give my take on it for what it's worth...
Iron hunting is very tedious for sure!!!
The machines you mention I also use for iron hunting and they work really well for me...I hardly get no falsing from nail's unless there bent...Dave Johnson really has a good iron I.D. circuit..
But I spend hour's and hours in one spot no bigger than a 15'x15' area picking through these area's....and have for over 20 year's..... some target's that cause you to dig after awhile will probably come as second nature to ignore...
There's no way I could ever work dense iron with a 1266 fisher... it was always a Tesoro back then that picked better...You could work iron with a 1266 but you dug the fool out of all iron over 6 inches deep and alot of surface nail's to boot...the problems you are having with the modern detector is night and day over the older fisher's in iron...
I actually like a machine to sort of get iffy on nails ...that's the way they can unmask adjacent target's.....it's the quality of the signal you are after in iron....it might just be a spit but enough nail spit's will alert you to a different sounding spit or sputter or chirp that has you digging...( Visual Target I.D. in real machine gun rapid fire nails is basically useless) it's all audio in iron....
That's another reason I don't really like tone's when really getting down to hard hunting a spot...the machine like say the T-2 although excellent scares me whenin anything above 1 tone .. the simple reason being the tone break's at a pre-determined point ferrous to non-ferrous is at 40....well lot's of co-located target's will pull below 40 by averaging and just grunt...And 1 tone to me dont seems like it has that good ol disc range like some analog's I have used to really split the nail's the setting on the t-2 being around 21 but there either there or not not enough in between iffy nuanced style nail signature I cut my teeth on...
Some machines for one reason or another cant deal with the scenario well...I have a detector that is struggling with this issue on the simple bases of just to good of a false to discern it from a legit hit...
if you think the Tek's are tuff in iron try a AT-Pro in the nails and you will really chase signal's....( but you would probably make some great finds in the process)
You mention the 180 target check.......Well that works better on isolated target's than it does on the iron infested site's because you might be getting that particular signal at the only angle it can sound off...
Remember the nails you are digging or getting hit's on are just a fraction of the ones that are being rejected perfectly ....
(It's the stuff I cant hear that scare's me..)
I know it is a hard way to hunt but that's the area's the other's also avoid,,,because of the same reason's you have mentioned...
If you could see all the iron trash in a spot just lifted out of the ground at let hover for a minute in the air in would probably discourage you from even hunting the site...
1 surface nail can mask a true prize be it a Confederate belt buckle a foot deep under it or a rare 200 year old gold coin or big silver dollar...
Iron is a challenge and you have to be up to the task...BUT being in perfect unison with your machine to the best of your ability and having a machine you are confident with to work the iron is very important for success... Some times you just dont never click with a machine the next guy does wonder's with...
Never knew something so fun could be so hard Ha-HA...
once you get into the realm you are getting into now you are passing the hobby stage and it's starting to become a skilled form and the detector is a tool that is just as important as any craftsman tool he uses to work his magic...
we too can do wonderful thing's with our detector's...
It does not take a 1500.00 machine to unmask better than a 200.00 machine it's still 75% operator and being in total harmony and having an understanding of all aspect's of the nail hunting art.
Sorry for the long post probably more than you wanted to hear and I am exchanging information you may already know..
Keith