Yeah, lots of different soils throughout a general hunting area...the ONLY time I GB is in this one particular field, high 70's, like 78 I seem to remember...nice deep loam, old silver there, generally 8" deep, and I've got a lot of it out of there...the rest of my spots, totllots, beach, parks/scrapyards...I never GB...on my recently completed Southern run, I did not GB at all...'course, i'm hunting surface to 5" targets, with the low sens...so I dont think it matters as much as if a person was hunting clean ground for deeper older stuff.....as a guy hunts a place where the soil is changing, a guy gets the feel of it and the ever changing soil conditions and then can determine if its necessary...at least thats what I tell myself!
Its probably a good idea to GB often when hunting a big area with ever changing soils/moisture...sure couldn't hurt, but for some reason I just dont do it. I know what the machine is saying in that particular spot...the tone, age and depth of targets start to change for instance...for me, coil control/speed and concentration on what the ground/targets are saying is more important...from a time management standpoint, even though GB only takes maybe 20sec. start adding that up and a guy can get an extra day per year by not fooling with it...
Full disclosure, if anybody is running the F70 incorrectly, its ME,

then again, I'm not hunting deep targets...just clad and gold/silver jewelry, and trying to bang out as many targets in as short a time as possible..so that should be an encouragement to you all that do proper set ups and pay attention!

And a testimony to the F70s forgiveness afield.. I get a high but soft peep, its generally silver past 5"...if I hop coil with no feedback, I run up the sens, hop coil again, and have to whip out my knife to go after it...
Dont know if this helps dude, I am interested in someday hunting with somebody that knows what they are doing and can show me a few things..hopefully your question will engender a great amount of info today...since the dang ground froze again overnight and its snowing..

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Mud