I am new to the AR rifle, but have been a working mechanic for many years.

I was slightly spooked by some of the stories and problems people have had installing the roll pins.

Here is what worked great for me.  I have an aluminum hammer I made years ago from a scrap of 1" bar stock. Have never had a real use for it, just light tapping when needed.

Let me tell you, it is the cat's ass for installing those roll pins in aluminum.  After rounding and oiling one end of the pin, I just held the pin with a pair of needle nose pliers, and tapped those pins to just short of flush.  The aluminum "grabs" the pin, no slipping off, and no spalling. Just seated the pin with a regular punch, done.

Of course the trigger area had to be well supported.

It worked  for me, now that tool has a job.

That's handy.  Local guy here had a couple of lowers that both had the finish scuffed from trying to knock them in with a claw hammer.  Yikes!

Much of the time I use a hammer with replaceable heads, and use the hardest plastic head available.  It does the same thing, holds the pin, but eventually it chews up the head, then I replace it, cheaply...  My brass hammer heads are also getting chewed up, but better that than what I am smacking.