At test depth the bottle cap was detectable until i reached a level of 4 5 when it finally faded away.
Garrett at gold depth test.
The bobby pin at depth was lost at around 2 or even less.
The sniper coil is hot in trashy areas and gets great depth for a small coil and is sensitive to small objects.
It also has the best look and feel when it comes to ergonomics.
The ace 250 is superior when it comes to locating coins relics and gold both in the sand and in the water.
Given those results were i to adjust the discrete mode high enough to eliminate the bottle caps i would lose the smaller rings and just barely hit on the larger targets my army.
The 12 inch coil will get you another 2 3 inches in depth and operates and pinpoints just like the standard coil.