I have some U-shaped brackets that I'm nailing into a 4x4 post. The
brackets will hold a 2x4 stringer. The nailing hole in the bracket is
in the base of the "U", and it's hard to nail the nail without
damaging the surrounding legs of the bracket. I've been using a
nailset. Is there any technique to make this easier or any piece of
equipment that will help? I'm wondering if a framing nailer could
drive a nail right through the metal into the wood.

A framing nailer will *possibly* drive a nail through the metal. Most
likely, the nail will curl up into a coil, then bounce back and put out
your eye. (Your mom did warn you that you could put out an eye, didn't
she? :-) )

Get yourself a palm nailer. You'll wonder how you ever lived without it.

I've seen ads for bracket nailers that let you put the nail accurately
through the holes, but I've never used one.

--
Steve Bell
New Life Home Improvement
Arlington, TX USA