Late Afternoon Comparision Of GPZ And GPX

[Nevada Brian]

Just recently we were detecting (all experienced detectorist) in the grasslands of California, with two GPZ's, one had the stock 14" coil and the other had the 19" coil and two GPX's one had the 17x13 Evo and the other had the Minelab 12x15.  Towards the end of the day, we decided to perform a test.  We buried about a 9mm slug 14" deep.  I went over the target with my GPZ, HY, Normal, Sen 15, Smoothing Off, and barely heard the target.  Same settings with the 19" but much better results.  Heard the target about three inches above the ground.  Next, the GPX with the Evo coil in Sharp, General, don't remember the gain but a smooth threshold with the gold screamer, and no signal.  The next detector is the one that is really giving me heart burn, the GPX with the 12x15 commander in Sensitive Extra, General, don't remember the gain but a smooth threshold with the stock battery.  It gave an obvious signal about 5 inches above the ground.  I could not believe how loud of a target response this stock GPX gave.

After hearing the results from the GPX, I increased my Sensitiviy to 20, but there was too much ground noise to hear a target.  I also tried different ground and gold modes with the GPZ, but nothing compared to that GPX.  I wish we had more time to really investigate, but we were all tired, and the sun had already set behind the mountain.

Is this just one of those scenarios that we must except and move on, or is there some credibility here???

Has anyone done similar tests or can give some suggestions?

Still scratching my head,

Brian.

[Rick K - First Member]

Lead bullet or jacketed?

[Steve Herschbach]

It does prove the GPX might have an edge when detecting for freshly buried 9mm slugs.

If I am doing serious testing there is only one way I do it. For two detectors:

1. Take detector number one, go find target. Play with settings to get best signal on this found target. This insures you are tuned up properly for this ground.

2. Check same target with second detector. Again adjust settings for best results in this ground.

3. Make notes on responses, dig target, more notes on what it was, depth, etc.

4. Swap detectors, and go find target with the second detector.

5. Cross check with first detector.

6. Repeat for as long and as many targets as it takes to reach reasonable conclusions.

7. Always realize results are only valid for the particular ground and on the particular types of targets found. A totally different location with different mineralization and types of target (gold for instance varies greatly in different places) may yield different results.

This process can take many hours if not days, and can't be rushed. The only thing we want detectors to do is find targets in the ground that usually have been buried a long time. Air tests, test gardens, buried targets etc. all provide some information but in my opinion never substitute for extensive cross testing on found targets.

I am not making excuses here for the GPZ and in fact I have no doubt that for some gold targets a GPX may do a better job. No detector is 100% across the board perfect on all gold nuggets in particular because they occur in almost infinite variety. As a generality the GPZ excels on porous and gnarly, prickly gold. The GPX excels on solid, rounded gold.

Ricks question about jacketed or not is very important. Lead bullets might be a reasonable substitute for gold nuggets but jacketed bullets are more like coin detecting.

[Nevada Brian]

Good information Steve.  I agree, a target buried for a long period of time will make a detector react differently.  This non-scientific test that we did, the results were a bit disconcerting, since I figured the GPZ should win hands down.  I still believe in the GPZ, but now I know its not absolute. 

The bullet was lead.

 

[Steve Herschbach]

Well, get a nice piece of specimen gold. Put it on your buddies GPX coil and show him that no matter the settings it can't pick it up rubbing on the coil. Then show your GPZ pick it up at a foot. Turn about is fair play!

There are no perfect units and in my opinion the Minelab GPX 5000 is still a bang for the buck leader. It can handle salt ground and some hot rocks that the GPZ struggles with and has a coil selection second to none. Nobody with a GPZ should be lording it over a GPX owner. Yet where I hunt and for the gold that remains to be found out there I have every confidence the GPZ is doing the job for me.

[jasong]

Not just bullets, there are some types of gold nuggets that the GPX will actually hear deeper than the GPZ and I've witnessed it both in-situ and replanted myself. They aren't always slugs, they can be porous, tangly bits that you would swear upon seeing that the GPZ should be outperforming on but it doesn't. Another example is low-iron stony meteorites, it's often possible to get much more depth with them on a GPX from the results of my testing, the bigger the stone (200+ grams) the bigger the depth difference as a general trend with outliers.

I've commented about this quite a bit in previous posts. I suspect often it may have been occasionally viewed as negativity rather than being accepted as actual observations though, so I'm glad other people are testing their equipment too.

