Hi Dan, Thanks for the post...
First I have to say I'm no expert when it comes to dealing with these as I hunt mostly Colonial sites where round artifacts are welcomed. But, I can understand where they could be a bug-a-boo in a park setting for example. First I would reccomend finding John's "Coinstrike Homepage" for several tips including caps. Here's a portion:
>>>>Regarding digging up bottle caps and tin can lids with the Coinstrike. The simple answer is you can back off the settings on most any detector and notch out the bottle caps. On the CS you might be able to in some cases. Reduce the Sensitivity and Threshold to test. The majority of the time nothing will keep a crown type bottle cap from reading as a "coin" signal. The CS likes round things including harness rings. And as Chuck VT says bottle caps aren't iron or even pure steel so they will not behave as a piece of cast iron or cut nail as far as reject goes. They are basically low carbon mild steel sheet with coatings. And there is a lot of variation. I also find a big difference depending on if they are flattened. You can see in this text that there are 2 types of crown caps: tinplate and tin free steel (TFS). I personally want more finds than less so I want to dig all the bottle caps. Tin can lids are no different. They could be an Eagle breastplate>>>>>>>>.
There are some other tips out there some guys have advocated. One is something that should be done on most targets anyways, that is to check it from a few different sweeps. Often a coin will "lock" & stay at that number from all angles say +24 for example. Rusty caps seem to shoot down up to 10 digits less at times (or into the teens). Guys have said raising the coil can make rusty caps rocket down quite a bit, but not being iron they will never totally go negative. But, a depth check can be helpful too as a tilted or deep coin can go down into the teens as well. Just takes practice & experimentation to see how rusty caps react compared to a coin. I would maybe see what happens with threshold scaled way back to say -35 (just an idea). But it's sorta a double edged sword because you probably want top depth too. So to get deep coins, you may have to endure a few caps. After many, many hours I now find a coin just sounds more crisp as well. Sometimes I don't mind digging 'em out as I feel I'm cleaning out the site & perhaps opening up an opportunity to get something being masked.
Maybe a few others can jump in with their tips too?.....
HH,
Bill
