One liter bottle screw caps around here come in at CO 38-41 and even higher for the larger caps. I'm curious if anyone has experimented with adjusting the variability and/or limits to help audibly discern them? If so, what's the number(s) you've chosen that helps you differentiate a coin from a screw cap or other junk targets?

One trick that works is to lift the coil ~6 and if it still sounds off then you know its a screw cap. Problem is this trick can really slow you down in an area with lots of screw caps. So I'm hoping there's a way to discern them strictly through audio.

Thanks
-Alex