Its a collar to adjust driving depth, it doesn't just unscrew, but I bet it will come out when those two pins are removed.
That black collar looks like it might be a nut ???
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I looked at mine. looks like your drive pin is extended out. am pretty sure if you tap the center inwards it will move back to the return position and the nail should fall out .
I looked at mine. looks like your drive pin is extended out. am pretty sure if you tap the center inwards it will move back to the return position and the nail should fall out .
