Never noticed it before.  I guess I'm dropping money on the anit-rotational pins.  Does this happen on every AR due to the hammer spring engaging the notch in the pin?  If so I may get two sets.

Rotating pins is pretty common with the AR-15/M16... From long term reports I've read, it doesn't seem to cause any real problems, but if I had a lower I couldn't replace, like a Class 3 or a preban in an occupied state, I think I'd use the anti-rotation pins to play it safe...

Thanks for the answer.  It's a post ban PWA.  Nothing special, but they are no longer made under that name and it's my first so I want it to last.  Lately I keep seeing more upgrades I'd love to get but I need to keep reminding myself I wanted my first build to be simple and cheap.  The pins aren't too much of a stretch in my opinion seeing as they prevent wear.

hammer pin rotation is normal...
a small detent spring in the hammer holds the cross-pin in place so it should not walk out under normal use.