If you're using the 11x8 Widescan, there's not much you can do except to run disc higher..or switch to a concentric coil. The iron will give a shorter duration, scratchier signal, then start with popping and clicking, as you go higher with the discrimination...'till it's gone. By then, nickels and small gold may be disc'ed out as well.
Best way to
avoid small iron though? Ask your Bandido that question..
Pretty sure your Bandido would have passed over that nail while still sounding off on a nickel under the coil, at the same time. I think the Vaquero will always have a little harder time rejecting the iron than the Bandido has with it, no matter which coil you use..but concentrics sure do help there. Bandidos are "the stuff" in iron.
The coil that seems to work
best on the Vaquero for disc'ing out metals where they're marked on the faceplate (on my Vaqueros, anyway), is the 5.75 concentric. I think it's a "must have" coil, for any land Tesoro.
The 11x8 Widescan (if you have that one) is nice for coverage, light weight, well made and sensitive.. but it's not the best in trash, especially when you want to disc out iron.