Thinking of GPX 5000 - Discrimination?

[smgorsch]

Greetings --

I'm new to PI technology and understand that the GPX 5000 has some limited ability to discriminate metal. I recently came into an old 300 acre farm in central Virginia but hunting is hampered by severe ground mineralization. How useful would the ML 5000 be here in searching for coins, recognizing that there's tons of ferrous junk from years of farming implements buried on the property?

thanks

stefan

 

[vtcivilwar]

I recently returned from Culpeper area with my gpx5000. I was there for Civil War relics and it hammered on 58 cal 3 ringers and buttons. I did find a 1862 IH about 10 inches down. It will work just fine on coins. Remember the GPX will error on the side of caution. If you have an iffy signal, deep, that the machine can't ID, it will ID it as non-ferrous. That way you won't loose anything good. I dug a ration can at 30+ inches.. I am no expert but I will put money you will do just fine in VA with the gpx. Good luck..

 

[fredm]

So, VT;
are you saying the 5000 discriminated out the iron nails, bits of cans and other small ferrous junk with accuracy and still found the non-ferrous goodies? my experience with the 2200, gp extreme and my 3500 is that the iron discrimination is useless at depth and not very reliable for most small, flat bits of iron wether deep ot not...

but, perhaps the 5000 really been improved in that regard...

fred

 

[whylee]

I run with discrimination off so I cant help you there, but the GPX is a great machine. You could probably get by just as well with the GPX4800 and save a little cash. If you are going to prospect alot then get the 5000.

 

[smgorsch]

Thanks all

stefan

 

[vtcivilwar]

So, VT;
are you saying the 5000 discriminated out the iron nails, bits of cans and other small ferrous junk with accuracy and still found the non-ferrous goodies? my experience with the 2200, gp extreme and my 3500 is that the iron discrimination is useless at depth and not very reliable for most small, flat bits of iron wether deep ot not...

but, perhaps the 5000 really been improved in that regard...

fred

This was my first time out with a pulse. I did dig iron, it was deep iron. I think it did good and there was no question when I hit a 58 cal or a button. It would sing. If the signal was iffy, I turned and tried it from a different angle. If it was still choppy I walked on. (I did dig them at first). Like I said, if the machine cant positily ID as a ferrous item, it will go into a non-ferrouis tone so you will dig it. That way you don't loose a good relic, thinking it was iron. I dug a lot less iron then others in my group that had a different brand pulse. I am no expert,

 

[alexismex]

What i can see with this post ...it is that the big boss GPX 5000 still have a big recovery of iron metal.... still the army of engineers of minelab did not resolve YET the discrimination of iron !!!!!
That make me without expectation to resolve myself this problem of PI in a century years???
Alexis.

 

[Daniel Tn]

Like someone else noted, if you are getting one for coin and relic hunting, then go for the 4800 or find a new 4500 if you can. I know where two are for sale new, but they are hard to find unless you take a risk on a fake one. The 4800 would be the way to go other wise. You can get them new for around $3800-$3900 if you look in the right places.

I have the 5000 and if I would have only knew then what I know now, I would have stuck with the 4500 or got a 4800 and saved a considerable amount of cash. You aren't going to be able to use the Coin/Relic timing...forget about it. If the ground is mineralized at all, it wont balance in that timing. In fact, I have yet to converse with anyone in the continental US that has been able to balance the machine in Coin/Relic timing. So you are going to be using the same timings that the 4500 has in it anyway with no other real advantage.

As far as iron goes. If it is big iron, the GPXs can do a really good job at discriminating those out. It will simply null out over iron.

When talking about nails and such, it does a good job there to a degree. It all depends on how you have it setup to be honest. It is light years ahead of the TDI when it comes to this. Depending on what timing you are in and what speed you have it set at, you can do fairly well at discriminating out nails. If they are bent they will sometimes fool you if you are digging those iffy signals.

I've found that the GPXs will hit minie balls good down to about a foot deep, and give what I call a "no brainer" signal. Down to 12 inches you are good. It's when you start trying to find them beyond a foot, that it gets tricky, because sometimes the signals wont be as hard hitting as they were shallower and give more iffy signals. I've dug .58 cal minie balls down to 18 inches with it and have dug the .69 cal 3 ringers down to 20 inches. Those are the harder ones to tell from the shallower bullets. The GPX can do it but you're gonna be digging a little bit of deeper nails in the process. If you can dig down a few inches and the signal get worse, it's not a bullet. If you dig down a little and it gets better, jackpot. Watch out though, because shallower bullets will actually overload the detector and make you think it's nulling it out like iron...if you raise the coil a bit and it starts to give a smoother tone it's a shallower target. Iron will still give the broken signal or nulled out signal, pending on how high or low you have the disc set at.

What is needed, is a smaller round DD coil for the GPXs. The 11" is simply too big to work heavily laden iron areas. There aren't many smaller ones offered and most of those are elliptical coils. The little CoilTek Joey coil works well in iron but I think a 6 or 8 inch round DD coil would be the ticket for the GPXs in heavy iron.

 

[ScottTX]

I have used the GPX now at 3 DIV hunts. I have run the discrimination as low as 5 and as high as 10.

At 5 most of the large iron is very discernible. As you cross the target the signal will begin to lift as though it is a good signal then it will null (completely blank out) then signal to background after the target is passed. So basically you get a signal with a blank area in the middle. With this detector you will dig yourself to death. I made friends with several Chinese at the last hunt. With that said, modern nails are no problem but some of the 1800's squares will give a sweet tone. Not a loud 'dig me fool' tone but one of those that says 'ya better dig this it might be good'. So, with disc set at 5 I limited my holes to only good stuff with some squares thrown in. Sometimes you can get a sweet signal the first shovel of dirt will tell you if its good or it will null. If the signal gets louder it's a good target but if it nulls stop digging.

When I first got the detector, being suspicious, I dug everything just to see if the disc was actually working and it was.

Now, with the disc set at 10 you dig very little iron including square nails. If you dig iron you want to.

There is a rule of thumb that I use on nulls. Since most 'bad iron' is recent it will be in that upper 4-6" range. Because of the GPX and its depth advantage I always make my first hole blade deep (12" on my digger). When I sweep the hole If the signal is still good I continue to dig. On the other hand if there is no signal in the hole and I sweep the plug (it will be upside down) and get a null I put the plug back. I have actually used this technique on iron since most of the modern stuff is higher. I found a 1858 Rifle Punch Tool at 14-16". Most of the stuff I found buttons, minies etc. are in the 12+ range.

I have not had the privilege to using the GPX in mild to moderate ground. DanielTN, me and any number of other GPX users are not kidding about the depth this machine will achieve. My deepest signal was 20" in the ground in a fire pit. On the surface the signal was faint until that first shovel came out of the ground. What I heard was a 2" flat piece of camp lead.

If you are hunting an area where you have good clearance and you might suspect there may be artillery shells then I would put the GPX in all metal (Discrimination set to 0) mode and use an 18" mono coil and dig everything.

 

[Jim Robertson]

The only thing I would add is when you find a target be sure to cross over the target from different directions with the coil. There are times this will help you to better understand the target you are standing over. It's not 100% fool proof but it will help you in digging less holes and less junk. Let the target talk to you it will if you lessen. Go slow very slow. Thanks Jim