Dunno. My Garrett 9x12 coil has no problems with small objects. It will detect BB sized metal no problem at all.
Probably even smaller..
The issue is it sees too much area at one time if over a busy area. So if there are many of those small objects,
it can be a real pain to tell what is what, and which one to dig. It can be done, but it takes a lot longer than using a
small coil which sees much less at one time.
You can use the twitch ID method when pinpointing with the big coil to get an idea on the ID of the particular small
object in a field of many, but it's much quicker with the sniper. With it, you just pop, pop, pop, each one as you
come across it with no need to seperate it out of a large mass of many objects.
BTW, the "twitch" method is pinpointing with the pinpoint mode, and then when you think you are over the object you
want, you release the pinpoint button, and then give the coil a quick wrist twitch in ID mode, just barely moving the coil.
It will then usually ID the particular object you were just pinponting.
You likely already know this, but thought I'd save the newer hunters from having to ask me what I'm talking about..