Here is some info. about the depth my Cibola gets. The Cibola is not my main hunting machine. I bought it for competition hunting. However, I have some chances to detect with it under other circumstances a lot of times just goofing around and taking up some time. I had some time to burn at a friends and I started to detect. Besides a handful of coins, I found a brass 30-06 shell in low mineralized soil at 9" with it. I measured the depth with a small tape measure I carry with me. I was pretty impressed with it and still am.
I was at a beach competition hunt and didn't bring any of my other detectors with me. (Why I ask myself

) Anyway, I went back to the place I was staying and saw some detectorists working their way up the beach out back. I couldn't resist and had to get out there. I went out and started swinging over the same sand. I got a hit, so I dug a scoop of sand, swept over it and the target wasn't in my scoop. I thought well maybe I didn't pinpoint it well enough. So, I scooped on either side of the hole and the target still wasn't in my scoop. I decided that it must be deeper and took another scoop. Still no target in the scoop. Finally, I took the third scoop and I got the target. The depth of that target had to be well over 6". I repeated this several times and took great satisfaction in picking up coins with a $300 machine that others missed with $800+ detectors. The HOT series of detectors really go deep!
Since the Cibola has a preset ground balance, I would send the main unit and the coil back to the factory to have it tuned. If the ground balance is not correctly set or the coil and main unit not properly tuned, you will not get the depth. However, you will still easily pick up shallow targets. The only other reasons could be the way you are setting up the machine and the way you hunt like the way you swing the coil and your swing speed.
Even though the Cibola has a factory pre-set ground balance, I still ground balance in All Metal. I am not sure this makes a difference but I do it anyway. To do this, I set the sensitivity about 9 o'clock, push the pinpoint (puts the machine in All Metal), turn up the Threshold until I can start to hear it and it is still stable, (keeping the pinpoint pushed in) lower the coil to the ground and try to get a steady sound (no increase or decrease in volume) as it is lowered (not raised from the ground). Some like it HOT so a little increase in volume as you lower the coil isn't a bad thing.