I'v had my 540 pro pack for 8 mos. I started out strictly using the 8" coil because I had very little MD experience. I was loaned an older, Whites machine my nephew had and using a knock-off carrot pointer and dug far too many large "excavations". When buying the 540, I figured if the target was anywhere within the footprint of that V8" coil, that would cut my digging in half!
Well my first trip out with the 540 and V8 coil I dug an IHP at 8" deep in hard packed soil. I quickly got the hang of the 540's built-in pin-pointer and that cut way down on the size of my plugs. I was consistently locating stuff at depths from 8" - 10". You will definitely pick up lots of deep targets and yes this will include iron, especially old nails and bolts.
I hunt with two partners both of whom use Nox 800's. They were impressed with the 540's depth but insisted I would do much better with the V12 coil in open ground. So I took the V8 off and started with the V12. I struggled with the V12 the first time out and seemed to be returning to digging large holes, apparently I had not yet mastered the pin-pointing with the V12 coil. About mid-day I took it off and put the V8 coil back on because we were on a prime old homestead and time was flying. I quickly dug a G.A.R. 1892 encampment medal at 12" deep. The medal was made of aluminum and the signal was banging at 12" deep. I almost discarded the medal at first because it was unidentifiable. It looked so much like a token or coin I thought I better hold on to it and only after cleaning it some did I realize what I had.
Eventually, I learned to use the 12" coil and can pin-point very accurately with it too. I have dug targets as deep as 14" with the V12 coil including an 1864 - 2 Cent piece found 13" down, again in hard packed clay type soil.
I like the V8 coil for swinging in the woods now mostly. I may try it on the beach this year as well. The V12 was tough on the beach because the target seems to keep moving around and is tough to find. I was lucky to find a 10K gold ring on the beach with the V12 so I'm not complaining. I regularly switch both coils out depending on where I'm hunting. The best way to figure things out is to be out there doing it as much as possible.
I guess where I'm going here is; each coil has a place in the arsenal which brings me to the V10. I think the V10 might be the ultimate all-around coil which could eliminate the need to change coils so frequently. I will be buying the 10" very soon and will report after trying it out.
By the way, I have held my own with the 540 up against my two partner's 800's sometimes even doing better at the tailgate wrap-up. The Nox 800 will likely be my next detector but I'm not in any hurry and I don't think I could have picked a better first machine.
