Re: Which coils do you use most often?
UPDATE: After reading all the great suggestions, I ordered the 10" DD Excelerator from Kellyco. They have a serious backlog in orders and it took me three months to receive the order. Ouch! Kellyco apologized for the delay and waived the fee for shipping. That was good of them. At least the delay occurred in the summer, when the heat and hard ground usually keep me away from swinging the M6.
After using the new 10" Excelerator coil once for about an hour, I am thrilled with the results. I went back to an early 1800s home that I've searched to death with the stock coil. Recent trips had not turned up much at all and I was considering abandoning the site. My hope was that a new coil would breathe new life into a very productive old place.
The first thing I noticed was the additional signals I was hearing-- from areas that were searched many times before. In one hour I recovered three nice targets that were previously missed: a dateless two cent piece (my first), my first silver thimble (which I gave to the homeowner), and a child's ring. The two cent piece was 8-9" deep. It gave a light, yet solid signal from two directions. I agree with jcooking, the 10" DD Excelerator gives additional depth as well as better coverage than the stock 9.5" coil. How much deeper? I'm not sure, but I would guess an inch or two. And as advertised, it does seem to pick out good targets that are hidden amongst the iron.
I really need to get better at pinpointing. With the M6 stock coil pinpointing was always dead on. So far I am not comfortable with pinpointing with the 10" Excelerator, but I guess that will take time.
I'm really excited about getting back to this one acre site and going over it inch by inch!