Hi Rick,
I use mine mostly for jewelry hunting but my setup is basically the same the relic hunters use. Iron disc as low as you can tolerate.. depends on the amount and size of the iron. I never go above 8 on the iron disc and try to keep it around 6. The only iron I have problems with is stuff like RR spikes large nuts and bolts, iron rings ect.. Thick heavy stuff like that. Mostly logging and farming related iron up here and the 1270 likes some of it. Yhe usual tricks works well to ID most of it, of course you would probably want to dig the cannon balls and frags down there. LOL
Once you get some time on it and learn the audio the 1270 will pull non ferrous stuff out of iron real well for you.
Tom