The 15x12 performance throws me off a bit though, I can't say I've ever seen that much difference in depth between it and the Z14 or it and the 15x13 Evo. Are you certain the operator didn't have metal in his boots or a low hanging pick, or something interfering with the control box in his pocket or something? Was the signal equally strong both directions he swung? Was something like a camera tripod or beer can added onto the ground nearby when that machine was used? I can see a difference on certain targets between 2 different machines using different technology, but between two GPX's using two similar coils it makes me think something may also have been at play?

[Steve Herschbach]

2 hours ago, jasong said:

I've commented about this quite a bit in previous posts. I suspect often it may have been occasionally viewed as negativity rather than being accepted as actual observations though, so I'm glad other people are testing their equipment too.

Not negativity - observations are observations, and yours and others are greatly appreciated Jason.

All ground balancing metal detectors employ various ground balancing methods. Whatever method you choose eliminates responses from certain types of ground and rocks. There will always be types of gold that overlap those rock and ground responses. Therefore any ground balancing metal detector will, repeat, will miss certain types of gold targets. Once you get your head around this fact and accept it then you stop thinking all the gold under the coil is being detected.

Think of the timings on the GPX series. Each timing scheme is designed to eliminate certain ground and salt responses. Anyone that plays around with the GPX can see that changing the timing - in other words changing the ground balance scheme, changes the way the detector responds not just to the ground but to different types of gold.

The GPZ attempts to fill in the "holes" in the GPX timings but does indeed have its own "holes" also. That is just a fact. The only way to eliminate this is to use a non-ground balancing detector. Unfortunately then the ground and all the rocks go beep!

Both GPX and the GPZ also have holes that the SDC 2300 fills and so the SDC can find gold those detectors miss. And a Gold Bug 2 can find gold all those models miss. All you need is a GPX/GPZ/SDC/GB2 and you are all set.

[DolanDave]

Hi Brian,

  Thanks for the testing....

  My main coil for years on the GPX 5000 was the 12X15 commander, that coil has some great punching power, and heavy for its size.  But like Steve says, it would not do to good on Specimen gold, but the GPZ I have now, and been finding out, is a killer on the Speci gold.... 

  Jason, I have been finding some large meteorites with the GPZ that the GPX would not even hear, and they are only a few inches down, not to deep.

  Just neat to hear the different scenario's everyone has. I love comparisons, especially on video.... keep em coming guys..

Dave.

 

[Lunk]

3 hours ago, Steve Herschbach said:

All you need is a GPX/GPZ/SDC/GB2 and you are all set.

Awesome Steve - sounds like a new project for you to work on! Just wondering if you can stuff it all into a light-weight housing...you'll have a winner. ?

[Nevada Brian]

3 hours ago, jasong said:

Not just bullets, there are some types of gold nuggets that the GPX will actually hear deeper than the GPZ and I've witnessed it both in-situ and replanted myself. They aren't always slugs, they can be porous, tangly bits that you would swear upon seeing that the GPZ should be outperforming on but it doesn't. Another example is low-iron stony meteorites, it's often possible to get much more depth with them on a GPX from the results of my testing, the bigger the stone (200+ grams) the bigger the depth difference as a general trend with outliers.

I've commented about this quite a bit in previous posts. I suspect often it may have been occasionally viewed as negativity rather than being accepted as actual observations though, so I'm glad other people are testing their equipment too.

The 15x12 performance throws me off a bit though, I can't say I've ever seen that much difference in depth between it and the Z14 or it and the 15x13 Evo. Are you certain the operator didn't have metal in his boots or a low hanging pick, or something interfering with the control box in his pocket or something? Was the signal equally strong both directions he swung? Was something like a camera tripod or beer can added onto the ground nearby when that machine was used? I can see a difference on certain targets between 2 different machines using different technology, but between two GPX's using two similar coils it makes me think something may also have been at play?

Hi jasong, there was no additional metal added to the equation and the signal was equally strong in both directions. In fact, when the GPX with the 12x15 coil was going over the target, the user removed his headphones and I was amazed as to how loud the signal was.  My buddy Chet was there and maybe he will chime in on this as well.  

That night I watched your video you made comparing the 11x17, 13x17 and GPZ and from what I remember from your video, there wasn't much of a signal difference and that was with a 4500 if I'm correct. Thank you for producing that video. 

We like to do these nonscientific infield comparisons as it allows us to better understand the limitations of our detectors for the ground were detecting.  I just wish we had more time to diagnose our results.  

Brian