If I remember right .. On the 700 and 900 even the 600 and 800 Iron Bias is only available when the operating frequency is set to Multi. But I also am new to using the Iron Bias function on the 700 also..
Watch this one: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Z8d02pmAgp0.html Also, you will never eliminate bottle caps unless you notch out a huge portion of the VDI range. Hence missing other vaulable targets. This video helps you identify them, then you decide if you want to dig them. Although each to their own, I highly suggest digging everything when you first start out to learn the tones of every kind of metal targets. I dont usually dig iron as an overall percentage but recently I've found lots of junk jewelry digging iron tones which is always cool in my opinion. In the end, dont worry, bottle caps still fool me sometimes after thousands of hours swinging a equinox. Just put in the hours/miles/etc, and you will find something good! Always feel free to ask questions and I will do my best to help out!