Man
The best I can tell you from what little experience I have with my Tejon in certain "Hot" soil areas & there are Quite a few in my area.
Places where a good fist size or larger rock will make the machine sound off.
What I do on these sites W/Tejon..First Have A-LOT of Patience , then ill turn the Sensitivity down to around 7 ' maybe as low as 5. Run the Bottom right Disc between Foil & Nickel (depending on the Noise). & the top right disc on "Tab" or above (For those for sure targets). Of course Ground Balance as best u can, then reset it every now & then.
The main thing I noticed in Hot Ground with the Tejon is 'On a Hot rock /false Target' the machine will not Pin-point.
On a good target it usually pin-points pretty well on 22 shells / bullets ,Shot gun brass etc.
Of course all ground is Different ,So lot's of Patience or Dig most Everything.
Good Luck On your Hunt.
Davers