Not too far off topic- but of interesting note... the Gun Smith I apprenticed under told me that some of the wartime Mauser building countries used iodine on bbl threads to lock (rust) together the bbls and receivers. I could see that happening with the need for something cheap, quick, and low cost. And, I'm sure that some of those factories didn't always have the luxury of taking the time to cut threads to the standards they would have in peace time. And, it esplains why I've seen some pretty dirty/rusted barrel shanks once they've been pulled.