickel finish that wasn't just worn, if there were any deep pits scarred with rust I would leave it be and do everything I could to stop the existing rustification including the possibility of deep bathing in anything that kills rust, then scrupulously cleaning and a final cover of wax. My effort left me with a parts gun that functions, if the rust had not been a serious I could have finished it in something that provides enough of a surface cover to fill some of the damage. Good lesson as it wasn't much of a value going in.