I have a 4b and a gm 3 both with concentric coils. Never found anything with them. i moved to gold country. I want to start going out more. id like to get another coil, would you recommend a 5x10dd or the little dd shooter?
I also prefer the 4x6DD - there tends to be less trash under it (its smaller), its also more sensitive to small surface layer gold than the 6X10DD. I tend to look in rocky areas - the small size fits better.