The range of 10 to 17 is a pretty wide range and I have to agree with Dan and Shagger that you WILL miss good targets if you were to reject that range. If you are hell-bent on doing that, I would say narrow it down a bit. Forget where ALL KINDS of shotgun cases register at and decide where MOST of them read. Then reject that range or those particular numbers. If you're finding a lot of shotgun cases that are at 17 and some that are at 13 then just reject 13 and 17. Do that by using the left/right arrow (-/+ keys) to move your cursor to the 17 and hit the Accept/Reject touchpad to make that one segment go black. Repeat that for 13. Of course if you wanted to you could do that for 10 through 17, but you will surely miss many a button and any number of coins including some gold items...probably MOST gold items. So I like the idea of narrowing it down a bit better. My best advice is to run it in Relic mode and learn through experience what to dig and what not to dig for your area based on the tones and the numbers. It takes some time but it WILL come. Of course the more items you have "Notched out" or rejected, the more the Quattro will "null out" as you go over those items. To me, excessive nulling is more of a pain in the butt than listening to the sounds of the things you don't want to dig and just not digging them. At least you can hunt a little faster and smoother.
Also, in hunting fields, which are normally fairly clean, I think you should wean yourself off of "Auto" and open it up a little. I'm thinking maybe as high as 18 but if it falses, then back it down to 17 or 16...whatever runs stable. Don't be afraid to experiment with it.