Hi Diane. We have this problem all over Scotland. If there is a massive amount of iron, and the peices are large, I would run at -16 iron mask. Even at -10 to zero iron mask, large iron will give you false signals (ie cant make up its mind). At -16 you will know when your over iron. As jim has said listen for any high tones ,run at max vari and limits (threshold at 1) so you can hear good targets. SLOW right down and listen for any high pitches, DONT watch the screen. Also I would try and keep my sens down as high levels will attract the iron.Try a low auto sens..
Ive been detecting for over 15 years, Ive had the XS for over 6 months and I am only just starting to understand it. When you do youll love it.
Hope this helps.