Hello,
I use the 705 with DD coil (have both the 6" and 10.5") to nugget hunt in the mountains north of Los Angeles, CA. Mineralization in the San Gabriel Mountains where I work varies from low to very high, but in general, I find much of the area to be moderate. You will encounter high, tertiary riverbeds (not all of them, but the richest) will be so iron-rich, that the machine will blank on the entire cliff (with iron mask on), or not shut-up with it off (or in All Metal). Many, many detectorists have found nuggets in the area, but you need extreme luck (or tons of time to dig thousands of targets-most of which are trash). There's over 150 yrs of human trash EVERYWHERE, and I am constantly digging pull tabs, clad, casings, tiny bits of wire, aluminum, square nails, lead shot from places you would think humans have never been. Forget areas near the modern campgrounds or roads. However, all is not lost, you need to be patient, and continue the hunt. Working bedrock is the best method, but I literally pulled a dozen trash targets in about 5-10 minutes. I was told that 13 detectorists had already worked the same area earlier in the day. Yet, none of them found the 1.7g nugget on the surface-a sluicer told me about his find, chuckling about the detectorists who went right over the spot.
Other methods: climb way up high to the benches, and work them. There's one bench I work (it towers over 100 ft vertical once you reach it), has NO trash, but also no signals. You can spend hours and get nothing other than changes in ground mineralization. Very, very boring-but a signal is likely to be gold. Guess that's why in the 1870s, that bench was hyraulic mined by a 5 man crew, whom took 3-5 oz/day. If you highbank 5 gallon buckets, you'll get nada. But not all of the benches are the same...some have gold, and others do not...crazy, but true.
Plenty of old cabins, forgotten mines, and campsites from the 1800s....2 tribes lived in one canyon for at least 8000 yrs, and in the late 1700s, the Spanish, then Mexicans came. It's very easy to find all the 19th century mining trash you like at tons of sites.